3. Adult Reconstruction (Hip & Knee) MCQs

Rifampin has unique properties allowing it to penetrate biofilms and effectively kill stationary-phase staphylococci. It is a cornerstone of therapy in DAIR procedures for staphylococcal PJI. However, it must always be used in combination with another active antibiotic (often a fluoroquinolone) because monotherapy leads to rapid emergence of rifampin resistance.

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. The synovial fluid alpha-defensin test has been incorporated into the ICM criteria as a highly sensitive and specific biomarker for diagnosing periprosthetic joint infection, regardless of prior antibiotic use or systemic inflammation.

Intra-articular retained bullets must be surgically removed. If left inside a synovial joint, synovial fluid dissolves the lead, risking systemic lead toxicity (plumbism) and mechanical destruction of the articular cartilage.

DISCUSSIONThe complication associated with pelvic radiation prior to cementless THA is loosening of the acetabular component or postsurgical noningrowth of the component. Although scarring from radiation may put the hip at increased risk for arterial or nerve damage or infection, this risk has not been associated with pelvic radiation. Cementless acetabular components with porous metal surfaces such as trabecular metal should be considered.

Although the patient is young, a total hip arthroplasty will provide pain relief and improve her range of motion. The arthritis is too advanced for the patient to benefit from an osteotomy. In addition, periacetabular osteotomy and hip arthrodesis do not improve range of motion of the hip. It has not been established that patients with severe osteoarthritis will benefit from arthroscopic debridement of the hip.

unicompartmental arthroplasty. The absence of an ACL is a contraindication for mobile-bearing UKA.OrthoCash 2020Which of the following is the most common cause of early revision surgery (<20 weeks) following a hip resurfacing arthroplasty?Periprosthetic fractureRupture of abductorsDislocationHeterotopic ossificationPost-operative stiffnessPeriprosthetic fracture, specifically femoral neck fracture, is the most common cause of early revision less than 20 weeks following surgery.The rate of femoral neck fractures following hip resurfacing varies, but most literature reports a rate of 1%. A majority of these fractures happen in the early post-operative period and are the most frequent cause of revision surgery within several months following surgery. The cause is usually multifactorial, but placing the femoral implant in varus, osteonecrosis, and notching have been proven risk factors for fracture.Little el al. report on 377 patients undergoing hip resurfacing. 13 required revision including 8 for fracture of the femoral neck and 3 for loosening of a component. Evidence of osteonecrosis was seen in two of these cases, leading the authors to believe it may contributed to fracture.Illustration A shows a comparison of a typical total hip replacement and a hip resurfacing arthroplasty. Illustration B shows notching of the femoral neck, a known cause of femoral neck fracture following hip resurfacing. Illustration C shows a femoral neck fracture in a patient with a hip resurfacing.OrthoCash 2020A 55-year-old male undergoes a revision total knee arthroplasty of an implant that is only 3 years old. At the time of surgery, the tibial polyethylene liner shows catastrophic delamination and cracking. What is the most likely cause of this extensive, accelerated wear of the polyethylene liner?Sterilization in ethylene oxideGamma irradiation of the polyethylene liner in the presence of airGamma irradiation of the polyethylene liner with vacuum packagingGamma irradiation of the polyethylene liner in nitrogenGamma irradiation of the polyethylene liner in argonCorrent answer: 2Irradiation of polyethylene in air (i.e. oxygen present) has been shown to be a risk factor for catastrophic failure after total knee replacement.Free radicals are generated when polyethylene is irradiated in the presence of air. Initially, these free radicals result in cross-linking. However, if the polyethylene is exposed to these free radicals for an extended period of time, delamination, cracking, and catastrophic failure may ensue. The industry has completely abandoned this method of sterilization as a result. Currently, the standard of care is irradiation of polyethylene in an inert gas (e.g. argon, nitrogen or vacuum packaging). The amount of oxidative products when polyethylene is sterilized in the absence of oxygen is much less and does not lead to catastrophic failure.Sterilization without irradiation is another option (ethylene oxide). When this occurs, there is no cross-linking and thus the increased wear properties are lost. However, since there is no oxidization, you do not have the risk of catastrophic failure as seen in those liners irradiated in the presence of oxygen.The cited reference by McNulty et al. from Orthopedics discusses the influence of sterilization methods on wear performance. They found that gamma irradiation and storage of the polyethylene components in an essentially oxygen-free environment imparted by gamma irradiation in a vacuum foil pouch (GVF) protects the components from oxidization.Illustration A shows a polyethylene liner that has undergone catastrophic wear as a result of irradiation in the presence of oxygen.Incorrect Answers:catastrophic wear, although wear properties are less than gamma irradiation in the absence of air.OrthoCash 2020Which of the following interventions reduces osteolysis around distal portion of the femoral stem when performing a total hip arthroplasty?Use of an extended offset femoral neck componentUse of a proximal circumferentially coated ingrowth stemUse of a collared stemUse of a long femoral stemEnsuring that the stem fills the diaphysis of the femurCorrent answer: 2Osteolysis of the femur is caused by activation of macrophages by microscopic polyethylene particles within the "effective joint space", defined as any area where joint fluid can come into contact with bone. This can occur above the acetabular cup, through screw holes, and down the femoral shaft around the prosthetic stem. Ideally, with a cementless stem, both the proximal and metaphyseal femur are well filled by the prosthesis. Collared stems are used to augment poor calcar bone quality or bone loss.Sinha et al showed in a retrospective review of 101 hips with cementless circumferentially coated femoral stems no distal femur osteolysis occurred, but 82% showed “evidence of proximal femur stress shielding”, though only 38% showed proximal femoral osteolysis.OrthoCash 2020During a minimally invasive approach to total hip arthroplasty a femoral periprosthetic fracture occurs. Which of the following steps is crucial to properly treat this complication?Transitioning to an extensile approach to adequately visualize and reduce the fractureLimiting post-operative weight bearingSwitching to a cemented femoral stem to avoid the stresses created during press-fit fixationDelaying the arthroplasty until the fracture has healedSupplementing the fracture with autograftCorrent answer: 1Proper treatment of an intraoperative femoral fracture during total hip arthroplasty involves adequate exposure, anatomic reduction, and bypassing the fracture site by 2 cortical diameters of the femur with a long stem. This may involve repositioning the patient on the table if the arthroplasty is performed in the supine position. Minimally invasive surgical techniques have been developed to insert the components through smaller exposures and less soft tissue dissection. The purported advantages include faster rehabilitation, less blood loss, shorter hospital stays, and better cosmesis. However, complications an arise if the surgeon sacrifices surgical exposure and visualization.Fehring et al review 3 cases of total hip arthroplasty performed through minimally invasive techniques with catastrophic outcomes. Intra-operative fracture, chronic instability, and death were all identified.OrthoCash 2020A 70-year-old man underwent total hip arthroplasty 4 months ago and has experienced 3 dislocations. Radiographs reveal no failure of the hardware and an acetabular component that has an abductionangle of 40 degrees and a version of 10 degrees retroverted. What is the most appropriate treatment for the recurrent dislocations?hip abduction bracerevision of the acetabular liner to a constrained typerevision of the entire acetabular componentrevision of the femoral head to a larger sizerevision to an extended offset prosthesisCorrent answer: 3Per Dorr et al: post-operative hip instability can be caused by several factors: soft tissue imbalance, component malposition, or position. Component malposition, as in this case, should be treated with revision of the offending component. In this case the acetabulum was placed in retroversion when it should have been 15-20 degrees anteverted. None of the other options addresses the cause of the instability. According to Morrey, the most signficant risk factors to instability are prior hip surgery, trochanteric nonunion, and posterior surgical approach. He wrote that the most reliable way to correct instability is to reorient a retroverted acetabular cup.OrthoCash 2020In patients with sickle cell disease and asymptomatic osteonecrosis of the femoral head identified with magnetic resonance imaging, what percentage will eventually go on to femoral head collapse?

DISCUSSION: Severe valgus deformity is frequently accompanied by hypoplasia of the lateral femoral condyle. Posterior referencing instrumentation can substantially internally rotate the femoral component with respect to the transepicondylar axis and Whiteside’s line. The femoral component malrotation must be corrected to properly address this problem.

Instability is a leading cause of failure following total knee arthroplasty. Instability can present as global instability, extension gap (varus/valgus) instability, or flexion gap (anterior/posterior) instability. The radiograph reveals anterior/posterior instability with dislocation consistent with flexion gap instability. A loose flexion gap can allow the femoral component to ride above the tibial cam post mechanism, resulting in dislocation. Distal femoral augments treat extension gap instability, whereas tibial augments can treat both flexion and extension gap instability. Posterior condyle augments at the distal femur can also be used to treat flexion gap instability.

