3. Adult Reconstruction (Hip & Knee) MCQs

In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. The popliteus tendon is a primary stabilizer of the lateral compartment and its release can preferentially increase the flexion gap compared to the extension gap.

Dynamic patellofemoral joint contact measurements on cadaveric knees with simulated increased Q angle demonstrated that forces shifted to the lateral facet. The lateral shift in the patella was most pronounced from 40 to 90 degrees of flexion. At lower degrees of flexion, the lateral shift was significantly less. At higher degrees of flexion, the continued shift of the patella was not as pronounced.

Total knee replacement is a well-established surgery for diffuse, symptomatic osteoarthritis of the knee joint, and its efficacy has been shown in many studies. According to the 2008 AAOS Clinical Practice Guideline, Treatment of Osteoarthritis of the Knee, arthroscopy in the setting of existing osteoarthritis is efficacious for relieving the signs and symptoms of a torn meniscus but not for osteoarthritis. Likewise, in young and active patients, clinical outcomes show improvement after realignment osteotomy for single-compartment osteoarthritis. Unicondylar knee replacement is not indicated for tricompartmental disease of the knee.

DISCUSSION: This patient's history and physical findings are concerning for deep infection. Inflammatory markers, including ESR and CRP, should be obtained first. If the levels are elevated, knee aspiration should be performed for the synovial cell count and culture. A bone scan is not indicated in an initial investigation for deep infection; it is rarely helpful and is not cost effective. CT to assess implant rotation is an appropriate investigation for knee pain when the clinical scenario is not suspicious for a deep infection and when infection has been excluded.

The patient has a displaced femoral neck fracture. Although the treatment remains controversial, most clinicians advocate either a closed or open reduction in younger active patients. Achieving an anatomic reduction is necessary to avoid loss of reduction, nonunion, or osteonecrosis. Parallel multiple screws or pins are the most common method of internal fixation.

Both CRP and ESR results are negative, so aspiration of the hip to rule out periprosthetic hip infection is not recommended. The pain may be the result of a noninfectious process such as polyethylene wear with lysis or a muscle strain. A bone scan is of limited value, as is any further bloodwork. If the symptoms continue, further imaging may be of value.Cryotherapy has been demonstrated to achieve what effect after total knee replacement?Decreased transfusion requirementImproved pain, swelling, and analgesiaImproved range of motion at the time of dischargeBetter long-term knee range of motionCorrent answer: 3In a meta-analysis of randomized controlled trials on the efficacy of cryotherapy after total knee arthroplasty, patients treated with cryotherapy had less blood loss but no difference in transfusion requirements. There was better range of motion at the time of discharge from the hospital. There was no improvement in pain, swelling, or analgesia requirements. Patients treated with cryotherapy did not have better long-term range of motion.Compared to retention of the native patella in primary total knee arthroplasty, routine patella resurfacing is associated withno patellar complications.an increased occurrence of anterior knee pain.a decreased patellar fracture rate.a decreased risk for revision surgery.Despite concerns regarding fracture, osteonecrosis, and patellar clunk, the routine retention of the native patella during primary total knee replacement is associated with a 20% to 30% increased revision risk in large joint registries. In addition, the retention of the native patella results in a 5.7% revision surgery rate in patients with anterior knee pain.What clinical outcome is associated with total hip replacements that have metal-metal bearings (compared to total hip replacements with metal-polyethylene bearings)?Soft-tissue sarcomasSimilar revision rates at 5 yearsIncreased nephrotoxicityPseudotumorsPatients with metal-metal total hip bearings have higher levels of cobalt and chromium in the bloodstream, but systemic migration of wear debris from total hip bearings is also common to total hip arthroplasties with polyethylene bearings. There is no direct evidence that patients with metal-metal total hip arthroplasties experience a higher incidence of cancer. Chromosome abnormalities have been detected in patients with metal-metal hip bearings, and the clinical consequences of this finding remain unknown. Also, pseudotumors can form around the periprosthetic joint space in response to localized metal ion debris and the host inflammatory response, although these tumors are not specific for failed metal-metal total hip arthroplasties. Metal-on-metal hip