3. Adult Reconstruction (Hip & Knee) MCQs

osteotomy.OrthoCash 2020A 88-year-old female fell onto her right hip sustaining the fracture shown in Figure A. Past medical history is significant for mild dementia and moderate coronary artery disease. At baseline, she ambulates with a walker. There are concerns about her ability to maintain weight-bearing precautions following surgery. Which of the following is most appropriate for management of the femoral side?Revision total hip replacement with a proximally coated femoral stemOpen reduction, internal fixation with plate and cerclage wiresProximal femoral replacement with megaprosthesisImpaction bone graftingCortical strut allograft with cerclage wiringCorrent answer: 3The radiograph shows a Vancouver B3 periprosthetic fracture with poor proximal femoral bone stock. Given her age, co-morbidities, and dementia, the appropriate management of her condition would be a proximal femoral replacement with megaprosthesis. This can allow for immediate weightbearing in the post-operative period.Vancouver B3 periprosthetic fractures are fractures around or just below the tip of a loose stem with poor proximal femoral bone stock. Options for management of this fracture include a fully coated stem, a fluted tapered stem, a proximal femoral replacement with megaprosthesis, allograft-prosthesis composite, and impaction bone grafting. In elderly patients with comorbidities and an inability to maintain the strict weight-bearing precautions that impaction bone grafting and allograft prosthetic replacements require, proximal femoral replacement with a megaprosthesis is the best option.Duncan et al. were the originators of the Vancouver classification system forperiprosthetic fractures. Type A fractures are peritrochanteric, type B fracture are around the stem tip, and type C fractures are well below the stem tip.Parvizi et al. review the indications for proximal femoral replacements with megaprostheses. They conclude it is a reasonable option for elderly patients with massive proximal femoral bone loss. The most frequent complications are aseptic loosening and dislocation.Klein et al. identified 23 patients who underwent proximal femoral replacement for a Vancouver type-B3 periprosthetic fracture. At a follow-up of 3 years, 22 of 23 patients were walking with minimal pain. The most frequent complications were persistent drainage (2), dislocation (2), refracture (1) and acetabular cage failure (1).Figure A shows a Vancouver B3 periprosthetic fracture with loose stem and poor proximal bone stock. Illustration A shows an example of a proximal femoral replacement. Illustration B shows a radiograph of a proximal femoral replacement used for a failed total hip replacement with massive bone loss. Illustration C shows the Vancouver classification (A, B1, B2, B3, C)Incorrect Answers:OrthoCash 2020A minimal-incision technique with an incision no more than 10 centimeters has which of the following advantages compared to a standard incision for a total hip replacement?lower post-operative visual analogue pain scoreless transfusion requirementshorter length of staybetter cosmetic resultless pain medication requirementCorrent answer: 4Ogonda et al randomized patients to standard (16cm) versus MIS incision (<10 cm). They found no significant difference with respect to postoperative hematocrit, blood transfusion requirements, pain scores, or analgesic use.There were also no differences in early walking ability or length of hospital stay and no differences in component alignment.OrthoCash 2020What is an advantage of utilizing a 36-mm instead of a 28-mm femoral head in the setting of a revision total hip arthroplasty?Compensating for abductor deficiencyDecreasing volumetric wearDecreasing trunion stressDelaying neck-socket impingementCompensating for vertical cup placementCorrent answer: 4Increasing femoral head size delays neck-socket impingement, enhancing stability by increasing the excursion distance prior to dislocation.The optimal bearing in total hip arthroplasty (THA) should allow for the best stability and function while preserving implant longevity. Greater motion, stability, and patient satisfaction have been correlated with larger femoral head sizes. Stability is associated with an increased displacement distance in larger diameter heads prior to a dislocation event (increased jump distance) combined with a greater impingement-free range of motion. Although larger femoral head sizes are associated with greater volumetric wear and trunion stress (and possible taper corrosion), newer bearings such as ceramic-on-ceramic may help mitigate these factors.Kung et al. examined the effect of femoral head size and abductor integrity on dislocation events after revision THA. They separated 230 patients who underwent revision THA into 4 groups: (1) intact abductors mechanism + 28-mm femoral head, (2) absent abductor mechanism + 28-mm femoral head,(3) intact abductor mechanism + 36-mm femoral head, and (4) absent abductor mechanism + 36-mm femoral head. They found that in patients with intact abductor mechanisms, the 36-mm femoral head was associated with a lower dislocation rate with 6-month minimum follow-up; femoral head size did not reduce dislocation events in patients with deficient abductor mechanisms.Burroughs et al. performed an in-vitro study evaluating the range of motion and stability in THA with 28-44-mm femoral head sizes. They found thatfemoral heads >32-mm provided for greater ROM and decreased component impingement. For these reasons, the authors conclude that large femoral heads may be beneficial in revision THA.Illustration 1 demonstrates the increased jump distance when utilizing a larger diameter femoral head. Illustration 2 demonstrates a greater impingement-free range of motion with a larger femoral head.Incorrect Answers:OrthoCash 2020A 65-year-old male is now 6 weeks status post an uncomplicated total knee arthroplasty. Figures A and B represent his x-rays at today's visit. His primary complaint is knee stiffness. His current passive range of motion is 0-80 degrees, compared to 120 degreespreoperatively, and he has failed to improve with physical therapy. He is otherwise afebrile, has no incisional erythema or pain, and CRP is within normal limits. Manipulation under anesthesia (MUA) will provide the largest improvement in flexion if performed before which of the following:Before 6 weeksBefore 12 weeksBefore 26 weeksBefore 34 weeksOutcomes after MUA are equivalent if performed within 1 year of surgeryCorrent answer: 2Manipulation under anesthesia (MUA) yields the greatest gain in flexion and improvement in overall range of motion if performed within 12 weeks postoperatively.Post-operative knee stiffness (flexion < 90 degrees) occurs in 1.3%-12% of patients who undergo TKA. The preoperative risk factors for stiffness include decreased preoperative range of motion, age, diabetes mellitus, and socioeconomic status. Surgical factors can also contribute, includingoverstuffing the patellofemoral joint, tight flexion/extension gaps, and excessive tightening of the extensor mechanism. If left untreated, loss of flexion negatively impacts functional outcomes, patient satisfaction, and ability to perform activities of daily living. MUA is considered the initial management for patients with flexion less than 90 degrees.Issa et al. studied the optimal timing of MUA. They found that patients undergoing MUA before 12 weeks had a significantly higher mean gain in flexion (36.5° versus 17°), higher final range of motion (119° versus 95°), and higher Knee Society objective (89 versus 84 points) and function scores (88 versus 83 points) than those who had late manipulation under anesthesia (after 12 weeks). There was no statistically significant difference between MUA before 6 weeks vs MUA before 12 weeks.Desai et al. similarly demonstrated that maximum flexion gains were achieved when MUA was performed between 12-14 weeks post-operatively. They also demonstrated that there is no benefit to multiple manipulations, with