OrthoCash 2020A 66-year-old patient is planning to undergo a right total knee arthroplasty. Figure A demonstrates the preoperative radiograph. Placing the components in a kinematic alignment (compared to neutral mechanical alignment) would result in which of the following?Increased aseptic looseningVarus tibial cuts and valgus femoral cutsLower rates of patient satisfactionDecreased ROMIncreased reoperation rateKinematic alignment total knee arthroplasty is based on component placement to recreate a patient's natural anatomy. In the case of this patient, this would involve varus tibial cuts and valgus femoral cuts.Kinematic alignment total knee arthroplasty is based on the principle of re-establishing a patient's natural anatomy. Many patients develop constitutionally varus or valgus knee alignment, in which placement of the arthroplasty components in relative varus or valgus positions would lead to symmetric mediolateral loading of the implants. This principle is further based on the idea that placing the components in neutral alignment may align the limb in an abnormal position to the patient, which may lower patient satisfaction. For varus knees, this implies varus tibial cuts with valgus femoral cuts.Bellemans et al. performed an observational study of 250 asymptomatic study participant to determine what percentage of the population has constitutionally varus knee alignment. The authors found that 32% of males and 17.2% of females had constitutionally varus aligned knees. Furthermore, constitutionally varus knees were associated with greater physical activity during the second decade of life, believed to be secondary to Heuter-Volkmann loading of the open physis.Lee et al. performed a systematic review of the literature comparing neutral alignment and kinematic alignment arthroplasty. Generally, the literature supported that ROM, KSS and WOMAC scores were equivalent, if not better, in kinematically aligned knees. Further, tibial components were in more varus and femoral components in more valgus. There were no differences in reoperation rates.Figure A demonstrates a mechanical axis view radiograph with varus alignment of bilateral knees and medial compartment osteoarthritis. Illustration A demonstrates the difference in bone cuts between neutral alignment and kinematic alignment arthroplasty.Incorrect Answers:OrthoCash 2020A 68-year-old patient with diabetes progressively worsening left knee pain of 6 months duration. They underwent a left total knee arthroplasty 7 years ago. Figures A-B demonstrate the current radiographs. Aspiration of the left knee demonstrated 11,500 WBCs and 94% neutrophils. Aspiration cultures grew methicillin-resistant Staphylococcus aureus. What would be the best treatment approach for this patient?Knee arthrodesisLong-term antibiotic suppressionOne-stage revision arthroplastyTwo-stage revision arthroplastyAbove knee amputationCorrent answer: 4The patient has several medical comorbidities and is presenting with a chronic prosthetic joint infection with a virulent organism (MRSA). The best treatment option at this time would be a two-stage revision arthroplasty.Chronic prosthetic joint infections occur greater than 3-6 weeks from surgery and result in biofilm formation over the prosthesis, making antibiotic treatment alone ineffective for infection eradication. Diagnosis is based on the MSIS criteria, with chronic infections being suggested with CRP greater than 10, ESR greater than 30, and synovial WBCs greater than 1,100. Two-stage revision arthroplasty is the current gold standard in the United States for treating chronic prosthetic joint infections.Kuzyk et al. 2014 reviewed two-stage revision arthroplasty for chronic periprosthetic joint infections. The authors stated that there is no consensus on laboratory and histology criteria to confirm eradication prior to proceeding with the second stage. The authors recommend holding IV antibiotics for two weeks and repeated inflammatory markers to evaluate whether to proceed with the second stage and to perform frozen section at the time of the procedure.Nguyen et al. 2016 reviewed one-stage revision arthroplasty for the treatment of periprosthetic joint infections. The authors reported that in select patients, one-stage revision arthroplasty can have equal if not better outcomes compared to two-stage revision with less surgical morbidity and improved functional outcomes. They concluded that one-stage revision arthroplasty can be successful in patients that are not immunocompromised, minimal medical comorbidities, known pathogen prior to surgery, non-polymicrobial, no virulent pathogen (MRSA), and with good soft tissue coverage.Figures A and B demonstrate AP and lateral radiographs of the right with radiolucencies present around the tibial and femoral prosthesis. Illustration A demonstrates a treatment algorithm proposed by Kuzyk et al. for proceeding with the second stage of a two-stage revision. Illustration B demonstrates the Musculoskeletal Infection Society diagnostic criteria for a prosthetic joint infection. Illustration C depicts specific lab values for diagnosing a prosthetic joint infection.Incorrect Answers:OrthoCash 2020A 77-year-old patient presents with progressively worsening right hip pain and limp. The patient underwent a right revision total hip arthroplasty 15 years ago and is now unable to ambulate due to the pain and feels as if the hip is unstable. The patient's radiograph is shown in Figure 1. Which of the following is the appropriate classification and best treatment approach for this patient?Paprosky 2A; multihole cup with posterior column platingPaprosky 2B; antiprotrusio cage with structural allograftPaprosky 3A; distraction arthroplastyPaprosky 3B; custom triflange cupPaprosky 3B; cemented cupCorrent answer: 4The patient is presenting with pelvic discontinuity due to severe acetabular bone loss and superomedial cup migration consistent with Paprosky 3Bacetabular deficiency and pelvic discontinuity. Revision to a custom triflange cup would be a viable treatment approach.Pelvic discontinuity in revision total hip arthroplasty is a rare treatment challenge due to extensive bone loss from osteolysis and prior surgery. Typically, the cup migrates superomedial towards the pelvic viscera and can place neurovascular structures at greater risk. This defect is classified as type 3B in the Paprosky classification. Treatment involves restoring pelvic stability through the healing of the anterior and posterior columns as well as reconstituting hip biomechanics with custom triflange cups, posterior column plating, distraction arthroplasty, or augments with highly porous cups.Taunton et al. performed a multicenter retrospective review of 57 patients that underwent reconstruction of pelvic discontinuity with a custom triflange cup.The authors found that 81% of patients had a stable implant and healed discontinuity at final follow-up with implant cost being comparable to off-the-shelf options. The authors concluded that that custom triflange cup provides adequate fixation with good outcomes at a comparable cost to other fixation methods.Jenkins et al. performed a retrospective review of 58 hips, of which 11 had pelvic discontinuity, that underwent revision with a tantalum porous cup and augments. The authors reported a high rate of radiolucency in Delee and Charnley zone III and implant failure in patients with pre-operative pelvic discontinuity that were revised with this technique. The authors recommend the use of alternative or adjunctive fixation in patients with pelvic discontinuity.Regis et al. performed a retrospective review of 18 patients that underwent revision with antiprotrusio cage and bulk allograft for pelvic discontinuity. The authors found a 72.2% survival rate at 16.6 years with cases of failure demonstrating graft resorption and acetabular loosening. The authors suggested that bulk allografting with antiprotrusio cages provide an effective means to address pelvic discontinuity.Figure A demonstrates an AP radiograph of the pelvis with pelvic discontinuity. Illustration A depicts the Paprosky classification system. Illustration B depicts the DeLee and Charley as well as the Gruen zones.Incorrect Answers:pelvic discontinuity in such a manner to allow for healing of the anterior and posterior columns. Furthermore, cemented cups are associated with high loosening rates.OrthoCash 2020A 75-year-old male sustains a ground-level fall while ambulating at home. The patient has been optimized for surgical intervention. Both prosthetic components are deemed to be stable. How would you classify this fracture and what is the appropriate treatment plan?Vancouver B1; ORIF with a lateral locking plateVancouver C; revision of femoral stem from hip componentVancouver C; retrograde intramedullary nailVancouver B2; revision to long stem total knee componentVancouver C; ORIF with a lateral locking plateCorrent answer: 5This patient has a Vancouver C periprosthetic fracture about stable total hip and knee arthroplasties (an interprosthetic fracture) which can be appropriately fixed with a lateral locked plate spanning the entire femur.The success of prosthetic surgery has led to an increase in the percentage of the population having more than one prosthetic implant. This, combined with an increase in the average life expectancy and functional requirements for the elderly, has led to a higher incidence of periprosthetic and interprosthetic fractures. Treatment must be determined and assessed according to the type of fracture, the stability of the prosthesis, the bone quality and the general condition of the patient. When the implants are stable plate fixation spanning both of the prostheses has shown favorable results. Some surgeons advocate for nail/plate combination fixation in these interprosthetic fractures in an attempt to allow early weight-bearing.Froberg et al. reviewed 60 consecutive periprosthetic Vancouver B1 or C fractures, all fixed with plate osteosynthesis. There were a total of 8 reoperations, 4 of which were for infection and 3 for fixation failure. They conclude that locking-plate osteosynthesis of periprosthetic Vancouver type B1 and C fractures gives good results in terms of fracture union. It appears that spanning of the prosthesis to avoid stress-rising areas is important for successful treatment. Infection remains the major cause of failure.Hoffmann et al. reviewed interprosthetic femoral fractures, defined as fractures between an ipsilateral total knee and hip arthroplasty. 27 patients were designated as having interprosthetic fractures and were treated with locked plating. They conclude that locked plating can achieve satisfactory results. Additional soft tissue damage can be prevented by submuscular plate insertion. Treatment of type B fractures resulted in significantly greater nonunion rate.Matlovich et al. reviewed fifty-seven patients treated for supracondylar periprosthetic femur fracture with either a locking plate (n = 38) or IM nail (n= 19). There was no statistical difference between groups in the meantime to fully weight bear, the incidence of postoperative pain, range of motion, use of gait aids, time to full radiographic union, or the overall radiographic alignment of a healed fracture. Despite this, they add caution is recommended in using IM nails for fractures below the flange where limited fixation may increase the risk of nonunion.Figure A demonstrates a Vancouver C interprosthetic fracture with well-fixed total hip and knee components.Illustration A is an example of another patient status-post ORIF of an interprosthetic femur fracture.Incorrect answers:OrthoCash 2020A 61-year-old man with left hip OA presents to clinic for persistent left hip pain despite a trial of conservative therapy. The decision is made to proceed with total hip arthroplasty via a direct anterior approach. Which of the following correctly describes the superficial internervous plane of this approach?Rectus femoris (femoral n.) & tensor fascia lata (superior gluteal n.)Tensor fascia lata (femoral n.) & sartorius (superior gluteal n.)Rectus femoris (femoral n.) & gluteus medius (superior gluteal n.)Sartorius (femoral n.) & gluteus medius (superior gluteal n.)Sartorius (femoral n.) & tensor fascia lata (superior gluteal n.)Corrent answer: 5The direct anterior approach to the hip is performed using the internervous interval between the sartorius (femoral n.) and tensor fascia lata (superior gluteal n.) superficially.Total hip arthroplasty using a direct anterior approach has become increasinglypopular, with many studies showing good long-term results. It is performed through the internervous plane between the femoral nerve and superior gluteal nerve, superficially between the sartorius and TFL, and deep between the rectus femoris and gluteus medius. Advantages of the direct anterior approach include preservation of the abductor mechanism and decreased dislocation rates compared to the posterior approach. However, this approach has a steep learning curve and its use is limited in obese patients with a large pannus. Additionally, this approach places the lateral femoral cutaneous nerve at risk and may lead to increased intraoperative fracture rates.Bohler et al. published a review on the direct anterior approach to the hip. They report that this approach allows for direct visualization of the acetabulum and offers a complete intermuscular and internervous access to the hip joint.They found that the approach allows for decreased muscular trauma, intraoperative blood loss, and post-operative rehabilitation.Post et al. published a review on the indications, technique, and results of the direct anterior approach for THA. They report that the steep learning curve and complications unique to this approach (fractures and nerve damage) have been well described; however, the incidence of these complications decreases with greater surgeon experience.Illustration A is a diagram depicting the superficial internervous plane of the direct anterior approach to the hip.Incorrect Answers:OrthoCash 2020A 45-year-old male presents with increasing left groin pain. He has a history of bilateral hip avascular necrosis and underwent bilateral hip resurfacing arthroplasties 3 years ago. He is a recreational runner and recently ran a 10-kilometer race several weeks ago. Figure A demonstrates an AP radiograph of his pelvis. Serum testing demonstrated a cobalt level of 10 mcg/L (reference 0.8- 5.1 mcg/L) and chromium level of 7 mcg/L (reference 0.5 - 2.5 mcg/L). What is the likely cause of the patient's symptoms?Iliopsoas tendonitisEdge-loadingProsthetic joint infectionIncreased activity-related wearFemoral neck stress fractureCorrent answer: 2The patient is presenting with increased left hip pain after bilateral Birmingham Hip Resurfacing (BHR) arthroplasties and elevated ion levels consistent with metallosis. The most likely cause of metallosis in this patient is the edge-loading of the implant.Hip resurfacing arthroplasty is a bone preserving procedure that is favorable in young male patients and utilizes metal-on-metal articulations. Metallosis is, therefore, a concerning complication of these implants and can result in pseudotumor formation and subsequent destruction of the hip abductors.Patients presenting with a painful prosthesis should be screened with metal ion levels as well as a metal artifact reduction sequence MRI. Possible causes of metallosis include edge-loading, component malpositioning, third bodywear, impingement, and sensitivity to cobalt.Brooks performed a retrospective review of patients undergoing BHR with regards to outcomes. The author found a 0.23% rate of metallosis in the study population, with all cases being attributed to edge-loading. The author recommended a preoperative CT scan and lateral pelvic radiographs to prevent component malposition and better identify surgical candidates.Matharu et al. performed a prospective cohort study examining metal ion levels in patients with bilateral BHRs. The authors found that cobalt, chromium, cobalt-chromium ratio, and maximum cobalt and chromium levels to be significantly higher in patients with metallosis. They recommended using a cut-off of 5.7 mcg/L for cobalt and 5.5 mcg/L for chromium for metallosis in patients with bilateral BHRs.Figure A demonstrates an AP radiograph of a pelvis with bilateral BHR implants and an increased inclination angle of the left acetabular component.Incorrect Answers:OrthoCash 2020An ambulatory 57-year-old man with post-polio syndrome presents for follow-up of his right knee pain. He has failed all nonoperative measures for his right knee pain. On exam, he hyperextends to 15° and flexes to 120° with global instability of the knee. He has maintained antigravity strength in the right limb. Radiographs are shown in Figures A and B. What is the best treatment option for this patient?Cruciate retaining knee with ligamentous reconstructionRobotic-assisted posterior stabilized total knee arthroplastyDistal femoral osteotomy with total knee arthroplastyHinged total knee arthroplastyAbove-knee amputationThe best treatment for this patient with post-polio syndrome is a hinged total knee arthroplasty.Patients affected by the 1950 poliomyelitis outbreak are now approaching an age where degenerative knee changes are impacting their quality of life. These patients often have global instability and significant hyperextension deformity and require a hinged prosthesis. Any less constrained components put the patient at risk for continued instability and early failure. Patients with maintained antigravity strength in the operative limb may have improved outcomes in the setting of post-polio syndrome.Gan et al. reviewed 16 knee replacement in patients with post-polio syndrome and degenerative knee changes. They found an improvement in the mean of all outcomes scoring measures including the AKSS, Oxford knee scores, AKSS pain scores, and SF-36 scoring. They concluded that primary knee arthroplasty for patients with post-polio syndrome shows a good improvement in patients quality of life and decreases pain.Giori et al. retrospectively reviewed 16 patients with a history of poliomyelitis and a history of primary total knee arthroplasty. They found four cases of recurrent instability, two of which had a preoperative hyperextension deformity of 20 degrees. They concluded that pain and knee scores improved in these patients and that recurrent instability or functional deterioration occurred more often in the most severely affected knees. They recommend consideration of hinged arthroplasty or arthrodesis in this challenging subgroup of patients.Figures A and B are AP and lateral radiographs of the right knee showing and severe valgus-hyperextension deformity and degenerative changes in a post-polio limb. Illustrations A and B show an AP and lateral postoperative radiograph following a hinged arthroplasty.Incorrect Answers:OrthoCash 2020When compared to a median parapatellar approach which of the following approaches may lead to higher rates of component malposition?Quadriceps sparingLateral parapatellarMidvastusQuadriceps snipV-Y turndownA quadriceps-sparing approach has been found to lead to a high rate of component malpositioning.Improvements in surgical instrumentation and techniques drove surgeons to perform total knees replacement in a less invasive manner. One such technique was the quadriceps-sparing approach which uses minimal subluxation of the patella and special side cutting instruments. This technique was thought to lead to quicker recovery due to the minimal disturbance of the extensor mechanism however, studies have shown that it may lead to statistically significant higher rates of component malposition when compared to a traditional median parapatellar approach.Kazarian et al. reviewed the outcomes of the quadriceps-sparing (QS) approach compared to a median parapatellar(MP) approach for total knee arthroplasty. They found statistically and clinically significant disadvantages to the QS approach including femoral and mechanical axis outliers, increased surgical time, and increased tourniquet time. They concluded the QS approach does not demonstrate any clinically significant advantages and leads to higher rates of component malalignment.Kelly et al. randomized 42 consecutive total knee patients to either median parapatellar (MP) approach or a vastus splitting (VS) approach. They found a statistically significant increase in the rate of lateral release and blood loss in the MP approach but showed no difference in functional parameters, tourniquet time, or patellar resurfacing. They conclude the VS approach is a reasonable alternative to the MP approach and may lead to lower rates of lateral releases without impairment of quadriceps function.Liu et al. compared outcomes of the minimally invasive midvastus (MV) andsubvastus (SV) approaches compared to a traditional median parapatellar (MP) approach for total knee arthroplasty. They found the number of days needed to perform a straight leg raise was significantly longer following MP compared to SV or MV approaches. They conclude that further studies should be performed to assess the outcomes of the various minimally invasive approaches for total knee arthroplasty.Illustration A shows four different approaches for a total knee arthroplasty including three minimally invasive approaches.Incorrect Answers:OrthoCash 2020A 66-year-old patient that underwent a right total knee arthroplasty approximately 4 years ago presents with worsening right knee pain over the last 48 hours. The patient has a history of rheumatoid arthritis and recently underwent a dental procedure a week ago. Labs were significant for CRP of 212, ESR 105, and a WBC count of 11K. Aspiration yielded a milky-looking fluid with 55K nucleated cells with 97% PMN. Radiographs are shown in Figures A and B. What is the next best step?Surgical intervention after cultures finalizeRepeat aspiration of the knee and send for alpha-defensinBegin IV antibiotics and re-evaluate in 24-48 hoursProceed with surgical intervention nowIR guided drain placementCorrent answer: 4The patient is presenting with an acute hematogenous prosthetic joint infection, which requires surgical treatment as soon as safely possible.Periprosthetic joint infections (PJI) are generally managed surgically. Diagnosis is composed of a battery of findings as established by the Musculoskeletal Infection Society (MSIS), which requires the presence of one of two major criteria or four of six minor criteria (Illustration A). Acute infections can often be treated with irrigation and debridement with polyethylene exchange (IDPE), whereas chronic infections are best managed with a two-stage revision.Buller et al. performed a retrospective study looking at variable affecting the success of IDPE treatment for PJI. The authors found that infections with MRSA or VRE, higher ESR levels, symptoms longer than 3 weeks, and previous joint infections were strong risk factors for failure of IDPE. The authorsconcluded that patients presenting with these characteristics may be best treated with a two-stage revision rather than IDPE.Figures A and B are AP and lateral radiographs of a right knee with a stable appearing total knee arthroplasty prosthesis. Illustration A is a table that depicts the 2011 MSIS criteria for diagnosing prosthetic joint infections.Incorrect Answers:OrthoCash 2020A 63-year-old patient with a previous right TKA 4 years ago presents with worsening pain in the right knee. The patient reports that pain is worsened when starting physical activity, but is also present at night. Two weeks prior to presentation the patient was given a 1-week course of oral antibiotics for cellulitis affecting the right knee. Serum labs were significant for a CRP of 11 mg/L and an ESR of 35 mm/hr. Synovial fluid analysis revealed 1,000/µL nucleated cells with 85% PMNs and no evidence of crystals. Synovial cultures were negative for any bacterial or fungal growth. Synovial alpha-defensin is positive. Figures A and B are the AP and lateralradiographs of the right knee. The patient opts to undergo a revision total knee arthroplasty. What is the best management at this point?Femoral component revisionTibial component revisionPolyethylene component revisionOne-stage revision of both the femoral and tibial componentsTwo-stage revision of both the femoral and tibial componentsCorrent answer: 5The patient is presenting with increasing knee pain consistent with either septic or aseptic loosening of the prosthesis. Serum and synovial labs are not diagnostic for an infection, but there is a positive synovial alpha-defensin suggesting the presence of a chronic prosthetic joint infection.Prosthetic joint infections are diagnostic challenges as there is no single confirmatory test. Rather, diagnosis is composed of a conglomerate of physical and laboratory findings as laid forth by the Musculoskeletal Infection Society criteria. Diagnosis can be made by either the presence of one major criterion or four minor criteria. Synovial alpha-defensin is a new assay that tests for the presence of an antimicrobial peptide that is part of the innate immune system. Recent studies have suggested a high sensitivity and specificity of this test for prosthetic joint infections, even with prior antibiotic administration. Treatment involves two-stage revision arthroplasty with culture-specific antibiotics for at least six weeks. Reimplantation of a prosthesis is done with infection eradication is confirmed.Shahi et al. performed a retrospective diagnostic study looking at whether prior antibiotic administration affected synovial alpha-defensin levels. The authors found that alpha-defensin was not affected by prior antibiotic administration. The authors concluded that since many patients with PJI will present with prior antibiotic administration, alpha-defensin may be an ideal diagnostic adjunctive test.Frangiamore et al. performed a prospective cohort study on the sensitivity and specificity of alpha-defensins in diagnosing prosthetic joint infections. The authors found that alpha-defensin has a sensitivity and specificity of 100% and 98%, respectively, for diagnosing PJI in single-stage and first-stage revisions. The authors concluded that alpha-defensin has the potential as a useful adjunct in diagnosing PJI.Figures A and B demonstrate AP and lateral radiographs of the right knee with loosening of the tibial and femoral components. Illustration A depicts the MSIS criteria for the diagnosis of PJI.Incorrect Answers:OrthoCash 2020Of the following, which has the highest strength of recommendation according to the AAOS Clinical Practice Guidelines (CPG) for Surgical Management of Osteoarthritis of the Knee?Preoperative physical therapy improves pain and physical function postoperativelyTourniquet use during total knee arthroplasty (TKA) decreases short-term postoperative functionContinuous passive motion (CPM) after TKA improves outcomesRehabilitation started on the day of TKA reduces length of hospital staySurgical navigation should be used because there is a decrease in pain and functional outcomesRehabilitation started on the day of TKA decreasing length of stay has been deemed a "strong recommendation" by the AAOS.Postoperative management following TKA is an important aspect of achieving an optimal outcome following total knee arthroplasty. The general recommendation is that patients should work with a physical therapist on theday of surgery or as early as possible as it will decrease pain and improve function. Early rehabilitation is felt to also decrease the length of stay.Recommendations against cryotherapy machines and CPM are moderate and strong, respectively, as they do not appear to improve outcomes.McGrory et al. present the AAOS CPG's for surgical management of osteoarthritis of the knee. Strong evidence supports postoperative rehabilitation started on the day of surgery, which has been shown to decrease the length of stay. Moderate evidence supports rehabilitation starting the day of surgery compared to postoperative day 1 reduced pain and improves function. Various other preoperative and intraoperative topics are reviewed for the corresponding strength of recommendation.Incorrect Answers:OrthoCash 2020A 62-year-old patient that underwent a right hip resurfacing arthroplasty 3 years ago develops worsening right hip pain over the past 6 months. The pain is present at all times, including at night. The patient does not walk with a Trendelenburg gait and does not have reproducible pain on hip examination. Laboratory inflammatory markers from 1 week ago were erythrocyte sedimentation rate of 66 mm/hr (reference <20 mm/hr), C-reactive protein of 22 mg/dL (reference <2.5 mg/dL), cobalt 0.5 µg/L (reference <0.7 µg/L), and chromium of 0.4 µg/L (reference <0.4 µg/L). Figure A demonstrates an AP radiograph of the pelvis. What is the next best step in management?Physical therapyRoutine follow-upArthrocentesis with synovial fluid analysisstage revisionMetal artifact reduction sequence MRICorrent answer: 3The patient is presenting with a painful right hip after a metal-on-metal arthroplasty with recent elevated inflammatory markers and normal metal ion levels. The best next step in diagnostic workup would include an arthrocentesis with synovial fluid analysis.Diagnosis of chronic prosthetic joint infections is challenging due to the requirement of a conglomerate of physical and laboratory findings for the diagnosis. The most common presenting symptom is pain in the affected joint, but there may be draining sinus tracts and systemic inflammatory signs.Work-up should start with serum inflammatory markers, which if elevated should prompt an arthrocentesis with synovial fluid analysis. If the diagnosis is still not clear a repeat aspiration can be performed or frozen section performed in the operating room. It is important in aspiration of metal on metal joints to request manual cell counts as the metal debris can often result in faulty automated counts.Connelly et al. performed a prospective cohort study of indications for performing metal artifact reducing sequence (MARS) MRI on patients with metal-on-metal hip resurfacing arthroplasty. They found that elevated cobalt and chromium were the strongest predictors for an adverse local tissue reaction and using 1.15 ppb of Co and 1.09 ppb for chromium as cut-offs forperforming a MARS MRI.Yi et al. performed a retrospective study evaluating the diagnostic accuracy of serologic and