replacements have higher revision rates compared to conventional hip replacements in multiple registry studies. Although metal-on-metal articulations have not been shown to cause renal failure, they are not recommended in patients with chronic renal insufficiency.A 55-year-old man with unilateral osteoarthritis of the hip underwent a total hip arthroplasty using cementless fixation. The acetabular cup was 52 mm and the femoral head was 28 mm and made of cobalt-chromium alloy. The bearing surface was made of annealed highly cross-linked polyethylene, with an estimated thickness of 6.5 mm. What should the orthopaedic surgeon tell the patient regarding wear of the bearing surface?A highly cross-linked polyethylene bearing has superior wear characteristics compared to a conventional polyethylene bearing.A highly cross-linked polyethylene bearing has similar wear characteristics compared to a conventional polyethylene bearing.The incidence of osteolysis is expected to be higher with highly cross-linked polyethylene than with conventional polyethylene.The volumetric wear rate would be lower if a 36-mm femoral head were used.In a prospective, randomized clinical trial of 100 patients undergoing cementless total hip arthroplasties, the investigators compared highly crossed-linked polyethylene to conventional polyethylene. All of the femoral heads were 28 mm. The mean follow-up was 6.8 years. The mean head penetration was 0.003 mm/year for the highly cross-linked polyethylene group in comparison to 0.051 mm/year for the conventional polyethylene group (P =.006). The improved wear is seen with larger-diameter heads as well. The volumetric wear rate of highly cross-linked polyethylene is equivalent to slightly higher with a larger head than a 28-mm head. Incidence of periarticular osteolysis is lower with highly cross-linked polyethylene.A 49-year-old active man has groin pain 3 years after undergoing an uneventful total hip replacement using a cobalt-chrome femoral head articulating against a cobalt-chrome acetabular insert. The pain intensifies with activity and travels down his thigh. Examination and radiographic evaluation are not particularly helpful; there is no evidence of spinal or vascular disease. What is the next step in the evaluation of this patient?A 3-phase bone scanMeasurement of synovial metal ions levelsErythrocyte sedimentation rate (ESR), C-reactive protein (CRP), andpossible hip aspirationBearing exchange to a metal-polyethylene combinationCorrent answer: 3ESR, CRP, and possible hip aspiration is the most logical next step even though at some point, bearing exchange may emerge as the ultimate treatment for a metal-metal adverse reaction in this patient. But the initial workup of a patient with a painful total hip that was otherwise functioning well must include the differential diagnosis of infection, which must be excluded with an appropriate laboratory workup, clinical history, and hip aspiration. The latter study may also help to diagnose a reaction to the metal bearing; cobalt and chromium levels in the aspirate can be investigated, and the color and quantity of the aspirate can be examined along with the cell count. Serum levels of metal ions at this stage could be both helpful and difficult to interpret.Figures A and B are the radiographs of a 25-year-old woman whose right knee pain has progressed during the last several years to pain with any activity and pain at night. What is the most appropriate treatment?Proximal tibial osteotomyDistal femoral osteotomyLateral unicompartmental arthroplastyTotal knee arthroplastyArthroscopic partial lateral meniscectomyCorrent answer: 2This patient is a good candidate for a joint-preserving procedure. Her symptoms and radiographic findings reveal valgus malalignment of the knee with narrowing of the lateral joint space. The alignment can be corrected with a varus-producing distal osteotomy. Most patients do not proceed to knee arthroplasty for at least 10 years after this procedure. Osteotomy is preferred over partial or total knee arthroplasty because of the patient's young age.Varus proximal tibial osteotomy would result in joint line obliquity.An orthopaedic surgeon noticed a displaced calcar fracture during stem insertion when performing total hip arthroplasty using cementless fixation. What is the most appropriate course of action?Intraoperative exploration to determine the extent of the fractureUse of a longer stem without fixation of the calcar fractureComplete insertion of the stem and measures to protect the patient against full weight bearing for 4 weeksRemoval of the stem, internal fixation of the fracture, and definitive reconstruction at a later stage after the fracture has healedCalcar fractures can occur with both cemented and cementless stem fixation during surgery. The distal extent of the fracture must be identified either by direct visualization or intraoperative radiograph prior to fixation or implantation of