no observed flexion gain after the initial intervention.Incorrect Answers:OrthoCash 2020A 51-year-old male presents with worsening left hip pain over the past 8 months. The patient reports hip surgery 5 years prior as seen in Figures A and B. His CRP level is within normal limits, ESR is at the upper limit of normal, and automated cell count following a hip aspiration yields a WBC of 15,000/µL (rr, 4500-11000µL) and 85% PMNs. Metal ion testing reveals elevated serum cobalt and chromium levels. What is the next best step?Manual cell count of synovial fluidstage revision arthroplastyAcetabular cup revision with bone graftingFemoral revision with cerclage wire placementHip arthrodesisThe patient has had a metal-on-metal (MoM) hip resurfacing with osteolysis. It is likely his WBC count is falsely elevated secondary to metal debris and corrosion. The next best step is a manual cell count to evaluate for metal debris, clots, fragmented cells, or other defects preventing accurate automated cell count.Diagnosis of infection in the setting of MoM bearing surface can be difficult given very similar presentations. Typical workup includes CRP, ESR, synovial fluid WBC, and differential. Metal debris and corrosion reactions can confound the synovial fluid analysis leading to falsely elevated WBC counts in cases of aseptic failure. Prosthetic joint infection (PJI) and metallosis can occur concurrently so aggressive diagnostic testing is important for surgical decision making. Manual cell count of synovial fluid samples can identify metal debris and avoid false positives from automated cell testing. Supplementary tests, such as MARS MRI, metal ion levels, manual cell count, and repeat aspiration, can help guide appropriate management in these scenarios.Yi et al. investigated ESR, CRP, synovial WBC and differential in diagnosing PJI in the setting of MoM hips or non-MoM hips undergoing revision for corrosionor full thickness wear. They found that synovial fluid WBC count can be confounded by inaccurate automated cell counts secondary to foreign material and degenerating cells. They conclude that diagnosis of PJI in the setting of failed MoM bearings or corrosion is difficult due to falsely positive synovial fluid WBC.Carrothers et al. evaluated the prevalence of complications of hip resurfacing arthroplasty. They found the most common complication was fracture of the femoral neck, followed by loosening of the acetabular component, femoral head collapse, loosening of a femoral component, infection, aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL), loosening of both components, and malposition of the acetabular component. They conclude that knowledge of complications following hip resurfacing is important to help select patients and counsel them on risks prior to surgery.Figures A and B show a metal-on-metal hip resurfacing with supra-acetabular osteolysis.Incorrect Answers:OrthoCash 2020An 87-year-old female presents with longstanding knee pain. The structures identified in Figure A are formed through the pathologic activation of endochrondral ossification. The pathway involved in this process involves which of the following signaling molecules?Indian hedgehog (Ihh)Peroxisome proliferator-activated receptor gamma (PPARG)Receptor activator of nuclear factor kappa-ligand (RANKL)Osteoprotegerin (OPG)SclerostinOsteoarthritis and formation of osteophytes are felt to be mediated by the differentiation of quiescent chondrocytes through the Indian hedgehog signaling pathway.Indian hedgehog (Ihh) is an important mediator of chondrocyte and osteoblast differentiation in prenatal endochondral bone formation. Adult articular cartilage without osteoarthritis does not have active Ihh signaling. However, Ihh and its downstream signaling proteins have been found to be unregulated in osteoarthritic joints. Ihh may play an important role in activating endochondral ossification leading to some of the clinical features of osteoarthritis (osteophytes and subchondral cysts). Modulation of Ihh has therapeutic potential in the treatment of osteoarthritis.Maeda et al. studied mice with Ihh genes ablated from postnatal chondrocytes.They found a loss of columnar structure, premature vascular invasion, and formation of ectopic hypertrophic chondrocytes in the growth plate. They concluded that Ihh is essential for maintained trabecular bone, skeletal growth, and articular cartilage.Wang et al. reviewed the molecular mechanisms associated with cartilage degeneration in osteoarthritis. The study found that upregulation of the Ihh signaling molecules leads to the development of osteoarthritis, similar to that found in injury-induced controls. Additionally, they found that inhibiting the Ihh pathway reduces the severity of injury-induced osteoarthritis in mouse models.Figure A shows a knee with varus deformity and severe medial sided arthritis with femoral and tibial sided osteophytes(red arrows).Incorrect Answers:OrthoCash 2020Figure 1 is the AP pelvis radiograph of a 55-year-old male with known hip dysplasia and chronic right hip pain. He has no prior surgical history and is otherwise healthy. Your initial plan is to reconstruct his hip center at the site of his true acetabulum. Your preoperative template demonstrates that your acetabular component will have 40° of abduction, 15° of anteversion. However, there will be 25% uncoverage at the superolateral margin. What is the most appropriate next step to ensure adequate cup fixation?Increase the abduction angle to 60 degrees for better coverageMedialize the acetabular component beyond the medial wall for improved coverageElevate the hip center in search of better bone stockAccept 25% uncoverage and proceed with total hip arthroplasty as templatedUse cement augments to improve superolateral coverage of the acetabular componentThe most appropriate next step is to proceed with total hip arthroplasty (THA) as templated. Less than 30% of uncoverage is acceptable and has not been associated with increased rates of aseptic loosening.Dysplasia of the hip broadly refers to abnormal development of the hip that leads to poor acetabular coverage of the femoral head. The characteristic pelvic deformities of dysplasia include a retroverted acetabulum with bone loss at the superolateral margin. As a result, there is often insufficient bone stock to provide complete coverage of the acetabular component when placed at the true hip center. Insufficient coverage (<60-70%) can lead to a lack of initial stability and early failure. If the pre-operative template suggests extreme superolateral bone loss, the surgeon must then consider alternative methods of achieving satisfactory fixation, including downsizing the acetabular component size, medializing or elevating the hip center, or use of trabecular metal augments or cement augmentation for better coverage.Haddad et al. discuss pre-operative considerations when performing primary total hip arthroplasty on dysplastic hips. The literature review suggests thatless than 30% uncoverage does not increase the risk of aseptic loosening.Paavilainen et al. studied the short-term outcomes on 100 cementless total hip replacements in severely dysplastic hips. They describe the importance of exposing the proximal aspect of the pubic and ischial bones since the pelvic wall is usually hypoplastic, and the use of augmentation when the superolateral rim was deficient. Overall, their outcomes with cementless total hip replacements were equivalent to cemented prostheses.Figure A is an AP pelvis radiograph demonstrating a dysplastic right hip. Illustration A is a T1-weighted coronal MRI of a hip. Hip dysplasia can be assessed using the center-edge angle, the angle formed between a vertical line through the center of the femoral head and a line connecting the center of the femoral head with the lateral edge of the acetabulum. Less than 20° is one marker of hip dysplasia. Illustration B demonstrates the concept of joint reactive forces. Joint reactive force is minimized when the moment arm of body weight and abductor