synovial tests for PJI in MoM hip arthroplasty. The authors found that a high rate of inaccurate reporting of MoM aspirations, with 35% of inaccurate reports having a synovial WBC count >3000 suggesting a false positive for infection. The authors concluded that using synovial WBC >4350 and PMN >85% provided greater diagnostic sensitivity and specificity than standard MSIS criteria.Figure A demonstrates an AP pelvis radiograph with a stable appearing right hip resurfacing arthroplasty.Incorrect answers:OrthoCash 2020Compared to a cruciate retaining knee prosthesis, an anterior stabilized prosthesis has what effect on the contact area and what effect on the stability in PCL deficient knees?Decreased contact area; increased stabilityIncreased contact area; increased stabilityNo change in contact area; no change in stabilityDecreased contact area; decreased stabilityIncreased contact area; decreased stabilityCorrent answer: 2An anterior stabilized knee prosthesis is composed of highly conformed polyethylene component with a large anterior lip, which prevents anterior translation of the femur on the tibia. The high conformity of the polyethylene component increases the contact area of the implant.In arthroplasty, several factors can affect wear characteristics and stability at the bearing surface. Articular surfaces that are more congruous decrease the contact stresses at the surface by dispersing the joint reactive forces across a greater area. There are drawbacks to this as the articular surface is less anatomic and can prevent the natural roll back kinematics in total knee arthroplasty. New prosthesis designs with a large anterior lip formed on the bearing can be used to stabilize the knee in the absence of a functional PCL without sacrificing bone stock for the box cut and potential patellar complications.Peters et al. performed a retrospective cohort study of total knee arthroplasty outcomes between cruciate retaining prostheses in intact PCL knees and anterior stabilized bearing prostheses in PCL deficient knees. They found that anterior stabilized bearing prostheses had similar knee society scores, radiographic alignment, component loosening, and major complications but had a significantly lower number of revisions performed. They concluded that the use of anterior stabilized bearings is an effective implant to stabilize PCL deficient knees.Brockett et al. performed a biomechanical study that examined wear characteristics of poly-ether-ether-ketone (PEEK) and carbon fiber reinforced PEEK (CFR-PEEK) and compared to ultra-high molecular weight polyethylene (UHMWPE). It was found that PEEK had worse wear characteristics compared to UHMWPE, specifically with increasing contact pressures, decreased contact surface, and increased cross-shear. However, CFR-PEEK had similar wear performance as UHMWPE, but there were increased wear characteristics with increasing shear and contact pressure. They concluded that CFR-PEEK may be a potential alternative bearing surface in arthroplasty, but further investigation is needed to determine it's role in less conforming bearing due to the increased shearing wear.Illustration A depicts the design of a cruciate retaining total knee prosthesis and an anterior stabilized total knee prosthesis.Incorrect Answers:OrthoCash 2020Resection of the posterior cruciate ligament during total knee arthroplasty simulates which of the following techniques below?Excessive distal femur resectionExcessive distal femur augmentationExcessive posterior femur resectionExcessive posterior femur augmentationOversized femoral componentCorrent answer: 3Posterior cruciate ligament (PCL) resection during total knee arthroplasty (TKA) results in a relative increase in the flexion gap compared to the extension gap. This effect simulates excessive posterior femur resection, which also results in an increased flexion gap.The PCL acts as a central stabilizer to prevent posterior subluxation, allows femoral condyle roll back on the tibial plateau during flexion, and permits clearance of the tibia in high degrees of flexion to improve the mechanical efficiency of the extensor mechanism. The PCL may be preserved or resected during TKA. Biomechanical studies have demonstrated that after PCL resection, the flexion gap increases significantly compared with the extension gap. This has implications on gap balancing during posterior-stabilizing (PS) TKA, as the flexion gap must match the extension gap.Park et al. performed a study to investigate the change in the medial-lateral gap in flexion and extension after PCL resection in severely deformed knees and its effect on bone resection, rotation, and size of the femoral component. They reported that after PCL resection, the flexion gap increased significantly compared with the extension gap. They concluded that PCL resection in PS-TKA designs necessitates an increase in the size of the femoral component tobalance the resulting gap mismatch.Sierra et al. published an article on the surgical technique differences between cruciate-retaining (CR) and PS TKA designs. They reported that PCL resection selectively opens the flexion space approximately 2mm more than the extension space, resulting in some flexion instability. They recommended that in PS-TKA, surgeons must avoid flexion instability due to an extra large flexion space caused by PCL sacrifice and postoperative knee flexion contracture by underresection of the distal femur.Incorrect Answers:OrthoCash 2020A 70-year-old healthy woman presents with recurrent left prosthetic hip dislocations after undergoing total hip arthroplasty 6 months ago. Workup for infection has been negative. Radiographs from her visit today are depicted in Figure A. Which of the following will most definitively prevent further dislocations?Exchange polyethylene liner to a lipped acetabular linerExchange polyethylene liner to a thinner liner and increase the size of femoral head componentCemented acetabular component revisionUncemented acetabular component revisionExchange polyethylene liner to a constrained acetabular linerCorrent answer: 4This patient appears to have a significantly increased acetabular abduction (theta) angle, which places her at a high risk of periprosthetic dislocation. She should undergo revision of her malpositioned acetabular component to prevent further dislocation events.Variables that help determine stability after total hip arthroplasty (THA) include component design, component position, soft tissue tension, and soft tissue function. The component position comprises of both femoral and acetabular implants. The recommendations are femoral component anteversion of 10-15 degrees, acetabular anteversion of 5-25 degrees, and acetabular abduction of 30-50 degrees. Excessive abduction may result in posterosuperior instability whereas inadequate abduction may result in impingement during flexion as well as inferior instability. Component malposition generally requires revision and cannot be compensated for by abductor strengthening or orthoses.Dewal et al. retrospectively reviewed THA dislocations to determine the effectiveness of abduction bracing following closed reduction. They observed no significant differences in first-time dislocators or recurrent dislocators with or without the use of abduction braces. They concluded that abduction bracing following closed reduction of THA dislocation is ineffective in preventing re-dislocation.McCarthy et al. performed a study to investigate cup position angles associated with impingement in a group of subjects during different activities. They reported that true acetabular target for impingement-avoidance is much smaller than previously believed and varies considerably between patients and that certain tasks including low-chair rise and squatting decrease the size of the target zone. As such, they recommended preoperative patient-specific planning and intraoperative execution for placement of the components.Figure A depicts a THA construct with significantly increased acetabular abduction angle.Incorrect Answers:OrthoCash 2020A 65-year-old woman with a history of right total hip arthroplasty presents with a fall. Her injury radiographs are depicted in Figure A. What are the fracture classification and most appropriate treatment?Vancouver AG; nonoperative with partial weight bearingVancouver AG; open reduction internal fixation with trochanteric claw plateVancouver AG; femoral component revisionVancouver AL; open reduction internal fixation with trochanteric cablesVancouver B1; open reduction internal fixation with lateral locking plateCorrent answer: 2This patient has a displaced (> 2cm) greater trochanteric periprosthetic fracture around her previous right total hip arthroplasty (THA). Her fracture is classified in the Vancouver classification as AG, and is best treated with open reduction internal fixation (ORIF) using a trochanteric claw plate.The Vancouver hip periprosthetic classification system is one of the most useful classifications in the field of orthopaedic surgery, as it can reliably guide decision-making regarding fixation versus revision of the femoral component. Vancouver A fractures confer fractures about the femoral trochanters, with AG and AL fractures depicting greater and lesser trochanters, respectively. While nondisplaced and minimally displaced (<2cm) Vancouver AG fractures may be managed nonoperatively with protected weight-bearing, displaced AG fractures should be treated with ORIF using wires, cables, or claw plates.Sariyilmaz et al. performed a biomechanical study to compare fixation techniques (cables, trochanteric grip plates, and locking plates) in Vancouvertype AG periprosthetic femoral fractures. They reported that locking plate versus cable fixation and grip plate fixation versus cable fixation showed statistically significant superior results in axial distraction tests. They concluded that Vancouver type AG fractures may be treated with either grip plate fixation or locking plates, with the former ensuring more stable osteosynthesis.Masri et al. published a review article on the evaluation and management of periprosthetic fractures. They reported that the best outcome is achieved when the surgeon has a thorough understanding of the principles of treatment of periprosthetic fractures with access to various fixation and prosthetic devices. They concluded that the Vancouver classification offers a reproducible description of these factors and easily guides treatment.Figure A depicts a displaced greater trochanteric periprosthetic fracture. Illustration A depicts the Vancouver periprosthetic hip classification system. Illustration B depicts an example of a Vancouver AG fracture treated with ORIF using a claw plate.Incorrect Answers:OrthoCash 2020A 79-year-old man sustains a fall and presents with the injury depicted in Figures A and B. He underwent total knee arthroplasty (TKA) 5 days ago and had been doing well prior to his recent fall. What is the TKA implant design and what is the most appropriate treatment?Cruciate-retaining; Open reduction internal fixation with lateral locking plateCruciate-retaining; Retrograde femoral nailCruciate-retaining; Open reduction internal fixation with medial locking platePosterior-stabilized; Open reduction internal fixation with lateral locking platePosterior-stabilized; Femoral component revisionCorrent answer: 4The TKA prosthesis in question is a posterior-stabilized (PS) design. Open reduction and internal fixation (ORIF) with a lateral locking plate is a viable treatment option for a periprosthetic femur fracture around the femoral component of a well-fixed PS TKA.Femoral periprosthetic fractures after TKA may occur following low-energy trauma in osteopenic bone. Nondisplaced fractures with a stable prosthesis may be treated nonoperatively in a cast or brace. The decision for revision of the femoral component is guided by component stability versus loosening, with ORIF and revision arthroplasty indicated, respectively. ORIF options include locked femoral plating or retrograde intramedullary nailing (IMN).Retrograde IMN is not a viable option for stemmed femoral prosthesis and posterior-stabilized (PS) TKA systems without an open box design.Haidukewych et al. published an instructional course lecture on periprostheticfractures of the hip and knee. They reported internal fixation is indicated for the majority of periprosthetic distal femoral fractures. Both locked plates and retrograde IMNs can provide good outcomes, and that revision arthroplasty is indicated in fractures around loose components, nonunions, or fractures for which internal fixation attempts are likely to fail.Su et al. published a review on periprosthetic femoral fractures above total knee replacements. They reported that periprosthetic femoral fractures above TKAs can be managed by a variety of methods, including casting, ORIF, external fixation, or revision arthroplasty. They highlighted that classification based on fracture location helps guide treatment. They concluded that IMNs are best for proximal fractures, fixed-angle devices for fractures originating at the component, and revision arthroplasty for very distal fractures or those with component loosening.Figures A and B depict a periprosthetic femoral fracture originating at the anterior flange of the femoral component of a PS-TKA. Illustrations A and B depict radiographs of the periprosthetic femur fracture after ORIF with a lateral locking plate.Incorrect Answers:OrthoCash 2020A 67-year-old woman presents with chronic right hip pain, exacerbated by long walks. She has limited hip range of motion, particularly in flexion and internal rotation. Radiographs are depicted in Figure A. This is her first time seeking treatment. What is the mechanism of action of a medication strongly recommended for short-term pain relief according to the most recent (2013) AAOS Clinical Practice Guidelines?Direct action on hypothalamic regulating center with anti-pyretic effectsBinds to cannabinoid receptors in neural tissuesBinds directly to nuclear receptors to interrupt the inflammatory and immune cascade via mRNA changesMaintains synovial fluid viscosity and supports articular cartilage shock absorptionInhibits sodium ion channels to inhibit sensory nerve impulse initiation and conductionThis patient presents with right hip osteoarthritis. In the 2013 AAOS Clinical Practice Guidelines (CPG), intraarticular corticosteroids usage in improving function and pain reduction in the short-term for patients with symptomatic osteoarthritis of the hip was strongly recommended. Corticosteroids function by direct binding to nuclear steroid receptors to interrupt the inflammatory cascade through mRNA changes.The 2013 AAOS CPG for the treatment of symptomatic arthritis discuss both operative and non-operative treatment options and scrutinizes the literature for each modality. Amongst the strong recommendations are weight loss, low impact physical activity, and non-narcotic analgesia including nonsteroidal anti-inflammatory drugs (NSAIDs). Numerous modalities were not supported including the use of prescription opioids, acupuncture, needle lavage, hyaluronic acid, glucosamine and chondroitin, and arthroscopic lavage.Dieppe et al. published a review article on the management of hip osteoarthritis. They reported that shock absorbing shoe insoles and walking sticks can be of great benefit, while physiotherapy and hydrotherapy should be considered for more severe cases. They recommended simple analgesics such as paracetamol and NSAIDs as first-line treatment, with joint replacement considered in patients with severe pain or disability.Quinn et al. published a review article on the management of hip osteoarthritis using the AAOS Appropriate Use Criteria (AUC). Evidence-based information, in conjunction with the clinical expertise of physicians, was used to develop the criteria to improve patient care and obtain the best outcomes while considering the subtleties and distinctions necessary in making clinical decisions.Figure A depicts right hip osteoarthritis with evidence osteophytes, narrowed joint space, and subchondral sclerosis.Incorrect Answers:OrthoCash 2020A 70-year-old man presents with chronic persistent right knee pain and erythema which has been present for 7 weeks after having undergone total knee arthroplasty (TKA) 7 years ago. He is referred after completing a course of oral antibiotics prescribed by his primary care physician, which did not improve his symptoms. His current radiograph is shown in Figure A. Laboratory testing reveals a serum C-reactive protein (CRP) of 50mg/L and an erythrocyte sedimentation rate (ESR) of 67 mm/h. Arthrocentesis is performed and reveals a synovial WBC of 1,500 WBC/uL, with 85% polymorphonuclear cells (PMNs), and negative final cultures. The alpha-defensin test is positive. What is the next best step?Repeat knee arthrocentesis after 2-week antibiotic holidayRevision of femoral component without antibiotic therapyOne-stage revision arthroplasty with intravenous antibiotic therapy for 4-6 weeksTwo-stage revision arthroplasty with intravenous antibiotic therapy for 4-6 weeksRevision of tibial component without antibiotic therapyBased on the 2018 revised Musculoskeletal Infection Sociecty (MSIS) criteria, the elevated ESR, serum CRP, positive alpha defensin, and elevated PMNs convey a score of 1, 2, 3, and 2, respectively, for a combined score >6. This is diagnostic of a chronic prosthetic joint infection (PJI), for the most supported management strategy is two-stage revision arthroplasty with intravenous (IV) antibiotic therapy for 4-6 weeks.PJI after TKA is estimated to be 2.5%. The chronicity of the infection determines management. Non-MRSA PJI within 4 weeks of surgery is considered acute and may be treated with irrigation, debridement, polyethylene exchange, component retention, and IV antibiotics, as the organism has purportedly had too little time to form a robust biofilm. PJI occurring more than 4 weeks after TKA is considered chronic and, due to a high likelihood of biofilm formation, requires two-stage revision arthroplasty with IV antibiotic therapy.Ting et al. reviewed an algorithm-based approach for diagnosis of PJI. They reported that the diagnosis of PJI is made in 90% of patients by ESR and CRP, followed by arthrocentesis if the results are high, with a focus on synovial WBC count, differential, and cultures.Everhart et al. developed and validated a preoperative surgical site infection (SSI) risk score for primary or revision TKA and hip arthroplasty (THA). They reported that patient comorbidities composing the risk significantly influence SSI risk for primary or revision TKA and THA. They concluded that preoperative SSI risk can be objectively determined by the proposed SSI risk score.Parvizi et al. most recently presented the 2018 updated MSIS evidence-based criteria for diagnosis of periprosthetic hip and knee infections (Illustration A). The authors updated the original crtieria, expanding and refining the contributions from each of the minor criteria. The authors supported that a score >6 was diagnostic of periprosthetic infection. They concluded that this criteria was 97.7% sensitive and 99.5% specific for diagnosis of prosthetic joint infection.Figures and Illustrations:Figure A shows the AP and lateral radiographs of a TKA prosthesis with evidence of osteolysis and marked loosening of the femoral and tibial components.Illustration A is the updated 2018 MSIS criteria for diagnosis of a PJI.Incorrect Answers:OrthoCash 2020Figure A depicts the intraoperative findings during a revision total hip arthroplasty (THA) in a patient with chronic pain for the last two years after undergoing his index THA 10 years ago. Workup for infection was negative. The acetabular and femoral components are assessed to be well-fixed intraoperatively. Which of the following describes the best treatment option?Suppressive intravenous antibioticsTwo-stage revision arthroplastyIrrigation and debridementAcetabular component revisionRevision to new ceramic femoral head with titanium sleeveCorrent answer: 5This patient's symptoms and intraoperative image are consistent with trunnionosis. As the components appear well-fixed, the best treatment is a revision to a ceramic head with a titanium sleeve.Metal-on-metal (MoM) total hip arthroplasty (THA) has been associated with complications from metal debris and toxicity. Although morse taper technology allows machined taper trunnion to fit with the femoral head, complications have been reported including corrosion at the trunnion, which results in pain and is often associated with adverse local tissue reactions (ALTR). During revision surgery, a ceramic head with a titanium sleeve adaptor is advocated, as an exchange of the metal femoral head to another metal femoral head may result in recurrence of ALTR. Lastly, while no cutoffs for serum cobalt chromium ion levels have been identified as pathognomonic for trunnion corrosion, a serum cobalt level of 1.6 ng/mL (ppb) and greater has been suggested as a threshold for mechanically-assisted crevice corrosion.Weiser et al. published a current concepts review of trunnionosis in THA. They stated that the complication of trunnionosis in THA is likely underreported since it often causes concurrent osteolysis and loosening, which are more universally accepted diagnoses. They recommended analysis of serum cobalt and chromium ions as well as metal artifact reduction MRI during workup. In revision surgery, they advocated for head and liner exchange, with retentionof the acetabular and femoral components.Raju et al. published a case series on trunnionosis in metal-on-polyethylene (MoP)THA. They reported three failures (two dissociations of the femoral head from the neck), with the most likely contributing factors to failure being a large femoral head size, high horizontal offset, a low angled neck, and a titanium alloy taper with a cobalt-chromium head. They recommended high vigilance for any alteration of alignment between the femoral head and neck in follow-up radiographs after THA.Figure A is an intraoperative image depicting severe corrosion at the trunnion in a metal-on-metal THA.Incorrect Answers:OrthoCash 2020Figure A depicts the current radiograph of a 66-year-old man with significant right groin pain after undergoing right total hip arthroplasty (THA) 10 years ago. Revision surgery is planned after infection workup is negative. What is the classification of his diagnosis and what would the most appropriate treatment for the acetabulum?Paprosky I; cementless hemispheric cup with screw fixationPaprosky I; cemented hemispheric cup without screw fixationPaprosky IIB; cementless hemispheric cup with screw fixationPaprosky IIIA; cup/cage constructPaprosky IIIA; triflange reconstructionCorrent answer: 3This patient demonstrates superior acetabular rim loss and superolateral migration that can be characterized as Paprosky IIB in the Paprosky classification for acetabular bone loss. This may be managed with a hemispheric acetabular cup with screw fixation.Acetabular bone loss poses a technical challenge in THA. The Paprosky classification for acetabular bone loss helps guide treatment for revision THA. Broadly speaking, Paprosky Type I and II defects may be managed with a porous-coated hemisphere cup secured with screws, and Type III defects managed with reconstruction cages protected with cups, structural augments, or custom triflange implants.Sheth et al. published a review article on the evaluation and management of acetabular bone loss in revision THA. They reported that appropriate radiographs are key in quantifying acetabular bone loss, and specific classification schemes can assist in identifying bone loss patterns which guide available treatment options. They concluded that depending on the severity of bone loss, treatment may include impaction grafting and acetabular cementation, cementless hemispheric acetabular reconstruction, structural allograft reconstruction, cementless reconstruction with modular porous metalaugments, ring and cage reconstruction, cup-cage reconstruction, and triflange reconstruction.Paprosky et al. performed a 6-year follow up evaluation study on acetabular defect classification and surgical reconstruction in revision THA. They typed acetabular defects from 1 to 3 and reconstructed with bulk or support allograft depending on the type. They concluded that the size, orientation, and method of fixation of the allografts utilized during revision THA play a pivotal role in the integrity of structural allografts, and stressed the importance of adequate host-bone to ensure solid bone ingrowth.Dennis et al. published on the outcomes after Paprosky Type III acetabular bone loss reconstructed using custom triflanged acetabular components. They reported stable fixation and reconstruction of periacetabular bone in over 80% of patients at short-term follow up. They recommended that this technique be used with caution in cases of preoperative hemipelvis dissociation unless additional column plating is performed.Figure A demonstrates Paprosky IIB acetabular bone loss with superolateral migration of the acetabular component. Illustration A depicts the Paprosky classification.Incorrect Answers:OrthoCash 2020A 72-year-old male presents with worsening left hip pain 12 years after total hip arthroplasty. On examination, the patient has a Trendelenburg gait with a 3.5 cm leg length discrepancy. The patient denies any fevers or chills. Current radiographs are shown in figure A. Recent ESR and CRP are 21 mm/hr and 1.2 mg/L, respectively. What is the preferred treatment option to address these findings?Large porous hemispheric cup with particulate bone graft and augmented with screw fixationCustom triflanged acetabular componentCemented large porous hemispheric cupMetal augments with large porous hemispheric cup and bone grafting combined with screw augmentationstage revision arthroplastyCorrent answer: 4The patient is presenting with a Paprosky type IIIA acetabular defect with the migration of the hip center in a superolateral direction. The preferred treatment option would be to provide structural stability of the cup with metal augments combined with bone grafting and cement reinforcement and screw fixation.Acetabular bone loss can make revision total hip arthroplasty challenging due to lack of structural support of the acetabular cup as well as concerns for bony ingrowth potentially compromising implant longevity. The Paprosky classification was designed to identify the location and degree of acetabular bone loss and thereby to guide treatment of the respective defects. In type IIIA defects there is bone loss of the superolateral acetabulum with greater than 3 cm migration of the center of the femoral head, also described as "up and out." Intraoperatively structural support must be reestablished for the revision cup by either structural allograft or metal augments. Further bone grafting is performed to enhance long term bone ingrowth of the prosthesis.Sheth et al. performed a literature review on the evaluation and management of acetabular bone loss in revision total hip arthroplasty. The authors reviewed the Paprosky classification for acetabular bone loss and recommended the use of noncemented, porous-coated, hemispheric cups with adjunctive screw fixation in type I, IIA, and IIB defects. For type IIC defects, the authors recommended highly porous, noncemented, hemispheric cups with screw fixation and bone grafting of the medial wall defect. For type IIIA defects, they advocated for the use of metal augments or structural allograft combined with porous hemispheric cups and augmentation with screw fixation and cement.Lastly, for type IIIB defects, they recommended the use of noncemented acetabular devices combined with structural allograft, structural augments, and a reconstruction cage.Paprosky et al. performed a retrospective study of patients undergoing revision total hip arthroplasty and proposed a classification system of acetabular bone loss, recommending treatment options for each type. The authors found that of the 147 implants included in the study, only 6 required repeat revision, all of which were type IIIB defects. The authors concluded that adherence to this classification system and the recommended reconstruction techniques can produce acceptable and predictable results in acetabular revision surgery.Dennis et al. performed a retrospective review of twenty-four patients with Paprosky type IIIB acetabular defects treated with a custom triflanged acetabular component (CTAC). The authors found that of the twenty-four patients treated, three (87.5%) were considered to have radiographic and clinical signs of failure, with one requiring resection arthroplasty. There were two hip dislocations necessitating only closed reduction. The authors concluded that CTAC is an effective means to treat type IIIB acetabular defects, but should be used with caution in cases of pelvic discontinuity unless additional column plating performed.Figure A is the AP radiograph of a pelvis with a Paprosky type IIIA acetabular defect. Illustration A is the post-op radiograph after reconstruction with metal augments and large porous hemispheric cup. Illustration B is a table with the description of the Paprosky classification. Illustration C is a diagram depicting the Paprosky classification.Incorrect Answers:OrthoCash 2020A 67-year-old woman with poliomyelitis presents with quadriceps weakness and chronic right knee pain for the last 2 years. She is scheduled to undergo right total knee arthroplasty (TKA) after failing nonoperative modalities. Her preoperative radiographs are shown in Figures A and B. What technique should be utilized to optimize her function and to prevent the recurrence of her deformity?Posterior stabilized design with under-resection of distal femurPosterior stabilized design with under-resection of proximal tibiaPosterior stabilized design with under-resection of posterior femurVarus-valgus constrained designRotating hinge designThis patient with neuromuscular disease has genu valgum with recurvatum (hyperextension). Of the techniques listed above, utilization of a rotating hinge TKA design would most likely optimize her function and prevent recurrence of her recurvatum deformity because of the implant’s extension stop.Genu recurvatum is associated with deformities such as genu valgum, ligamentous laxity, and neuromuscular diseases, which are often accompanied by equinus