the femoral component. The recommended treatment is to fix the calcar fracture with cerclage wires/cables to restore the mechanical stability of the femoral metaphysis. The same stem can be inserted successfully. The majority of these fractures unite without adverse stem fixation problems.A 48-year-old woman had an 8-month history of spontaneous onset of left medial knee pain. She was otherwise healthy with an unremarkable past medical history. Prior to the onset of knee pain, she jogged, played tennis, and golfed regularly. She wished to remain active. Examination showed a fit woman with a BMI of 26, a stable leftknee with full range of motion, and some mild medial joint line tenderness. Radiograph results were normal. An MRI scan showed diffuse grade 3 and a focal area of grade 4 chondromalacia on the medial femoral condyle. The medial meniscus had a degenerative signal but no tear. The remainder of the knee showed no additional pathology. What is the most appropriate initial treatment?Lateral heel wedgeLow-impact aerobic exercisesGlucosamine 1500 mg/day and chondroitin sulfate 800 mg/dayArthroscopic debridement and microfracture of the focal area of grade 4 chondromalacia to reduce risk for progressionThis patient has early medial compartmental osteoarthritis of her knee. According to the 2008 AAOS Clinical Practice Guideline,Treatment of Osteoarthritis of the Knee (Non-Arthroplasty), there is Level 1 evidence and an "A" recommendation for the use of low-impact aerobic exercises. The guideline also has "A" recommendations with Level 1 evidence indicating that glucosamine and chondroitin should not be prescribed and that arthroscopic debridement not be performed in the absence of symptoms of a meniscal tear or loose body. Lateral heal wedge is not appropriate; the AAOS guideline provides a "B" recommendation with Level 2 evidence indicating that a lateral heal wedge not be prescribed.Figure 36 is the postoperative photograph of a patient who underwent a total knee arthroplasty 10 days after surgery. Knee aspiration suggests aStreptococcusinfection.Stop physical therapy and institute oral antibiotics.Stop physical therapy and institute intravenous (IV) antibiotics.Open irrigation and debridement, polyethylene spacer exchange, and IV antibioticsRemove components and insert an antibiotic spacer.An acute postoperative infection during the first 2 to 4 weeks should be treated with a return to the operating room for open irrigation and debridement of the wound. Polyethylene spacer exchange aides in washing out the entire knee joint. IV antibiotics are also indicated in this situation. To address persistent wound drainage, there is no role for oral or IV antibiotics alone. Removal of the arthroplasty components is recommended for infections after the initial 2- to 4-week postoperative period. However, several recent publications demonstrate a failure rate higher than 50% when the organism is a methicillin-resistantStaphylococcus aureus. Six weeks after surgery, this scenario is no longer considered an acute postoperative infection, and most authors recommend a 2-stage protocol with removal of components and placement of an antibiotic-impregnated cement spacer and 4 to 6 weeks of IV antibiotics.What is the difference in outcome when comparing high tibial osteotomy (HTO) to total knee arthroplasty (TKA)?TKA has a longer recovery period than HTO.HTO provides more complete pain relief than TKA.HTO is more reliable in older patients than TKA.HTO outcomes among thin, active, young patients who undergo this procedure approach outcomes associated with TKA.The ideal candidate for HTO is a thin, active person with a stable knee, unicompartmental knee symptoms, and age younger than 60. TKA offers a shorter recovery period and more complete pain relief than HTO. TKA is believed to be more reliable than HTO for patients older than age 60.Figure 39 is a radiograph of a 72-year-old man who underwent an open reduction and internal fixation of a right femoral neck fracture. After 3 months he started to develop pain, and during the next 8 months he complained of progressive pain and shortening of the hip. What is the most appropriate treatment?GirdlestoneTotal hip replacementHardware removalHardware removal with revision open reductions and internal fixationCorrent answer: 2Even though a relatively short amount of time has passed since the index surgery, this patient has developed significant osteonecrosis that has caused collapse of the bony structures and the hardware prominent. Total hip replacement gives the most efficient pain relief. Hardware removal with or without re-reduction does not provide reliable pain relief. A girdlestone does not allow the patient to function.Figure 40 is the radiograph of a 68-year-old woman who has right knee pain that is limiting her activity and severe preoperative valgus deformity. During total knee arthroplasty, what pathologic features are typically