tensioning are balanced. Anatomic changes that reduce abductor tension such as elevating the hip center, decreasing femoral head size, and increased valgus neck angle increase the joint reactive force.Incorrect Answers:OrthoCash 2020A 65-year-old man presents to your clinic with chronic, progressive knee pain. Figure A is an x-ray of his right knee. He would like to pursue non-surgical treatment options. The AAOS clinical practice guidelines on the treatment of symptomatic knee arthritis support which of the following with "strong evidence"?NSAIDs; tramadolWeight loss; arthroscopic debridementWeight loss; intra-articular steroid injectionsValgus-offloading brace; glucosamine chondroitin injectionsTramadol; acupunctureThe AAOS clinical practice guidelines (CPG) summary "strongly" recommends tramadol or NSAIDs for the treatment of symptomatic knee osteoarthritis.Symptomatic knee osteoarthritis is widespread, with an incidence of 240 people per 100,000. Symptoms are often progressive, though addressing the modifiable risk factors of muscle weakness, large BMI, and repetitive loading can help with pain control. Definitive management is total knee arthroplasty, however, non-operative interventions are often successful in delaying surgery, particularly in younger patients.The AAOS Clinical Practice Guideline Summary performed a systematic review of the available literature to propose evidence-based guidelines for the management of symptomatic knee osteoarthritis. The current guidelines show strong support for the engagement in physical activity (such as guided physical therapy), non-steroidal anti-inflammatory drugs, and Tramadol for the management of symptomatic osteoarthritis. The Clinical Guidelines provided “strong” evidence against acupuncture, glucosamine and chondroitin, hyaluronic acid, and arthroscopy with lavage or debridement.Fishman et al. performed a double-blind, randomized study of 552 patients studying the efficacy of Tramadol vs placebo in the management of arthritic knee pain. Tramadol demonstrated a statistically significant improvement in knee pain over placebo as reported by the Patient Global Rating of Pain Relief Scale.Incorrect Answers:OrthoCash 2020An 82-year-old healthy male presents to the ED with right leg pain and inability to bear weight after a fall from standing. He has a historyof revision right total knee arthroplasty performed 5 years ago and was doing well until his fall this morning. On exam, he is able to actively extend his knee, though limited by pain, and is neurovascularly intact. Figures A-B are radiographs of his distal femur. What is the most appropriate treatment?Retrograde intramedullary nailRevision total knee arthroplasty with a stemmed femoral componentNonoperative management with application of a long leg castOpen reduction and internal fixation with a lateral plateAntegrade intramedullary nailCorrent answer: 4Open reduction and internal fixation with a lateral plate is the most appropriate treatment for this supracondylar periprosthetic femur fracture above a well-fixed total knee arthroplasty (TKA).Supracondylar periprosthetic femur fractures are defined as fractures within 15cm of the joint line or within 5cm of the proximal end of the implant in the case of a stemmed component. Risk factors include rheumatoid arthritis, neurologic disorders, steroid use, anterior cortical notching of the femoralcomponent and revision TKA. Nonoperative management usually requires long-term immobilization, which can result in significant loss of knee range of motion (ROM). Therefore, surgical treatment is often preferred. An acceptable outcome is > 90° of knee ROM, fracture shortening < 2cm, varus/valgus malalignment < 5°, and flexion/extension malalignment < 10°.Su et al. performed a literature review of the management of periprosthetic femur fractures above a TKA. First, it is crucial to determine the stability of the femoral component. An unstable femoral component requires either revision TKA or distal femoral replacement, depending on the quality of the distal femoral bone stock. A fracture with a stable femoral component can be well fixed with a buttress plate or retrograde intramedullary nail. In a series of 12 patients undergoing fracture fixation with lateral plate, all patients healed and returned to pre-fracture ambulatory status.Zehntner et al. studied the surgical outcomes of buttress plating in 6 supracondylar femur fractures above TKA. There was no nonunion, loss of fixation or infection. Knee ROM averaged 97°, and all patients were ambulating postoperatively.Figures A and B represent AP and lateral radiographs of a supracondylar periprosthetic femur fracture above a stemmed TKA. Illustrations C and D represent AP and lateral radiographs of a supracondylar periprosthetic femur fracture above a stemmed TKA status post repair with lateral plate.Incorrect Answers:OrthoCash 2020A 60-year-old woman presents for follow-up two weeks after right total knee arthroplasty. She complains of significant anterior knee pain after fall from standing onto a flexed knee. On physical exam, her passive range of motion is 0-120 degrees and she is stable to varus and valgus stress. She is able to achieve full extension with active range of motion, though she is experiencing severe pain. Lateral radiograph of the knee is provided in Figure A. What is the most appropriate next step?Non-operative management with long leg castClosed treatment with immediate active range of motionRemoval of patellar component with early active range of motionOpen reduction and internal fixation of patella with wire or screw fixationExtensor mechanism repair with Achilles allograft and revision of the patellaCorrent answer: 1The appropriate treatment for a transverse periprosthetic patella fracture with an intact extensor mechanism is closed treatment and immobilization in a long leg cast.Periprosthetic patella fracture after total knee arthroplasty is rare (incidence of 0.68%-5.2%) and is overwhelmingly secondary to a traumatic mechanism.Risk factors include excessive patella resection, use of cementless components, and elevated BMI. Broadly, the treatment algorithm for periprosthetic patella fracture depends on the stability of the implant and the involvement of the extensor mechanism. Ortiquerra and Berry classified periprosthetic patella fractures as intact extensor mechanism with well a fixed implant (Type I), extensor mechanism disruption with either a loose or stable implant (Type II), or intact extensor mechanism with a loose implant (Type III). Generally, fractures associated with component loosening or extensor mechanism injuries (Type II & Type III) require revision surgery and often yield poor results. Type I fractures are successfully managed non-operatively.Nam et al. reviewed the management of extensor mechanism complications intotal knee arthroplasty. They report excellent results in Type I peri-prosthetic patella fractures managed non-operatively, with only 1 failure in 37 patients. They propose a treatment algorithm based upon fracture pattern (transverse vs vertical), component fixation, and extensor mechanism integrity. Type I injuries with transverse fractures should be immobilized in long leg casts, whereas Type I injuries with vertical fractures are more stable and can benefit from early active range of motion.Cottino el al. similarly review the outcomes of peri-prosthetic patella fractures. They report a 50% complication rate and a 20-40% re-operation rate for type II and type III injuries, even with anatomic reductions.Figure A is a lateral radiograph of the knee that demonstrates a transverse peri-prosthetic patella fracture without component loosening. There is no obvious extensor mechanism injury and the prompt indicates extension is intact. Illustration A represents the peri-prosthetic patella fracture treatment algorithm as proposed by Nam et al. Illustration B represents the Ortiquerra and Berry peri-prosthetic patella fracture classification.Incorrect Answers:OrthoCash 2020A 68-year-old healthy male with