ankle contractures. Knee hyperextension is likely to recur after TKA in patients with neuromuscular disorders such as poliomyelitis due to the bony deformity, muscle weakness, and paralysis seen in these patients. Several strategies to correct knee hyperextension at the time of primary TKA have been described and include posterior capsular plication, proximal and posterior transfer of collateral ligaments, under-resection of distal femur and proximal tibia, and the use of thicker components. In severe cases where ligament integrity is likely compromised, utilization of more constrained prostheses is recommended.Giori et al. performed a retrospective study of patients with poliomyelitis involving a limb that underwent primary TKA. Complications reported included two periprosthetic fractures, one peroneal nerve palsy, one patellar tendon avulsion, and four cases of recurrent instability, all attributable to the poor bone quality, valgus deformity, patella baja, poor musculature, and attenuated soft tissues observed in knees with poliomyelitis. They concluded that pain and knee scores improved following TKA this cohort of patients and recurrence of instability and progressive functional deterioration is possible postoperatively.Paratte et al. published an AAOS Instructional Course Lecture on instability after TKA. They reported knee hyperextension before TKA is seen in <1% of patients and is most commonly seen in patients with neuromuscular disease like poliomyelitis. They recommended solutions to be considered for such patients such as distal femur under-resection, distal femoral augmentation blocks with the knee left with a slight flexion contracture, translation of the femoral origins of the medial collateral ligament and lateral collateral ligaments proximally and posteriorly to recreate the normal tightening action during full extension of the knee, and the use of a rotating-hinge total knee prosthesis with an extension stop.Meding et al. published a review article on the etiology and surgical treatment of genu recurvatum during TKA. They emphasized the importance of diagnosing and elucidating the etiology of the hyperextension deformity prior to surgery since the deformity is known to recur in patients with certain neuromuscular disorders. They recommended a meticulous approach andavoiding even mild degrees of residual instability in the coronal plane at surgery since this is associated with increased extension in the postoperative period.Figures A and B depict severe right knee osteoarthritis with valgus and recurvatum deformities. Illustration A depicts a rotating-hinge TKA prosthesis.Incorrect Answers:OrthoCash 2020A 57-year-old man with a history of chronic lower back pain and right hip arthritis is postoperative day 2 from an uncomplicated right total hip arthroplasty with a spinal block. Since the procedure, he has reported persistent pain in his right leg with a focal point in the proximal lateral leg. He has had difficulty getting out of bed for physical therapy due to pain reproduced in his leg. He is voiding but has not yet had a bowel movement. Physical exam is only significant for decreased ankle dorsiflexion strength on the right. Plantarflexion strength remains 5/5 bilaterally. No point tenderness was elicited and Homan's sign is negative. His wound is unremarkable with typical post-operative swelling of the leg and no significant drainage. He hasbeen receiving ASA 81mg PO daily since surgery and has been wearing compression stockings full-time. Postoperative repeat radiographs of the hip are unremarkable and his hemoglobin is stable. Which of thefollowing etiologies is most likely responsible for this patient's symptoms?Residual effect of the spinal blockLumbar lateral recess stenosisGluteal hematomaAcute post-operative infectionVenous thomboembolismDuring total hip arthroplasty, a "double crush" injury can occur to the sciatic nerve in the presence of pre-existing degenerative lumbar spondylosis, leading to persistent pain and post-operative motor weakness. The best study would be a lumbar MRI to evaluate for lumbar spinal stenosis.Nerve injuries following total hip arthroplasty are rare and usually affect the sciatic nerve. The peroneal branch appears to be the most commonly affected due to its more superficial and lateral position, more the tightly packed fascicles, and greater adherence to the surrounding tissues compared to the tibial division. Lumbar degenerative disc disease commonly occurs in the presence of coxarthrosis, with spinal stenosis being exacerbated by traction neurapraxia during the procedure.DeHart et al. reviewed nerve injuries and postoperative management. The authors stated that the sciatic nerve is the most commonly injured nerve, with up to 70% of cases have subclinical electrodiagnostic changes. The cause of this is multifactorial, but the vast majority of studies reviewed reported complete spontaneous recovery by 6-12 months. The authors recommend observation of the nerve deficit with ankle-foot-orthosis and follow-up EMG to determine the level of the injury.Pritchett performed a review of 21 patients that presented with a foot drop after total hip arthroplasty. All patients reported prior back and leg pain prior to the procedure, with post-op MRI demonstrating severe spinal stenosis. The author postulated there to be a double crush phenomenon, with patients undergoing lumbar laminectomy having improvement or complete resolution. The author concluded that select patients presenting with foot drop following THA may benefit from a lumbar laminectomy.Incorrect Answers:and paresthesias are uncommon after a spinal block but have been reported with regional anesthesia, such as a sciatic nerve block. Furthermore a spinal would be unlikely to have any residual effect still post-operative day 2.OrthoCash 2020A 65-year-old female presents to the clinic with isolated medial-sided left knee pain. She has since exhausted conservative management but remains persistently symptomatic. The physical exam and radiographic work-up demonstrates isolated medial tibiofemoral compartment involvement. After discussion of the surgical options, she undergoes the procedure shown in Figure A. She initially does well but returns to clinic 3 months post-operatively with significantly increased medial-sided knee pain and the injury shown in Figure B. All of the following technical errors likely contributed to this complication EXCEPT?Excessive force impacting the tibial componentPenetration of the posterior tibial cortex with proximal guide pinPlacement of a peripheral medial cortical guide pinTibial resection guide replacement with re-drilling of the two proximal guide holesUnder-sizing of the tibial componentCorrent answer: 1The patient presents with a periprosthetic tibial stress fracture following a medial unicompartmental knee arthroplasty. Excessive force used when impacting the tibial component could potentially lead to intra-operative fracture, but this would be recognized in the acute post-operative period.With continuing advances in surgical technique, UKA has demonstrated increasingly promising midterm outcomes. However, there are number of technical considerations that directly impact survivorship and the potential for post-operative complications. While aseptic loosening remains the most common mode of early failure necessitating conversion to TKA, literature is replete with reports of early failure secondary to proximal tibia stress fractures. Stress fractures have been linked to a number of largely non-modifiable patient characteristics to include bone quality, but technical errors remain a controllable contributing factor. Recent studies have found that excessive guide pin number and suboptimal placement for the tibial resection guide as well as tibial component undersizing are associated with increased proximal tibial mechanical stress and may result in fracture.Brumby et al. described a series of tibial plateau stress fractures subsequent to UKA. The authors attributed these to mechanical weakening of the proximal tibia from the guide pin and lug holes drilled for the guide and tibial component, respectively. They noted that this even occurred in some cases with penetration of the medial tibial cortex by a single pin. Stress fractures presented at a median of 8 weeks post-operatively and in all cases required revision to TKA. They recommended post-operative monitoring of patients in whom a guide with 3 or more pins was utilized, or with any peripheral pins that breach the medial tibial cortex.Vince et al. present a review of the evolution, indications, and outcomes following UKA. The authors specifically highlight guide pin holes as a major contributing factor to periprosthetic fractures. They recommend limiting the number of holes drilled for placement of the tibial resection guides and paying careful attention to placement, specifically with regard to violation of the medial cortex. Furthermore, the authors advocated that a single proximal pin, placed centrally, and the guide secured distally by the ankle clamp would besufficient for stability and alignment while avoiding increased stress on the proximal tibia.Figure A is an AP weight-bearing radiograph of the left knee demonstrating isolated medial tibiofemoral arthritis.Figure B is a post-operative radiograph of the left knee significant for a medial UKA. Figure C is a follow-up AP radiograph of the left knee demonstrating a periprosthetic fracture involving the medial UKA with significant varus collapse.Incorrect answers:OrthoCash 2020A 65-year-old male presents to your clinic for evaluation of right hip pain. He underwent a right total hip arthroplasty (THA) 20 years prior and was doing very well until 2 years ago. He admits to groin pain when getting up from a seated position. He denies any fevers or chills. Radiograph is shown in Figure A. Which of the following would preclude the patient from undergoing a single-stage surgical intervention without further workup?Elevated serum cobaltMetallosis noted intra-operativelySignificantly higher serum cobalt then serum chrome levelsElevated ESR and CRPPseudotumor noted on MRICorrent answer: 4An elevated ESR and CRP are screening labs used to determine if further workup is required to rule out a periprosthetic joint infection (PJI). A patient with an elevated ESR and CRP should thus undergo further workup including a joint aspiration prior to consideration of a single-stage revision THA.The differential diagnosis of pain after THA encompasses a number of etiologies. While radiographs may point to loosening of the stem or the cup, osteolysis or a stress fracture, the first step in management needs to evaluate for a PJI. Accordingly, ESR and CRP are logical next screening steps in the workup. If elevated, additional studies need to be obtained such as joint aspiration with manual diff (to look for elevated synovial WBC, synovial PMNs or a positive culture), immunoassays (alpha-defensive, leukocyte esterase colorimetric strip) and serum IL-6. If the additional workup for infection is negative, it is safe to proceed with a single-stage revision THA. Metal on metal THA have their own set of modes of failure leading to bony erosion and pain.The majority of these are aseptic and allow for a single-stage revision including metallosis, pseudotumor, and metal hypersensitivity.Parvizi et al. performed a retrospective cohort study to examine the effectiveness of surgical treatment in treating hip and knee PJI caused by MRSA. They looked at 127 patients with a minimum of 2 years follow-up or until recurrence of PJI. In 35 patients, only an I&D with prosthetic retention was performed while a 2 stage explantation and reimplantation was performed in the other 92 patients. Of those who underwent an I&D and implant retention, only 37% of cases had successful eradication of the infectionwhereas two-stage exchange arthroplasty controlled the infection in 75% of hips and 60% of knees in the other 92 patients. Furthermore, cardiac disease was associated with a higher likelihood of failure to control infection in all treatment groups.Shukla et al. evaluated 87 hips with a PJI that were treated with explantation, antibiotic spacer and 6 weeks of antibiotics. The authors looked at ESR and CRP before reimplantation and obtained synovial WBC at the time of reimplantation. The authors noted 9 hips (10.1%) had persistent infections at the time of re-implantation. The mean ESR, CRP, and synovial fluid WBC count had significantly decreased between stages; however, the ESR remained elevated in 50 patients (62.5%) and the CRP remained elevated in 22 patients (27.5%) in whom the infection had been eradicated. The authors noted that the synovial fluid WBC count was the best test for identifying persistent infection, with an optimum cutoff of 3528 WBCs/microL (sensitivity, 78%; specificity, 96%).Browne et al. evaluated 37 patients with metal on metal THA or resurfacing arthroplasties who underwent revision to determine the clinical, radiographic, laboratory, intraoperative, and histopathologic findings to determine the cause of failure. Of the 37 patients, 10 were revised due to metal on metal hypersensitivity, 8 due to chronic inflammation with lymphocytic infiltration, 8 with aseptic loosening, 2 with iliopsoas impingement, 3 with femoral neck fracture after resurfacing arthroplasty and 6 due to infection, instability, and periprosthetic fracture. The authors stressed increased awareness of the wide variety of modes of failure associated with metal-on-metal articulations.Figure A is an AP pelvis showing a characteristic appearance of a metal-on-metal THA with a large femoral head.Incorrect Answers:OrthoCash 2020The use of a high-offset femoral stem leads to which of the following changes with regard to total hip arthroplasty?Increased joint reactive forcesIncreased leg lengthIncreased risk of acetabular component looseningIncreased soft tissue tensionA higher rate of dislocationCorrent answer: 4A high-offset femoral stem leads to increased soft tissue tension without affecting leg length.Femoral offset is defined as the distance from the femoral head center of rotation to the center of the long axis of the femur. Restoration of offset improves overall arthroplasty biomechanics with decreased cup strain and polyethylene wear, decreased dislocation risk, increased hip abductor strength, and lower rates of postoperative limp. The drawback of too much femoral offset is an increased risk of lateral prominence and subsequent trochanteric bursitis.Lecerf et al. reviewed the femoral offset with regard to total hip arthroplasty. They state femoral offset does correlate closely with the hip abductor lever arm and hip abductor strength. They conclude that femoral offset is important for improved hip function and longevity after total hip arthroplasty.Flecher et al. reviewed limb lengthening as it pertains to total hip arthroplasty. They discuss methods of assessing limb length including EOS and CT imaging as well as intraoperative robotic or computer assistance. They comment that the expectations of limb function after total hip make it crucial for surgeons to understand the three-dimensional geometry and placement of prostheses.Illustration A shows an example of a standard and high offset stem and how it maintains leg length while increasing offset.Incorrect Answers:OrthoCash 2020You are currently evaluating a 68-year-old woman who has met indications for a total knee arthroplasty. You finally have finished documenting the patient’s extensively detailed social and family history. As you finish, the patient tells you that she has spoken with her friends regarding her knee and tells you that she wants a prescription for preoperative physical therapy, would like a drain placed, an order for a cryotherapy device and use of a patient-controlled analgesia (PCA), in addition to being mobilized with physical therapy on the day of surgery. As an astute resident you inform the patient that based on the current AAOS clinical practice guidelines (CPG), there is strong evidence against using which of the patient’s request?Preoperative physical therapyDrain placementCryotherapy devicePostoperative day 0 mobilizationPatient-controlled analgesiaBased on the most recently published AAOS CPG, there is strong evidence to support not using a drain with total knee arthroplasty (TKA) because there is not any difference in complications or outcomes.The use of a drain was postulated to aid in decreasing postoperative infection, swelling, blood transfusions, hematoma formation, pain, length of hospital stay, and re-operation rates. In addition, their use was meant to improvepostoperative range of motion. However, after review of the high- and moderate-quality studies and with input from the multiple orthopaedic and medical societies, there has not been any clear advantage to the use of drains after unilateral total knee arthroplasty when comparing complication profiles and outcomes.McGrory et al. published a systematic review on the surgical management of osteoarthritis of the knee. In an effort to improve the surgical management of patients with osteoarthritis, the authors provide 38 evidence-based recommendations on topics specific to the preoperative, perioperative and postoperative treatment of such patients. Additionally, each topic was further classified based on the level of evidence available (limited, moderate, and strong) to support or not support a give recommendation.MacDonald et al. completed a prospective randomized clinical trial using continuous passive motion (CPM) following TKA. The patients were separated into two separate treatment groups plus a control group. The patients were followed over the course of one year from surgery. Similar to postoperative drain placement following TKA, MacDonald et al. were unable to demonstrate any significant difference in outcomes for CPM versus no CPM.Incorrect Answers:OrthoCash 2020Figure A is the radiograph of a male who fell down the stairs. He is 8 years status post right total hip arthroplasty. All of the following are indications for a proximal femoral replacement EXCEPT?<4cm of diaphyseal cortical boneAge <50 yearsExtensive metadiaphyseal proximal bone loss with <4cm of intact isthmic boneNonunion of the proximal femur with multiple failed attempts at osteosynthesisPaprosky IV femoral bone lossCorrent answer: 2The radiograph demonstrates a Paprosky type IV femoral deficiency. Given the substantial bone loss with limited proximal femoral support, a proximal femoral replacement is recommended.Postoperative fractures around a total hip prosthesis has an incidence of 0.1% and occurs most commonly at the tip of the stem. Proximal femoral support is important to evaluate following a periprosthetic fracture of the hip. The Paprosky classification of femoral bone loss helps guide treatment. A Paprosky type IIIb or IV femoral deficiency would benefit from either an allograft prosthetic component or a megaprosthesis/modular oncology component.Additionally, impaction bone grafting is indicated with a large canal and thin cortices for Paprosky IIIb and IV defects. Revising the femur to a proximalfemoral replacement would allow early mobility and provide better fixation, given the substantial bone loss for proximal support and is typically reserved for the elderly or sedentary patient.Parvizi et al. review the use of a proximal femoral replacement (megaprosthesis) in revision hip surgery. They report that with the increased use of cortical strut grafts to augment host bone, the indications for the use of megaprostheses have narrowed. They conclude that currently, the use of megaprostheses is reserved for elderly or sedentary patients with massive proximal femoral bone loss that cannot be reconstructed by other reconstructive procedures.Brown et al. tests the inter-observer and intra-observer reliability of this Paprosky classification of femoral bone loss. They report an inter-observer reliability of 0.61, indicating substantial agreement between surgeons. They also show a high intra-observer reliability, indicating substantial to almost perfect agreement. They conclude that there is substantial agreement among experienced arthroplasty surgeons when using the Paprosky Classification to characterize femoral bone loss.Figure A is the AP radiograph of the right hip which demonstrates a Paprosky type IV femoral deficiency. Illustration A is the Paprosky classification of proximal femoral bone loss.Incorrect Answers:OrthoCash 2020A healthy, active, 65-year-old male underwent a total knee arthroplasty 1 year ago. He presents to the emergency room after a ground-level fall earlier in the day. On exam, the patient is unable to perform a straight leg raise. Figure A is his current lateral radiograph. What is the most appropriate treatment for this patient?Immediate active and passive range of motion in a hinged braceImmobilization for 2 weeks followed by aggressive physical therapyCylinder cast for 6 weeksOpen Reduction Internal FixationPartial patellectomyThis patient has a displaced patella fracture with a disrupted extensor mechanism; therefore, (4) open reduction internal fixation is the correct answer.Risk factors for patella fracture following total knee arthroplasty include trauma, the performance of a lateral release, damage to the blood supply, and excessive resection at the time of resurfacing. Indication for non-operative management includes both implant stability and extensor mechanism competency. If the implant is unstable or the extensor mechanism is disrupted a variety of surgical options exist including open reduction internal fixation (ORIF), component revision, partial or complete patellectomy or extensor mechanism allograft.Konan et al. reviewed the management of periprosthetic total knee fractures. They report that non-operative treatment for periprosthetic patella fractures with an intact extensor mechanism leads to better outcomes when compared to surgery. Surgery is associated with high complication rates, including infection and nonunion. They conclude that regardless of the treatment employed, the goal should be early patient mobilization.Kuyzk et al. reviewed the management of periprosthetic total knee fractures. They note that periprosthetic patella fractures are the least common type of fracture in this population. Their review concludes that host bone stock is one of the most important factors when determining the revision implant type.Figure A demonstrates a displaced patella fracture in a patient with a previous total knee arthroplasty.Incorrect answersOrthoCash 2020A 91-year-old, minimally ambulatory male presents with acute on chronic progressive right thigh pain. Fifteen years ago, he underwent a right total hip replacement and he had been having progressive thigh start-up pain over the prior 5 months. He sustained a ground-level fall yesterday and he is now unable to bear any weight on the right leg. His current radiograph is shown in Figure A. His labs, including CBC, ESR, and CRP are all within normal limits. Which of the following represents the most appropriate next step in definitive management?Revision to a proximal femoral replacementOpen reduction and internal fixation with proximal femoral locking plate and cerclage cablesRevision to a cemented long femoral stemOpen reduction and internal fixation with iliac crest bone graftingRevision to a cementless long porous-coated femoral stemCorrent answer: 1The patient has a Vancouver B3 periprosthetic femur fracture and requires revision. Given the extensive amount of bone loss in the proximal segment as well as a loose stem, a proximal femoral replacement would be an appropriate treatmentPost-operative periprosthetic femur fractures are classified based on the Vancouver classification which classifies fractures based on the location of the fracture, implant stability, and bone loss. Vancouver B3 periprosthetic femur fractures are defined as fractures at, around, or just below the stem with significant proximal bone loss/osteopenia or comminution which is unable to allow for reconstruction. In the setting of these injuries, treatment would consist of endoprosthetic proximal femur replacement or replacement with a large proximal femur allograft.Della Valle et al. discuss the challenges associated with pre-operative planning for femoral revision total hip arthroplasty. The authors provide a classification of femoral bone loss that guides the surgeon in selecting an appropriate method of reconstruction. They conclude that appropriate pre-operative planning is required for the management of femoral implant revision in the setting of fracture, osteolysis, and instability.Brown et al. reviewed the indications for revision THA to include instability, aseptic loosening, osteolysis, infection, periprosthetic fracture, component malposition, and catastrophic implant failure. They note that femoral component revision presents a complex challenge to the arthroplasty surgeon because of modern implant design as well as bone loss in the proximal femur. They conclude that knowledge of various reconstructive options and the indications for each is necessary to achieve a successful outcome.Figure A is the radiograph of a periprosthetic femur fracture with extensive proximal femoral bone loss consistent with a Vancouver B3 periprosthetic femur fracture. Illustrations A and B are the radiographs revealing a revision total hip arthroplasty with proximal femur endoprosthetic reconstruction.Incorrect Answers:OrthoCash 2020A 64-year-old male is 6 months out from left total knee arthroplasty. He has had at least two months of pain and swelling to the operative joint. In your initial workup, he is found to have a well-healed surgical incision, a serum CRP of 13mg/L and an ESR of 19mm/h. You perform arthrocentesis, which results in a negative alpha-defensin, synovial WBC of 1000 cells/µL, synovial PMNs of 90%, and synovial CRP of 4mg/L. What is the next best step in management?Corticosteroid injectionProceed to OR for histologic examinationProceed with two stage revisionProceed with single stage polyethylene exchange with irrigation and debridement6 weeks of IV antibioticsThe patient has a score of 4 (2 points for elevated serum CRP, 2 points for elevated synovial PMN %) according to Parvizi et al's "The 2018 Definition of Periprosthetic Hip and Knee Infection: An Evidence-Based and Validated Criteria". This results in an ‘inconclusive’ determination of whether the patient has a periprosthetic joint infection. The best next step is to proceed to the OR in order to obtain tissue for histologic examination, cultures, and to determine whether purulence is present.Periprosthetic joint infections can be devastating. Chronic PJI of the hip and knee is typically treated with two-stage revision arthroplasty. The first stage involves removal of the orthopaedic implants, placement of an antibiotic spacer, and at least 6 weeks of intravenous antibiotics. Once there is evidence that the infection has cleared (i.e. serum and synovial analysis), the second stage involves removal of the antibiotic spacer and placement of revision components.Parvizi et al. updated their definition of PJI in 2018. They kept the major criteria for a chronic periprosthetic joint infection the same (an infection is indicated when 2 positive cultures of the same organism are isolated, or a sinus tract is present), but made several changes to the minor criteria.Namely, they assign a point criteria in which a score of ≥6 is reliably infected, 2-5 is inconclusive, and 0-1 is not infected. In the case of infection, their recommendation is to proceed with a two-stage revision. If an inconclusive score is met, the recommendation is to proceed to the OR for histologic examination, cultures, and to determine whether purulence is present. The update to the MSIS criteria provides a sensitivity of 97.7% and a specificity of 99.5%.Parvizi et al. reviewed 54 consecutive THA two-stage revisions. In their review, they determined MRSA to be the most common causative organism: MRSA 27.7%, S.epidermidis 18.4%, followed by MSSA 14.8%. They followed patients for a mean of 32 months, during which 26% had a recurrent infection and 8% developed mechanical failure (loose acetabular or femoral components).Della Valle et al. made 15 CPGs (clinical practice guidelines) in JAAOS 2010. Among their recommendations: 1) they recommended utilizing serum CRP and ESR in assessing for PJI, 2) they recommended aspiration if serum CRP/ESR are abnormal, 3) if the initial aspiration has unexpected results they recommend repeat aspiration, and 4) 2 week antibiotic holiday before attaining cultures.Illustration A shows the scoring criteria for the 2018 PJI update.Incorrect Answers:OrthoCash 2020A 66-year-old male is undergoing a total knee arthroplasty using a fixed bearing posterior stabilized component. During the intraoperative trialing of the components, it is noted that the flexion gap is loose, and the extension gap is appropriate. Compared to a patient with appropriate flexion and extension gaps, this patient would be at an increased risk for which of the following?Manipulation under anesthesiaKnee hyperextensionPosterior knee dislocationAnterior knee dislocationPatella fractureA loose flexion gap in a posterior stabilized primary total knee arthroplasty can lead to an atraumatic posterior knee dislocation during knee flexion.A posteriorly stabilized knee has a post built into the polyethylene bearing that articulates with the box of the femoral component in flexion to act as a cam mechanism. It is felt to occur when the patient is in moderate to deep flexion and tibia is able to translate posteriorly. The post becomes locked behind the cam and the patient is unable to extend the knee. The etiology is felt to be related to implant design, soft tissue laxity over time, and surgeon technique.Clarke et al. review flexion instability as a mode of failure in knee replacements. They describe how this is usually due to a lack of adequate balance at the time of surgery. They also report that revision surgery is usually the only way to correct symptomatic flexion instability.Lombardi et al. reviewed 15 cases of dislocation in three different implant designs given the statistically significant difference in the rate of dislocation. They found the only significant difference between the group of patients with dislocation was increased flexion. They state the majority of the dislocations occurred prior to a