encountered?Lateral femoral hypoplasiaInternal rotation of the tibia relative to the femurMedial patella trackingTight medial collateral ligamentCorrent answer: 1In patients with severe valgus deformity, problems frequently encountered include loose or attenuated medial collateral ligament, tight lateral retinaculum and lateral ligamentous structures (lateral collateral, posterolateral corner), atrophic lateral femoral condyle, lateral patella tracking, and external rotation of the tibia relative to the femur. The hypoplastic lateral condyle can cause internal rotation of the anteroposterior cutting block if the posterior condyler line is used for rotational alignment. The medial soft tissues are typically attenuated and stretched.A 59-year-old active woman underwent elective total hip replacement using a posterior approach. She had minimal pain and was discharged to home 2 days after surgery. Four weeks later she dislocated her hip while shaving her legs. She underwent a closed reduction in the emergency department. Postreduction radiographs show a reduced hip with well-fixed components in satisfactory alignment. What is the most appropriate management of this condition from this point forward?Observation and patient education regarding hip dislocation precautionsRevision to a larger-diameter femoral headRevision to a constrained acetabular componentApplication of a hip orthosis for 3 monthsCorrent answer: 1First-time early dislocations are often successfully treated without revision surgery, especially when there is no component malalignment. In this clinical scenario, it appears the patient would benefit from better education about dislocation precautions. Hip orthoses are of questionable benefit unless the patient is cognitively impaired. Revision surgery can be successful, but is usually reserved for patients with recurrent dislocations.Patellar pain, subluxation, or dislocation after total knee arthroplasty can result from which of the following component orientations?Internal rotation of the tibial componentLateralization of the tibial componentLateralization of the femoral componentExternal rotation of the femoral componentCorrent answer: 1Internal rotation of the components of a total knee arthroplasty, both the tibial and femoral components, can lead to symptoms ranging from patellar pain to dislocation. Most researchers agree that proper external rotation of the femoral component is parallel or nearly so to the femoral epicondylar axis with the knee in the 90-degree flexed position. Proper rotational positioning of the tibial component places the midportion of the tibial component rotationally aligned within the medial one-third of the tibial tubercle. Internal rotation of the tibial component causes relative lateralization of the tibial tubercle and the extensor mechanism. Lateralization of the femoral component moves the trochlear groove laterally. Lateralization of the tibial component moves the tibial tubercle medially, which may be beneficial to patellar tracking.How does the risk for periprosthetic infection after total knee arthroplasty compare to risk for infection after total hip arthroplasty?Higher in primary arthroplastyLower in primary arthroplastyLower in revision arthroplastyEquivalent in both primary and revision arthroplastyCorrent answer: 1Risk for periprosthetic infection is higher in the knee (1%-2%) than it is in the hip (0.3%-1.3%). The risk for infection is higher after revision joint replacement surgery compared to primary joint replacement surgery.Osteoarthritis is not associated with a higher risk for periprosthetic infection, but certain inflammatory conditions such as rheumatoid arthritis and psoriatic arthritis place patients at higher risk for postoperative infection.What factor is associated with a higher risk for dislocation after total hip arthroplasty?Male genderPrevious hip surgeryA direct lateral surgical approachMetal-on-metal bearing surfacesCorrent answer: 2Dislocation after total hip arthroplasty is a multifactorial problem. Numerous risk factors may act independently or cumulatively to increase risk for this complication. Previous hip surgery of any kind is associated with a twofold increased risk for dislocation. Other risk factors include female gender, impaired mental status, inflammatory arthritis, and older age. Numerous studies have shown a lower dislocation rate with a direct lateral approach, although surgical techniques such as capsular repair have significantly lowered the incidence of dislocation after using the posterior approach. Metal-on-metal bearings have been associated with other complications such as adverse tissue reactions but are often used with larger-diameter bearings, which pose lower risk for dislocation.What surgical technique has been associated with increased risk for recurrent dislocation after revision total hip arthroplasty?Posterior capsulorrhaphyUse of a jumbo cupUse of a lateralized linerUse of a