a history of a right total hip arthroplasty 8 years prior presents with one year of right hip pain and several months of inability to bear weight. An AP pelvis radiograph is shown in Figure A. ESR is 8 mm/hr and CRP is 1 mg/L. What is the best treatment option?Cemented acetabular cup with morselized bone graftTwo stage revision with antibiotic spacerCup-cage construct with or without morselized bone graftDefinitive removal of hardware/Girdlestone procedureAnterior and posterior column plates with hemispherical uncemented cupCorrent answer: 3Cup-cage constructs have demonstrated excellent outcomes in patients with pelvic discontinuity and Gross type V acetabular defects.When treating chronic pelvic discontinuities, four general principles need to be addressed: 1) restoration of the acetabulum by reconnecting the ischium to the ilium, 2) optimizing contact of bleeding bone to component surfaces with ingrowth potential, 3) grafting osseous deficiencies, 4) obtaining a mechanically stable reconstruction to protect components until ingrowth is achieved. There are several different classifications of acetabular bone loss, though the Gross classification is unique in that it not only grades the degree of bone loss but also provides reconstructive options that may be considered (Illustration A & B). Due to the segmental bone loss associated with GrossTypes IV and V defects, cup-cage constructs are used to bridge segmental defects or areas of discontinuity.DeBoer et al. studied the long-term outcomes of 28 patients with pelvic discontinuity treated with custom triflange acetabular prostheses. They reported no instances of broken screws, implant migration, or component revision at 10 years. Complications included one partial sciatic nerve palsy and five patients with dislocation.Makinen et al. reviewed the role of cages in revision arthroplasty. In Gross Type V defects, cages provide mechanical stability to protect the acetabular cup until ingrowth is achieved. They report two case series following cup-cage reconstructions for pelvic discontinuity, demonstrating 88% survival at 44.6 months and 87.2% survival at 82 months. The survivorship of cage only constructs was 49.9% at seven years.Figure A demonstrates a failed right total hip arthroplasty with associated chronic pelvic discontinuity. Illustration A demonstrates the Gross classification for acetabular bone defects. Illustration B demonstrates the suggested reconstructive options for defects classified according to the Gross classification system.Incorrect Answers:OrthoCash 2020A 60-year-old male presents with significant left knee pain and end-stage osteoarthritis. He failed non-operative management and is requesting a total knee arthroplasty (TKA). His past medical history is significant for a left distal femur fracture that occurred when he was struck by a car 30 years prior. A standing, full-length radiograph of his left lower extremity is shown in Figure A. His femoral coronal plane deformity measures 28 degrees. When proceeding with a TKA, what must be done to address this patient's coronal deformity?Soft tissue balancing and intra-articular bone cutsDistal femoral medial closing-wedge osteotomyDistal femoral lateral closing-wedge osteotomyHigh tibial osteotomyHinged TKACoronal plane deformities of the femur >20 degrees require an extra-articular femoral osteotomy to achieve proper mechanical alignment when performing a TKA.Coronal and sagittal plane deformities of the femur less than 20 degrees can usually be addressed with intra-articular bone cuts and soft tissue balancing. Attempting to correct deformities greater than this without an extra-articular osteotomy can compromise ligamentous stability. This highlights the importance of careful pre-operative templating/planning and obtaining full-length, standing radiographs when clinically warranted. Although correcting severe deformities with staged or concomitant extra-articular osteotomies can be challenging, they are often successful when properly executed.Lonner et al. provided a retrospective case series and review article addressingsevere extra-articular deformities with simultaneous femoral osteotomy and TKA in patients with osteoarthritis. In their 10-patient series, they were successful in restoring coronal alignment within two degrees of anatomic in all patients. They suggest securing the femoral osteotomy site with a plate or locked intramedullary nail, depending on the osteotomy site.Rajgopal et al. presented a case series of TKA in 36 knees in the setting of extra-articular deformities. In this series, they treated all patients with intraarticular bone resection and soft-tissue balancing to address their deformities. Femoral-coronal, sagittal, and tibial-coronal deformities successfully treated included 11-18 degrees, 0-15 degrees, and 12-24 degrees, respectively.Figure A is a standing, full-length radiograph of the left lower extremity demonstrating a significant coronal plane deformity resulting from a previous distal femur fracture malunion. Illustration A is a left knee radiograph demonstrating an extra-articular distal femoral osteotomy with placement of a fluted, press-fit stem. Illustration B is the same patient at 3-year follow-up demonstrating a fully healed osteotomy and maintained hardware alignment.Incorrect Answers:OrthoCash 2020A 76-year-old female presents with right hip pain 6 years after total hip arthroplasty. She denies constitutional symptoms at this time. On physical examination, her incision is well healed. Current radiographs are shown in Figures A and B. In addition to a complete blood count (CBC), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR), an alpha-defensin immunoassay is ordered. What does the alpha-defensin immunoassay test for?The presence of an intra-articular, antimicrobial peptideThe presence of an antimicrobial peptide within serumThe presence of an intra-articular, pro-inflammatory markerThe presence of an intra-articular, pro-inflammatory cytokineThe presence of intra-articular leukocytosisCorrent answer: 1A synovial alpha-defensin immunoassay tests for the presence of an intraarticular, antimicrobial peptide.When there is suspicion of a periprosthetic infection, laboratory workup shouldinclude CRP and ESR. If suspicion remains after laboratory examination, an aspiration of the joint should be performed for cell count and culture. A fairly recent test developed to aid in the diagnosis of PJI is the synovial alpha-defensin immunoassay. Defensins are antimicrobial peptides that are active against many bacteria, fungi, and enveloped viruses. Alpha-defensin is an antimicrobial peptide which is abundant in neutrophils and macrophages. It is present in the natural local tissue response to infection. In the setting periprosthetic joint infection (PJI) the levels of intra-articular alpha-defensin increase substantially and may reach levels that can be detected by an immunoassay. Alpha-defensin may be more prone to false positive results in adverse local tissue reaction caused by a metal-on-metal arthroplasty.Bonanzinga et al. performed a prospective study to determine the reliability of the alpha-defensin immunoassay for diagnosing PJI. They aspirated hips and knees in all patients presenting with pain in both primary and revision arthroplasties. They found the sensitivity of the alpha-defensin immunoassay was 97%, the specificity was 97%, the positive predictive value was 88%, and the negative predictive value was 99% (95% CI, 96%–99%). They conclude that alpha-defensin appears to be a reliable test.Shinsky et al. performed a study to evaluate the utility of commonly available tests for determining the presence of PJI in patients undergoing revision total hip arthroplasty. 