modification in the tibial polyethylene insert of the specific knee design they studied.Illustration A shows an example of a posteriorly dislocated total knee arthroplasty following a "jumped post" dislocation.Incorrect Answers:OrthoCash 2020A 78-year-old woman who has a history of an uncomplicated right total hip arthroplasty presents after a fall. Figure A is the radiograph obtained in the emergency department. What is the most appropriate treatment for the femoral component?Retained femoral stem with open reduction internal fixationRevision femoral stem to an uncemented long stem with strut allograftRevision femoral stem to a cemented long stem with open reduction internal fixationRevision femoral stem to an uncemented long stem with open reduction internal fixationProximal femoral replacementCorrent answer: 4In this scenario, the stem is loose with good proximal bone stock. The best option would be revision femoral stem to an uncemented long stem with an open reduction of the fracture.Operative treatment of periprosthetic fractures is directed by the location of the fracture, the stability of the implant, and remaining bone stock. In circumstances where the femoral implant has loosened or subsided revision to a long stem is recommended. Cemented fixation is less ideal in a fracture scenario given cement interference with fracture healing. After bypassing the fracture with a long stem the fracture is reduced and stabilized to provide an environment for healing and long term durability.Ko et al. reviewed 14 patients who underwent revision to a Wagner stemfollowing a B2 periprosthetic fracture. They found all 12 patients who followed up went on to union with 10 achieving good or excellent outcomes. They concluded the Wagner revision stem is a satisfactory prosthesis for Vancouver B2 periprosthetic femur fractures.Kwong et al. reviewed 143 patients who underwent revision total hip for a proximally compromised femur to a modular cementless femoral stem.Roughly ~10% of these patients were revised for periprosthetic fracture. They found a 97.2% survival rate and an average Harris hip score of 92. They concluded that the modular cementless diaphyseal engaging revision stem allows for adequate revisions THA for the proximally compromised femur.Figure A shows a loose femoral component with subsidence and a periprosthetic fracture. Illustration A shows an AP of the right hip following open reduction internal fixation as well as a revision to an uncemented long stem and revision of the acetabular components.Incorrect Answers:OrthoCash 2020A 78-year-old female with end-stage arthritis of the left hip is schedule for a total hip arthroplasty. Her contralateral hip was replaced 4 years prior and a current radiograph is shown in Figure A. Which of the following would be the most effective at preventing the complication shown in the Figure?Indomethacin treatment for 2 days postoperativelyLeaving 2 drains in place until at least 4 days post-operativelyPostoperative administration of ethylhydroxydiphosphonatePreoperative administration of radiation therapy 1 week before surgeryPostoperative administration of radiation therapy 8 hours following the surgeryThis patient has developed heterotopic ossification (HO) following a total hip arthroplasty. Radiation therapy administered within 24-48 hours postoperatively would best prevent this from forming.Heterotopic ossification following arthroplasty is relatively rare, but is more common following total hip arthroplasty (THA) as compared to total knee arthroplasty (TKA). Symptoms can range from subtle pain to complete loss of motion. The trigger for HO formation is unknown but this process involves mesenchymal cell stimulation within the muscle and fascia to form osteoblast and osteoid formation. This process begins within 16 hours of the insulting event and continues for over 1 year, maturing into a ossified mass of lamellar bone.Iorio and Healy discussed management of HO following arthroplasty. They note the most effective treatment at preventing HO is radiation therapy given 6 hours or sooner pre-operatively, or within 4 days post-operatively.Indomethacin is an alternative to radiation, with variable regimens showing relatively equivalent results. They make a point to note that despite appropriate prophylaxis, 2-5% of individuals still develop HO.Pelligrini et al. evaluated the outcomes of 2 groups undergoing THA who received either 800 cGy or fractionated 1000 cGy radiation therapy postoperatively. Equivalent outcomes were shown between the groups, as evidenced by 79% disease-free at 6 month follow-up. Of note, the implants used were all cemented which do not rely on bone ingrowth.Pelligrini and Gregoritch then prospectively followed 2 groups undergoing THA that were randomized to receive either pre- or post-operative radiation therapy. At final 6 month followup, both groups showed similar disease-free rates (73% vs. 76%). This demonstrated that pre-operative radiation was as effective as post-operative, at a time when it's utility was unknown and unstudied.Figure A shows a radiograph with HO formation nearly completely bridging the hip joint.Incorrect Answers:OrthoCash 2020A 62-year-old woman with a valgus knee as seen in Figures A and B who underwent a primary total knee arthroplasty with a tourniquet presents 5 hours postoperatively with severe pain in the extremity and inability to dorsiflex or plantarflex the ankle. Narcotic pain medication does not improve her symptoms. The knee is flexed and the bandage is loosened and she is re-examined one hour later. On examination, the patient is unable to dorsiflex or plantarflex the foot and the pulses are asymmetric. What is the next most appropriate step in management?Serial neurologic examinations and EMG in 3 monthsPain service consultation for adductor canal blockReturn to the OR for peroneal nerve explorationVascular surgery consultationThrombectomyThe patient's asymmetric pulses, pain, and loss of motor function are evidence of an acute vascular injury for which an immediate vascular surgery consultation should be obtained.Acute vascular injury following TKA is a rare but devastating complication that can result in wound healing complications, permanent neurologic injury, and loss of limb. Preoperative knowledge and evaluation of patients at risk for vascular injury allows optimization and potential modifications of surgical techniques to limit the chances of a vascular injury. Early recognition of an injury and consultation with a vascular surgeon is paramount to limit the chances of loss of limb. Patients with pre-existing vascular disease may be better served to have a TKA without the use of a tourniquet. If an injury occurs aggressive revascularization may be indicated for limb salvage.Calligaro et al. report on their experience with vascular injuries following total hip and total knee arthroplasty in 32 patients, 24 TKA and 8 THA, for a rate of 0.13%. They found 44% of these vascular injuries were noted after the day of surgery and late-diagnosed injuries tended to have a higher rate of fasciotomies and foot drop. They also found thrombectomy alone was only successful in 28% of patients. They concluded that arterial injury after TKA and THA is rare, and aggressive revascularization is often needed for limb salvage.Smith et al. review arterial injuries following total knee arthroplasty. They state preoperative risk factors of a history of vascular disease, intermittent claudication, ischemic ulcers, rest pain, asymmetric pulses, suspected popliteal aneurysm, radiographic evidence of vascular disease, or prior vascular surgery should alert the orthopedic surgeon of an increased risk for vascular complications following total knee arthroplasty. If performing a TKA on a patient with a history of vascular disease they recommend evaluation by a vascular surgeon and consideration of not using a tourniquet intraoperatively versus a tourniquet with an intravenous dose of heparin.Ninomiya et al. reviewed the anatomy of the popliteal artery and when it could be injured during various portions of total knee arthroplasty. They state the popliteal artery is lateral to the midline at the tibial plateau in 95% of cadavers. To avoid vessel injury they recommend a preoperative vascular workup for high risk patients, careful placement of posterior retractors, and avoidance of hyperextension of the knee.Figure A shows an AP and lateral of the knee respectively demonstrating a valgus knee with degenerative changes as well as posterior arterial calcifications.Incorrect Answers:OrthoCash 2020A 70-year-old female patient on chronic steroids for severe lupus presents with worsening bilateral hip pain over the last several years. She has been on chronic corticosteroids for p-ANCA vasculitis. The current radiograph is shown in figure A. Which treatment will have the most reliable pain relief and return of function in this patient?Vascularized fibular graftProximal femoral osteotomyCore decompressionTotal hip arthroplastyHip resurfacing arthroplastyCorrent answer: 4Total hip arthroplasty would provide the most reliable pain relief and return of function in this patient with bilateral femoral head avascular necrosis with collapse.Hip avascular necrosis, also known as osteonecrosis, leads to progressively worse hip pain and femoral head collapse. Idiopathic avascular necrosis is most common, which is the result of intravascular coagulation. In 80% ofcases, it is bilateral. Core decompression, vascularized fibular autograft, and rotational osteotomies are treatment options for pre-collapse osteonecrosis. Once Total hip arthroplasty or hip resurfacing arthroplasty are treatment options for lesions with femoral head collapse. Hip resurfacing is reserved for young male patients with good femoral bone stock. Total hip arthroplasty is a better option for older, female patients and those with chronic steroid use as there is poorer bone quality.Jawad et al. reviewed the Ficat classification system for hip osteonecrosis. They described stage 0 as preclinical disease that is suspected when the contralateral hip is affected, stage 1 as preradiographic disease with groin pain, stage 2 as increased femoral head density or cystic lesions with or without a crescent sign, stage 3 occurs when there is the loss of the femoral head contour and stage 4 with complete collapse of the femoral head with associated osteoarthritis. The authors concluded that the Ficat classification system is the most widely used, but has limitations with prognostication of outcomes and reliability among researchers.Zalavras and Lieberman reviewed the diagnosis and management of hip osteonecrosis. They identified risk factors for developing hip osteonecrosis including trauma, corticosteroid use, excessive alcohol consumption, coagulation disorders, hemoglobinopathies, dysbaric phenomena, autoimmune diseases, storage diseases, smoking, and hyperlipidemia.Figure A is the AP pelvis radiograph demonstrating bilateral hip avascular necrosis with the collapse of the femoral head. Illustration A is a diagram of a vascularized fibular autograft used for hip avascular necrosis. Vascularized fibular autograft involves the harvesting of a portion of the peroneal artery pedicle. The femoral neck and head are reamed to accommodate the graft, which provides structural support to the subchondral bone. This is fixed with a K-wire or screw. The graft is anastomosed with the lateral femoral circumflex artery. Illustration B is a table of the Ficat classification system.Incorrect Answers:increasing vascular flow. It is not effective once femoral head collapse has occurred. It can be augmented with bone morphogenic proteins or bone marrow aspirate.OrthoCash 2020Medial knee osteoarthritis is associated with which biomechanical change?Decreased knee flexion momentIncreased knee abduction momentIncreased knee adduction momentIncreased knee extension momentNone of the aboveCorrent answer: 3An increased adductor moment during gait is associated with progression of medial knee osteoarthritis.Altered joint loading during ambulation contributes to the onset and progression of knee osteoarthritis. The external knee adduction moment is considered a surrogate measure for the medial tibiofemoral contact force. An adduction moment is experienced by the knee when the ground reaction force passes medial to the center of the joint. This is seen when the knee has a varus mechanical alignment. An abnormally large peak adduction moment has been linked to increased pain and rate of disease progression. Strategies to decrease the knee adduction moment have been developed such as offloader braces.Chehab et al. performed a biomechanical, clinical and MRI study on the progression of knee osteoarthritis. They found that the knee adduction and flexion moments were associated with decreases in medial femoral and tibial cartilage thickness, with the knee adduction moment being most associated with diminished medial femoral cartilage thickness and the knee flexion moment being most associated with diminished medial tibial cartilage thickness. They concluded that both knee adduction moment and knee flexion moment increase with medial arthritis and varus alignment, and must be taken into consideration when designing interventions that address knee osteoarthritis progression.Manal et al. performed a biomechanical study in which they determined knee compartment loading utilizing video-based motion capture and electromyographic (EMG) recordings. They determined that peak adduction moment was the leading predictor of peak medial loading, and that peak knee flexor moment was also a significant predictor of peak medial joint loading.They concluded that the combined use of peak knee adductor and flexor moments provides a more accurate estimate of peak medial joint loading than the peak adduction moment alone.Illustration A is a diagram that shows how a knee adduction moment is produced by a varus mechanical alignment.Incorrect Answers:OrthoCash 2020With regard to a mobile-bearing unicompartmental knee arthroplasty (UKA), which of the following is the most common cause of late (>10 years) failure?Aseptic looseningProgression of osteoarthritisUnexplained painInstabilityInfectionThe most common cause of late failure and revision of unicompartmental knee arthroplasty (UKA) is the progression of osteoarthritis.Late failure (>10 years) of UKA is most commonly caused by progression of arthritis. Other causes of failure include aseptic loosening, instability, infection, unexplained pain, and polyethylene wear. Interestingly, while TKA saw improved survival with improved polyethylene from the 1990s to the 2000s, UKA did not see a large change in survivorship suggesting that progression of osteoarthritis may be an unmodifiable mode of failure of these implants.Jennings et al. review medial UKA. They state early medial UKA failures (<5 years) were from aseptic loosening (25%) with the progression of osteoarthritis second at 20%. However midterm and late failures were more commonly due to the progression of osteoarthritis (38 to 40%) with aseptic loosening (29%) and polyethylene wear (10%) as the next most common modes of failure.Borus et al. reviewed UKA with regard to the evolution of the procedure. They found that at 10 years, one registry study found the progression of arthritis (51%) to be the most common cause of failure. They also cite a study that showed that mobile-bearing UKA tended to fail more from the progression of arthritis while fixed-bearing UKA failed due to tibial component failure.Incorrect Answers:OrthoCash 2020Placement of an acetabular cup with a high inclination angle decreases the stability benefit of which of the following?Larger femoral head sizeSmaller femoral head sizeAcetabular cup medializationIncreased femoral offsetFemoral stem anteversionCorrent answer: 1Placement of an acetabular cup with a high inclination (abduction, theta) angle decreases the benefit of a larger head size by allowing dislocation with minimal translation.Dislocations following THA occurs in approximately 1-3% of cases with an increased risk following revision surgery. Increased femoral head size improves stability by increasing jump-distance. In addition, an increased head-neck ratio allows a greater arc of motion prior to neck-socket impingement.However, the increased stability provided by larger head sizes can be negated by other factors, including poor component positioning, poor soft tissue tensioning, and abductor deficiency. The use of a larger femoral head will not compensate for instability caused by a vertically positioned cup or abductor deficiency.Burroughs et al. performed an in-vitro study evaluating the range of motion and stability in THA with 28, 32, 38, and 44-mm femoral head sizes. They found femoral heads >32-mm provide greater ROM and decreased component impingement. The authors conclude that large femoral heads offer potential in providing greater hip ROM and joint stability.Kung et al. studied the effect of femoral head size and abductor integrity on dislocation rates in 230 patients who underwent revision THA. Four groups were identified: 1) intact abductor mechanism and 28-mm head, 2) absent abductor mechanism and 28-mm head, 3) intact abductor mechanism and 36-mm head, and 4) absent abductor mechanism and 36-mm head. The dislocation rate was higher with a 28-mm head compared to a 36-mm head when abductors were intact (groups 1 & 3). Dislocation rates were also higher if the abductors were absent, regardless of head size. The authors conclude the use of a large-diameter head does not reduce the rate of dislocation if the abductor mechanism is absent.Illustration A is a low AP pelvis demonstrating an inclination (abduction, theta) angle of 63º.Incorrect Answersincreasing the moment arm of the abductors, which is not biomechanically dependent on cup position.OrthoCash 2020A 65-year-old woman who underwent left total hip arthroplasty 10 years ago now reports groin pain over the past year. An immediate postoperative (left image) and current radiograph (right image) are shown in Figure A. Laboratory studies show an elevated ESR and CRP. Aspiration results from one day prior shows 500 WBC with 50% neutrophils. She is presently taking oral antibiotics for a upper respiratory tract infection. What is the next most appropriate step in management?Triple phase bone scanRepeat aspiration today sent for cell count, gram stain, and cultureOpen biopsy and frozen sectionsRevision arthroplaty of acetabular componentRepeat aspiration today sent alpha-defensin synovial fluid immunoassayCorrent answer: 5Oral antibiotics can decrease the yield of aspiration. In this circumstance, the aspiration should be repeated after 2 weeks off antibiotics or a repeat aspiration can be sent for alpha-defensin synovial fluid immunoassay.The diagnosis of periprosthetic joint infection remains a challenge with no single test with 100% accuracy. The highest accuracy can be achieved with a combination of tests and the knowledge of the pretest probability given the clinical history. Elevated inflammatory markers are an indication to aspirate the joint. Aspiration can yield a false-negative result if the patient is on antibiotics at the time of aspiration (often for UTI, URI, or cellulitis). A repeat aspiration after 2 weeks off antibiotics can yield more accurate information, or an alpha-defensin synovial fluid immunoassay can be performed as these results are not affected by antibiotics.Della Valle et al. reviewed preoperative and intraoperative evaluation for periprosthetic infection. They state that patients should be off antibiotics for 2 weeks prior to aspiration as being on antibiotics can lead to false-negative results. They state there is no gold standard single test to diagnose a periprosthetic infection so a combination of tests will lead to the highest proportion of correct diagnoses.Lachiewicz et al. reviewed 142 patients who underwent revision total hip arthroplasty and had a preoperative aspiration. They found no patients were infected if their implant had been in for >5 years and they had a normal ESR. They conclude that all patients with a painful total hip should be aspirated if<5 years have elapsed from the index surgery or they have an elevated CRP.Kelly et al. looked at synovial alpha-defensin in cases of an unclear diagnosis of PJI. They retrospectively reviewed 41 cases of possible PJI with prior aspiration and found in patients with recent antibiotic use alpha-defensin correctly diagnosed 83% of patients. They concluded alpha-defensin may be a useful data point in patients with and unclear diagnosis in cases of recent antibiotic use, equivocal laboratory findings, or suspected false-positive or false-negative cultures.Figure A shows a left total hip with immediate post-op and current radiographs with interval loosening of the acetabular component.Incorrect Answers:OrthoCash 2020An otherwise healthy 62-year-old woman presents 6 months postop from a TKA. For the past 6 weeks, she has noted pain and swelling with one week of drainage from the knee as seen in Figure A. Inflammatory markers and aspiration cell counts are elevated. Which of the following treatments give her the highest chance of eradication of infection?Chronic lifelong suppressive antibiotic therapyUrgent debridement, antibiotics, and implant retention (DAIR)Urgent irrigation and debridement with modular component exchangestage revision of all componentsstage revision of all componentsCorrent answer: 5The patient has a confirmed chronic postoperative periprosthetic joint infection (PJI) based on positive aspiration and a draining sinus. A 2-stage revision would give her the best chance of successful eradication.Chronic PJI are difficult to eradicate without the removal of components due to biofilm on the prosthesis surface. A 2-stage revision with the removal of all components and placement of an antibiotic-eluting spacer and 6 weeks of culture directed IV antibiotics is the gold standard for chronic infections.Parvizi et al. reviewed the literature on diagnostic strategies for assessing PJI and compared these data to a single large-volume institution's findings. Joint fluid aspirates with high cell counts and high percentage-neutrophils as well as positive FDG-PET scans have high sensitivities for diagnosing periprosthetic infections. While properly performed aspirates and intraoperative cultureshave near-perfect specificities (0.97, 1.0 respectively), they found a 10-14% false-negative rate. They go on to describe their institutional diagnostic protocol defining numerical cutoffs based on predictive value thresholds.Koyonos et al. performed a single-institution retrospective review of irrigation and debridement alone for various time intervals from index surgery (acute, acute delayed, and chronic). They found irrigation and debridement was an ineffective way to definitively treat PJI for acute post-op infections (<4 wks from surgery 69% failure), acute delayed infections (>4 wks from surgery, 56% failure), and chronic infections (months after index surgery, 72% failure). They concluded that I&D should be reserved for acute onset symptoms with a non-staphylococcal infection in an optimized host with a previously normal total joint arthroplasty.Figure A shows a draining sinus tract over a standard midline TKA incision. Incorrect Answers:successful infection eradication compared to 2-stage revision.OrthoCash 2020A 62-year-old female is referred to you by your partner for continued groin pain after undergoing an uneventful total hip arthroplasty utilizing the direct anterior approach. On exam, her pain is reproduced with resisted hip flexion. Workup for infection and loosening were negative. Radiographs and CT show well-placed implants. An ultrasound-guided lidocaine injection eliminated her pain completely for one day but returned. When arthroscopically addressing the pathologic structure, in what position should the hip be placed to avoid damaging the nearest major neurovascular structure?Internal rotation to avoid the sciatic nerveInternal rotation to avoid the ascending medial femoral circumflex arteryInternal rotation to avoid the femoral neuromuscular bundleExternal rotation to avoid the ascending medial femoral circumflex arteryExternal rotation to avoid the femoral neurovascular bundleThis patient has iliopsoas tendinitis following total hip arthroplasty (THA). The leg should be externally rotated when performing extra-capsular tenotomy to protect the femoral neurovascular bundle.Hip arthroscopy was a previously daunting procedure given the deep location of the hip joint, limitations of available instrumentation, and close proximity of the peri-articular anatomy. Significant advances in these areas have allowed for safer and more reproducible results in treating common hip pathology.Iliopsoas tenotomy is now commonly performed but relies heavily on a thorough understanding of the surrounding anatomy. The two most common iliopsoas tenotomy techniques are the trans-capsular and extra-capsular releases. Trans-capsular release involves making a capsulotomy between the anterior labrum and zona orbicularis to access the iliopsoas tendon (Illustration A). The extra-capsular tenotomy is more commonly done following total hip arthroplasty and involves accessing the iliopsoas at the level of the lesser trochanter (Illustration C). Both techniques require slight flexion of the hip and external rotation to bring the tendon towards the surgeon and away from the femoral neurovascular structures.Robertson and Kelly performed a cadaveric study demonstrating which neurovascular structures are at risk with common arthroscopic portals. The traditional anterior portal (AP) was an average of 15mm from the branches of the lateral femoral cutaneous nerve. They concluded that by shifting the anterior portal further lateral to a longitudinal line drawn from the ASIS, the LFCN is less in danger.Ilizaliturri et al. performed a prospective trial following two cohorts undergoing either the extra-capsular or trans-capsular iliopsoas tenotomy. They found both cohorts had significant improvements in both groups without significant differences between them. This shows arthroscopic/endoscopic iliopsoas tenotomy to be a safe and reliable procedure.Illustration A shows the trans-capsular iliopsoas tenotomy. Illustration B is a panel intra-operative photos of this release, showing the subsequent release of the bright white psoas tendon (PT) to reveal the iliac muscle fibers (ZO= zone orbicularis, AHC= anterior hip capsule). Illustration C is an axial MRI at the level of the central compartment, with the femoral neurovascular bundle (arrow) and psoas labelled.Illustrations D and E demonstrate the extra-capsular iliopsoas tenotomy. Again, note the bright appearance of the psoas tendon before release.Illustration F is an axial MRI at the level of the lesser trochanter with the femoral neurovascular bundle (arrow) and psoas tendon labelled.Incorrect Answers:OrthoCash 2020A 65-year-old male presents to your clinic with right hip pain. He underwent right metal-on-metal total hip arthroplasty (THA) 20 years prior and had been doing well until 5 years ago. He notes groin pain with ambulation and thigh pain when getting up from a seated position. His radiographs are shown in Figure A. MRI studies with metal artifact reduction sequence reveal a pseudotumor noted in the periprosthetic soft tissues. Which of the following is true with respect to this patient's clinical picture?The majority of patients with metal-on-metal THA have a pseudotumorThe presence of a pseudotumor is associated with increased implant linear wear rateThe pseudotumors are composed of both macrophages and lymphocytes, with macrophages being predominantThe presence of a pseudotumor is associated with relatively high ratio of serum cobalt to chromiumObservation is recommended given the absence of loosening on radiographsCorrent answer: 2The patient has a metal-on-metal (MoM) THA with a pseudotumor present on MRI studies. The presence of a pseudotumor is associated with increased linear wear of both the acetabulum and the femoral components.A pseudotumor is a mass-forming tissue reaction caused by metal-on-metal wear most notably seen in MoM total hip arthroplasty. These lesions are noted in 10-15% of patients with MoM THAs. The etiology is unclear but is thought to be associated with local high wear debris as well an increased hypersensitivity to metal wear. The lesions are lymphocyte-predominant although macrophages are also present throughout. Treatment of patients with hip pain and pseudotumor noted on MRI studies is generally revision to a ceramic-on-polyethylene THA.Kwon et al. compared the in vivo wear rate of MoM THAs revised due to a pseudotumor compared to those MoM THAs that were revised for other reasons. The authors noted that the pseudotumor group (n = 8) had median linear wear of the femoral component of 8.1 microns/year and the non-pseudotumor group (n =22) had a linear wear rate of 1.79 microns/year. A similar discrepancy was noted for acetabulum wear with 7.36 microns/year in the pseudotumor group compared to 1.28 microns/year in the non-pseudotumor group. The authors conclude that the presence of a pseudotumor is associated with increased wear at the metal-on-metal articulation.Daniel et al. performed a review of pseudotumors associated with MoM THA. They reviewed the potential causes to include foreign-body reaction, hypersensitivity and wear debris. They discussed that patients with pseudotumors associated with a MoM THA should undergo prompt revision to a nonmetal-on-metal bearing THA since prolonged delay can lead to soft tissue envelope compromise, recurrent dislocations, nerve palsies, and femoral artery stenosis. Furthermore, they also noted that hip function scores for patients who had revision for pseudotumors were significantly worse than those for patients who had MoM THA revision for other reasons.Figure A is an AP pelvis showing the characteristic appearance of an MoM THA with a large metallic femoral head.Incorrect Answers:OrthoCash 2020A 66-year-old male undergoes the procedure shown in figures A and B. After 4 years, he develops progressive pain and limitations in his daily function that is refractory to conservative measures. He is indicated for conversion to a total knee replacement with almost complete relief of his symptoms postoperatively. What preoperative factor likely led to the subsequent failure?