235 consecutive total hip arthroplasties undergoing revision were evaluated. They found that no hip in a patient with a preoperative ESR of<30 mm/hr and a CRP of <10 mg/dL was infected. They also conclude that a synovial fluid cell count of >3000 white blood cells/mL was the most predictive perioperative testing modality when ESR and CRP were elevated as well.Figures A and B are AP and lateral radiographs of the right hip, respectively, demonstrating a region of periarticular erosions around the proximal femoral stem.Incorrect Answers:OrthoCash 2020A 72-year-old male presents to your clinic with a 6-month history of left groin pain without preceding trauma. He previously underwent an uneventful left total hip arthroplasty 15-years prior at an outside institution. He has been ambulating with a cane for the last month due to pain. A left hip radiograph is obtained and presented in Figure A. Less than 4 centimeters of intact diaphyseal bone remains distal to the isthmus. An infection work-up is negative. Of the choices provided, what is the most appropriate management option at this time?Continued observationPlacement of a femoral cortical strut allograft and cerclage wiresFemoral revision with impaction grafting and a cementless femoral stemFemoral revision with a metaphyseal-engaging tapered stemFemoral revision with a modular fluted tapered stemCorrent answer: 5This patient has a Paprosky type-IIIB femoral defect (less than 4cm diaphyseal bone available for distal fixation) that can be revised with a modular fluted tapered stemFemoral revision with a modular fluted tapered stem is the preferred methodin the treatment of Paprosky type-IIIB femoral defects. Proximal femoral replacement, allograft prosthetic composite, resection arthroplasty, and impaction grafting may also be considered in the treatment of Paprosky type-IIIB and IV femoral defects. Impaction grafting involves creating a neomedullary canal by impacting cancellous bone chips into the femoral canal followed by cementation of the final femoral component.Valle et al. present a review article describing the Paprosky classification of femoral defects as well as treatment options. They differentiate a type-IIIA and IIIB defect as having >4 and <4 centimeters of intact diaphyseal bone available for distal fixation, respectively.Hartman et al. describe management strategies for femoral fixation in the setting of revision total hip arthroplasty. They review classification systems of femoral bone loss and provide an overview of various treatment options. The authors feel that type-II and IIIA defects can be effectively treated with cylindrical, extensively porous-coated implants, whereas IIIB defects can usually be treated with a modular fluted tapered stem.Figure A show a total hip arthroplasty with less than 4cm of diaphyseal bone available for distal fixation with extensive metaphyseal and diaphyseal bone loss. Illustration A shows a diagram of the Paprosky classification for femoral bone loss.Incorrect Answers:OrthoCash 2020An 85-year-old woman sustains a ground level fall. Her THA was done 25 years ago. She was previously ambulatory but with a significant limp. With regard to the femur specifically, what is the Vancouver classification and preferred treatment option?Vancouver C, revision to proximal femoral replacementVancouver B1, ORIF with impaction graftingVancouver AG, ORIFVancouver B3, revision to proximal femoral replacementVancouver B2, ORIF with femoral strut allograft augmentationCorrent answer: 4The periprosthetic femoral fracture should be classified as Vancouver B3 given the location around the femoral stem with very poor proximal femoral bone stock, thus making reconstruction of this bone unrealistic. The best treatment options for a B3 fracture would be revision of the stem to a proximal femoral replacement or proximal femoral allograft composite.The Vancouver periprosthetic classification system is one of the most useful classifications in orthopaedics as it can reliably guide treatment. Vancouver B1 or C type fractures confer a well-fixed stem and so ORIF would be thetreatment of choice. B2 and B3 fractures signify a loose femoral stem and so revision is necessary while B3 fractures have very poor proximal bone quality making any reliance on metaphyseal proximal bone for fixation or reconstruction futile.Klein et al. retrospectively reviewed 21 patients (mean age 79) with Vancouver B3 fractures treated with a proximal femoral replacement. At most recent follow-up, 20/21 patients were ambulatory with no or minimal pain.They note a relatively high complication rate (2 recurrent dislocators, 1 repeat fracture, 1 acetabular complication, 2 infections treated with I&D). However, given the circumstances and morbidity of non-operative management, they still recommend a proximal femoral replacement for this complicated patient group.Savvidou et al. offer a good review of proximal femoral replacement both for periprosthetic fracture and also revision THA with significant proximal bone loss. They emphasize the complications such as dislocation and aseptic loosening and offer recommendations for minimizing them such as a large femoral head, soft tissue repair, and preservation/repair of abductors.Figure A demonstrates a cemented total hip arthroplasty with significant osteolytic changes about both the femoral and acetabular components with multiple fractures around the grossly loose femoral stem. Taken from Klein et. al.Illustration A demonstrates an example of a proximal femoral replacement. Taken from Savvidou et al.Incorrect Answers:OrthoCash 2020Which of the following liner types have been associated with early acetabular component loosening?Figures B and CCorrent answer: 1Figure A is an illustration of a lateralized or offset acetabular liner which has been shown to have a higher rate of loosening with primary and revision total hip arthroplasty (THA).Extended offset polyethylene liners allow restoration of soft tissue tension by adding 4 to 10 mm of additional offset to the acetabular side. They translate the center of hip rotation laterally which will increase offset in the horizontal plane and add a few millimeters of additional limb lengthening in the vertical plane. The lateral translation of the center of rotation has been found to increase joint reaction forces and polyethylene wear. Additionally, this resultsin an eccentric loading pattern and leads to increased torsional forces at the liner-shell interface and the bone-implant interface. This may cause motion at the interface resulting in failure of ingrowth and early loosening.Glori performed a study to determine if torsion on an offset acetabular component may increase the risk of fixation failure. He found that a 70 kg person walking normally on a well-positioned 10-mm offset component will produce more torsion compared to a 4-mm offset component. Vertical cup placement was also found to increase torsion. He concludes that these torsional moments are comparable to moments shown to cause failure of the initial interference fit of cementless acetabular components in vitro. He suggests that after using an offset cementless acetabular component, one should initially limit weight bearing to minimize the risk of failure.Archibeck et. al reviewed 1919 patients with primary THA and 346 with revision THA to evaluate acetabular component loosening. A 7-mm offset acetabular liner was used in 120 of the primary and 100 of the revision THAs. The aseptic loosening rate in the primary THA group was 0.12% in the standard offset and 4.2% in the extended offset groups at a minimum of 2 years follow-up. The aseptic loosening rate in the revision group was 1.7% in the standard and 7% in the extended offset groups at a mean of 4 years follow-up. They conclude that offset acetabular liners have a high failure rate in primary and revision THA.Figure A is an illustration depicting an offset acetabular component. Figure B is an illustration depicting an oblique acetabular component or a face-changing liner. Figure C is an illustration depicting an elevated rim acetabular component or a lipped liner. Figure D is an illustration depicting a standard offset component.Incorrect Answers:OrthoCash 2020During a revision hip surgery, which of the following muscles labeled in Figure 1 can be transferred in the setting of an abductor deficiency?

This patient has osteonecrosis of the capitate. The MR images show evidence of osteonecrosis with decreased signal on the T1-weighted image. The radiographs are unremarkable, with the exception of lunotriquetral coalition, which does not necessitate treatment. The etiology of osteonecrosis of the capitate may be related to trauma, abnormal interosseous vascular supply, and hypermobility. Surgery is an option for patients with persistent symptoms despite immobilization. Vascularized bone graft should be considered in this scenario because there is no evidence of capitate collapse or arthritic change about the wrist. Free and local vascularized bone grafts have produced satisfactory results. Capitate excision with interposition arthroplasty is indicated for patients with proximal pole capitate collapse. Total wrist fusion is a salvage procedure and would be considered if there were evidence of collapse and arthritic change. PRC would leave the capitate articulating with the radius and is not indicated.

Increasing articular conformity increases the surface area for contact between the polyethylene and the femoral component. Advantages of this include lower peak contact stress within the polyethylene and less risk of polyethylene fatigue failure. Patellofemoral tracking is unchanged by increasing conformity unless gross component apposition is present. A potential disadvantage of increasing conformity includes some restriction in tibial rollback. Modest changes in conformity have not been shown to alter the rate of mechanical loosening. If conformity was increased to the extent of significant constraint, a potential increased risk of loosening would be expected, not a decrease. Design of modern TKAs includes a compromise in achieving enough constraint to lower polyethylene stress, without providing so much constraint as to limit kinematics and stress the fixation interfaces.