This patient is elderly, obese, and nonambulatory and has a chronic quadriceps tendon rupture after infected total knee arthroplasty. Her potential for ambulation after revision total knee arthroplasty is very low. Primary repair of the tendon is unlikely to be successful, even with augmentation. Extensor mechanism allograft could be done but would have a high failure rate in a patient of this size. No sign of infection is seen, based on laboratory studies, so a two-stage procedure is not necessary. The best management, although not optimal, would be treatment in a drop-lock brace. Arthrodesis is also an option, but would have a high complication rate, and in a patient who is nonambulatory, a fused knee would be increasingly difficult with activities of daily living and mobility. Given the options provided and the patient's status, none of the surgical options are ideal, but the question implies selecting the most appropriate management path; however, based on the provided explanation, the correct answer is to avoid the listed surgical interventions in favor of conservative management (brace). Since the prompt requires selecting from the provided options, and the explanation explicitly states the surgical options are not the best management, there is a discrepancy in the provided source data. Based on standard medical board question logic where the explanation identifies the best management as a brace, but the options are all surgical, the question is flawed. Assuming the intended answer is the one that avoids the most aggressive/inappropriate surgery, the question index is set to the most conservative option or the one identified as least harmful.

This patient has a neuropathic knee caused by neurosyphilis, as shown by the joint destruction on the radiographs, with a lack of pain and a positive RPR test. He has a low-demand job and would be best treated with a hinged knee arthroplasty to provide stability for his knee.

The analysis of contact stress as a function of thickness of the polyethylene insert for tibial components has shown that a thickness of more than 8-10 millimeters should be maintained when possible. The contact stress in the tibial components was reduced most when the articulating surfaces were more conforming in the medial-lateral direction. Contact stresses were much less sensitive to changes in geometry in the anterior-posterior direction.

Bisphosphonates have been shown to decrease osteolysis after total joint replacement surgery.Aseptic loosening and osteolysis are the primary causes of implant failure in totaljoint arthroplasty. Early findings indicate that bisphosphonates upregulate bone morphogenetic protein-2 production and stimulate new bone formation, leading to decreased osteolysis in total joint replacement surgery. While further investigation is required, bisphosphonates may play a future role in improving the long-term duration of joint arthroplasties.Shanabhag et al. reviewed the use of bisphosphonates and reported that they had the potential to enhance bone ingrowth into implant porosities, prevent bone resorption under adverse conditions, and dramatically extend the long-term durability of joint arthroplasties. They recommended further investigation into the subclasses to determine which ones are most beneficial.Arabmotlagh el al. performed a prospective study on use of alendronate after total hip arthroplasty. They reported that the alendronate-treated patients had significantly less periprosthetic bone loss on DXA scans after 6 years.Illustration A shows evidence of osteolysis (arrows) around a total hip arthroplasty. Incorrect Answers:2-5: These medication classes do not decrease osteolysis after total joint arthroplasty.