Recent literature supports retention of well-fixed cemented femoral components when revising loosened cemented acetabular components. Current literature also supports the use of cementless components for revision of loosened cemented acetabular components.

DISCUSSION: The radiograph shows that this patient has a high offset varus femoral morphology of both hips. Preoperative templating would identify this, and the surgeon should choose an implant system that has extended offset options to help match the native anatomy and biomechanics and minimize the risk of instability. Trialing a high offset neck, rather than a standard offset neck, is the next most appropriate step. Depending on the design of the implant system, this step can be accomplished by direct medialization of the femoral head, which would not affect leg length, or by lowering the neck angle, which would affect the leg length and would require a longer femoral head, because the leg lengths had previously been equal. Placement of a longer femoral head would likely improve hip stability but would also make the leg length uneven, which is a common cause of dissatisfaction after total hip arthroplasty. An offset acetabular liner also increases the leg length and does not correct the issue, which is on the femoral side. Trochanteric advancement is sometimes used as a treatment for instability but would be inappropriate as the next step in this setting.

DISCUSSION: Stiffness following total knee arthroplasty can be a disabling condition. There are many reasons for loss of knee motion following total knee arthroplasty. Technical errors, such as overstuffing of the patella, malpositioning of the components, and ligamentous imbalance, are all known to result in stiffness following total knee arthroplasty. In some patients with a possible genetic predisposition, aggressive arthrofibrosis may develop and result in loss of knee motion. In any patient who has deteriorating knee motion, particularly after revision arthroplasty, deep infection should be ruled out. Although on occasion surgical intervention may be required to address knee stiffness, the outcome of revision surgery is poor if no reason for stiffness can be determined.

DISCUSSION: The lateral radiograph reveals a triceps avulsion with a small portion of bone. Triceps weakness and insufficiency can be a symptomatic problem after total elbow arthroplasty and is probably underreported. Ulnar nerve neuritis, aseptic loosening, instability, and infection are all complications of total elbow arthroplasty but would not account for the radiographic findings.

DISCUSSIONThis patient likely has a soft-tissue reaction (pseudotumor) related to metal-on-metal articulation. Although the components are well positioned, patient gender and small head size are both known risk factors for failure of hip resurfacing arthroplasties. Metal ion levels are elevated but are not always markedly increased in the setting of a problematic metal-on-metal articulation. The patient should have a metal artifact reduction sequence MR imaging study to confirm the presence of a pseudotumor. Chronic infection is very unlikely in the setting of normal ESR and CRP findings. Impingement and lumbar disk disease would not explain the swelling around the hip.

A rectus snip during total knee arthroplasty has no effect on motion or strength at long-term follow-up. It has not been associated with extensor mechanism lag.

Operative exploration and decompression of the peroneal nerve-Five patients were treated by operative exploration and decompression of the peroneal nerve for peroneal nerve palsy complicating total knee arthroplasty (TKA). All patients had failed to demonstrate improvement in the peroneal nerve function despite extended conservative care. The procedure was performed five to 45 months after the index TKA. Patients were evaluated and graded preoperatively and postoperatively using the Modified Nerve Palsy Scale of Weber, Daube, and Coventry. All patients demonstrated improved nerve function. Four of five patients had full peroneal nerve recovery. All patients were able to discontinue their ankle-foot orthoses.This is a rarecomplication of TKA, and when conservative nonoperative measures do not lead to sufficient improvement in nerve function, consideration may be given to operative decompression of theperoneal nerve.

Peters et al reviewed the results of 37 hips in which a well fixed femoral component that had originally been implanted with first generation cementing techniques was left in place at the time of acetabular revision. There was no significant increase in loosening, infection, dislocation or polyethylene wear. The predicted rate of survival of the femoral component after revision of only the acetabular component was 88% at 48 months and 78°% after 88 months. This author recommends retaining a well fixed femoral component that has been implanted with 1st generation cementing techniques during acetabular revision.