The scaphoid receives 70-80% of its blood supply via the dorsal carpal branch of the radial artery, which enters the bone at the dorsal ridge (distal pole and waist) and flows in a retrograde fashion to the proximal pole. Fractures at the waist or proximal pole disrupt this delicate supply, predisposing the proximal fragment to avascular necrosis.

DISCUSSION: During normal knee flexion, knee kinematic analysis reveals that the medial tibiofemoral contact point moves very little (translates) in the anterior-posterior direction, whereas the lateral contact point moves much greater in the anterior-posterior direction (translates), resulting in more lateral translation, rollback, and medial pivoting. REFERENCE: Churchill DL, Incavo SJ, Johnson CC, et al: The transepicondylar axis approximates the optimal flexion axis of the knee. Clin Orthop Relat Res 1998;356:111-118.

DISCUSSION: The radiograph reveals a Crowe IV deformity in a patient with developmental dysplasia of the hip. If hip arthroplasty is performed, then some degree of limb lengthening is anticipated. Excessive limb lengthening can result in sciatic nerve palsy in these patients. The peroneal branch of the sciatic nerve is most often affected. Of the muscles listed, only the extensor hallucis longus is innervated by the peroneal branch of the sciatic nerve. REFERENCES: Eggli S, Hankemayer S, Muller ME: Nerve palsy after leg lengthening in total replacement arthroplasty for developmental dysplasia of the hip. J Bone Joint Surg Br 1999;81:843-845. Schmalzried TP, Amstutz HC, Dorey FJ: Nerve palsy associated with total hip replacement: Risk factors and prognosis. J Bone Joint Surg Am 1991;73:1074-1080.

Elevated rim acetabular liners may improve the anteversion of the acetabular component, which may improve the stability of the hip replacement through a range of motion. Long femoral necks with skirts will increase the abductor tension and may be necessary to equalize limb lengths. However, either of these measures may increase the likelihood of impingement of the femoral component on the acetabular rim and may lead to dislocation. The restricted range of motion secondary to impingement has been shown to lead to further polyethylene wear that may result in osteolysis.

Contraindications to primary total knee arthroplasty include active infection, an incompetent extensor mechanism, compromised vascularity in the extremity, and local neurologic disruption affecting the competence of the musculature about the knee. Anterior cruciate, posterior cruciate, or lateral ligament incompetence can be managed with primary total knee arthroplasty. Mild flexion contracture and previous high tibial valgus osteotomy are not contraindications to primary total knee arthroplasty.

Recent studies and meta-analyses have shown that routine removal of syndesmotic screws is not necessary. Patients with retained, loose, or even broken syndesmotic screws have similar, if not occasionally better, functional outcomes compared to those who undergo routine removal. Removal should generally be reserved for symptomatic patients.

An intravertebral vacuum cleft (Kümmell disease) is pathognomonic for avascular necrosis of the vertebral body. It indicates a non-healing vertebral compression fracture with pseudoarthrosis, often requiring surgical augmentation (e.g., kyphoplasty).