Hemophilia A is an X-linked recessive deficiency of factor VIII that can lead to significant bleeding problems including recurrent spontaneous hemarthroses that can lead to synovitis and joint destruction. von Willebrand disease is a lack of von Willebrand factor that leads to decreased platelet aggregation; more commonly patients have mucosal bleeding and not hemarthroses. Vitamin K deficiency is not hereditary; it is typically attributable to inadequate dietary intake, malabsorption, and loss of storage sites from hepatocellular disease. Protein C and S deficiencies are autosomal-dominant diseases that lead to thrombosis, not bleeding, as protein C and S shut off thrombin formation.

The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following revision of failed metal-on-metal hip replacements.

DISCUSSION: In properly selected patients who have no or minimal tibiofemoral arthritis, the most common cause of early failure is patellofemoral instability secondary to uncorrected patellar malalignment, soft-tissue imbalance, or component malposition. Progression of tibiofemoral arthritis is also a leading cause of failure, but occurs late in about 25% of patients. Loosening of components has occurred in less than 1% of knees with cemented implants. A higher rate of loosening has been reported in cementless implants. REFERENCES: Lonner JH: Patellofemoral arthroplasty. J Am Acad Orthop Surg 2007;15:495-506. Argenson JN, Flecher X, Parratte S, et al: Patellofemoral arthroplasty: An update. Clin Orthop Relat Res 2005;440:50-53.

DISCUSSIONSimultaneous bilateral TKA accounts for approximately 6% of the TKAs performed in the United States and is more frequently performed for women. The incidence of pulmonary embolism in this group was between 0.57 and 1.14, according to a 1999 to 2008 registry-based study in the United States. There was not a significant change in incidence during that period. Hypoxemia alone is not an indication for advanced testing for pulmonary embolism. Winters and associates demonstrated that to avoid unnecessary testing, the use of a hypoxia algorithm is a reasonable first step. The use of pharmacologic agents and/or mechanical compressive devices for the prevention of venous thromboembolism in patients undergoing elective hip or knee arthroplasty and who are not at elevated risk beyond that of the surgery itself for venous thromboembolism or bleeding was given a Moderate grade of recommendation in the 2011 AAOS Clinical Practice Guideline, Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty. Various genetic factors are associated with increased risk for venous thromboembolic disease after TKA. A recent meta-analysis evaluated the genetic and polymorphism profiles associated with venous thromboembolism after arthroplasty. The mutation MTHFR/C677T/TT carried the highest risk (OR 2.36; 95% CI, 1.03-5.42, P = 0.04) for the gene mutations and polymorphisms studied. With the increased use of TXA as a blood-conservation strategy for total joint arthroplasty, there is a theoretical concern about an increased risk for venous thromboembolic disease. A recent study by Duncan and associates included 13,262 elective total joint arthroplasty procedures and demonstrated that TXA does not increase the risk of venous thromboembolism.

DISCUSSION: The patient has an extensor mechanism disruption with patellar tendon rupture. This injury is treated with extensor mechanism reconstruction in the setting of previous total knee arthroplasty. There is a reported high failure rate with attempted repair. Revision to hinge knee arthroplasty would provide implant stability but would not restore the extensor mechanism. The patient is relatively young and is working, so reconstruction would offer better long-term function than a drop lock brace, which can be better used in low-functioning patients with this type of injury. Extensor mechanism reconstruction historically has been accomplished with allograft material, but a novel technique using synthetic mesh also has proved successful in treating this difficult problem.

A common postsurgical problem after TKA is a sudden increase of pain that typically occurs about 2 to 3 weeks after surgery. ESR findings are not reliable during the acute postsurgical period. A CRP level exceeding 100 mg/L during the acute postsurgical period is a joint aspiration indication. If the patient does not have sepsis, there is no emergency. This pain is likely attributable to too much activity during physical therapy. Observation is recommended for this patient.

Figure 1 reveals an external rotation deformity of the right lower extremity. This deformity can have numerous causes, including extra-articular deformity. Figure 2 reveals a loose, subsided femoral component. Femoral stems typically subside into retroversion due to proximal femoral biomechanics, which cause a compensatory external rotation deformity. The combined findings from both images suggest an external rotation deformity most likely related to subsidence into retroversion.

Contemporary onlay-design trochlear prostheses in PFA replace the entire anterior trochlear surface. Previous inlay designs were inset within the native trochlea and carried a higher risk of catching and patellar instability, particularly in patients with trochlear dysplasia; they also generally have higher failure rates. The current most common mode of failure is progression of arthritis throughout the knee, in some series as high as 25% at 15 years. Aseptic loosening, particularly of cemented implants, is less common. Infection is an uncommon long-term complication. Patients considering PFA should be advised of the risk of arthritis progression.

Painful MOM THA and taper corrosion can cause substantial damage to a patient's hip if left untreated. In this case, the workup for a painful MOM THA starts the same as a workup for a painful metal-on- polyethylene bearing couple. Infection must be ruled out in every case with a set of inflammatory markers. If these markers are remotely elevated, this is an indication for joint aspiration. In patients with metal debris, the pathology report often indicates too many cells to count or cellular debris. Metal ion levels do not seem to correlate with prognosis. There are well-functioning patients with high ion levels and poor- functioning  patients  with  low  ion  levels.  Advanced  imaging  with  MARS  MRI  to  evaluate  for peritrochanteric fluid collection, a soft-tissue mass, or synovial/capsular hypertrophy will reveal signs of a metal reaction that indicate the need for a revision discussion. A CT scan can show more advanced bony destruction as an indicator of poor prognosis. These films can be used to determine the need for a structural graft or augments for reconstruction of bone loss attributable to metal debris.