larger femoral head diameterCorrent answer: 2When addressing recurrent dislocation after total hip arthroplasty, surgical considerations that must be addressed include approach, soft-tissue tension, component positioning, impingement, head size, and acetabular liner profile. These considerations most often involve tensioning or augmentation of soft tissues, as in capsulorrhaphy or trochanteric advancement; correction of malpositioned components; use of larger femoral head sizes that increase motion before impingement; improving the head-to-neck ratio; and increasing femoral offset. The use of a larger-diameter acetabular component may lead to soft-tissue overgrowth around the liner, causing impingement and increasing the risk for recurrent dislocation.A 67-year-old active man returns for routine follow up 12 years after hip replacement. He has no hip pain. Radiographs revealed awell-circumscribed osteolytic lesion around a single acetabular screw. All hip components were perfectly positioned. Six months later, comparison radiographs show an increase in the size of the osteolytic lesion. A CT scan shows a well-described lesion that is 3 cm at its largest diameter and is localized around 1 screw hole with an eccentric femoral head. What treatment is appropriate, assuming well-fixed cementless total hip components exist?Revision of the polyethylene liner, removal of the screw, and debridement of the osteolytic lesion with or without bone graftingRevision of the acetabular component to a newer design without screwsRemoval of the screw, revision of the polyethylene liner, and stem cell injection into the lytic lesionRemoval of the offending screw from the metal socket and placement of a new polyethylene liner in the existing socketWith a well-fixed acetabular metal shell and a localized osteolytic lesion, good outcomes can be expected with liner revision in this clinical scenario with retention of the metal socket, assuming no damage to the components or other unexpected findings during revision surgery. Here, complete cup revision is not warranted considering the appropriate implant position. Beaule and associates reviewed 83 consecutive patients (90 hips) in which a well-fixed acetabular component was retained in clinical scenarios such as the one described; no hip showed recurrence or expansion of periacetabular osteolytic lesions. If the metal cup is unstable, or if the osteolytic lesion is not amenable to debridement through the screw hole, acetabular component revision may be indicated.What has been identified as a risk factor for total knee arthroplasty failure after previous high tibial osteotomy?Body mass index higher than 35Female genderPreoperative stiffnessAdvanced ageIncreased weight, male gender, young age at the time of total knee arthroplasty, laxity, and limb malalignment preoperatively have been identifiedas risk factors for early failure for total knee arthroplasty following high tibial osteotomy.You are caring for an 18-year-old boy with severe hip arthritis and pain from a missed slipped capital femoral epiphysis. You decide that a hip arthrodesis is the best treatment option. What is the optimum position for a hip arthrodesis to maximize function and prevent complications?0° external rotation, 0° adduction, 0° hip flexion5° external rotation, 5° adduction, 20° hip flexion5° external rotation, 15° abduction, 5° hip flexion15° external rotation, 0° adduction, 20° hip flexion15° external rotation, 15° abduction, 5° hip flexionHip arthrodesis is a salvage procedure for patients with hip arthritis without ipsilateral knee, contralateral hip, or lumbar spine pathology. The optimal position for hip arthrodesis is 5 degrees of adduction, 5-10 degrees of external rotation, and 20-35 degrees of hip flexion.In their review, Beaule et al. discuss the current indications and techniques regarding hip arthrodesis including appropriate leg position, surgical techniques, methods to optimize function, and later conversion to hip arthroplasty.Callaghan et al. evaluated the long term efficacy (20-25 yrs) of hip arthrodesis. They found the onset of ipsilateral knee, contralateral hip, or lumbar spine pathology usually began 20 years after the arthrodesis. Of their patients, they found a 15% rate of conversion to hip arthroplasty by 20 years.What limits indications for the use of constrained liners?Association with periprosthetic fractureTechnical difficulty associated with insertionHigh costs associated with their useHigh failure rates associated with their useCorrent answer: 4Because of reports of relatively high failure rates associated with constrained liners, indications are limited to continued instability after appropriate component position or deficient abductor mechanism and instability. Neither cost nor technical insertion issues are relevant with regard to indications for use. Periprosthetic fractures are not associated with constrained liner usage.What serum inflammatory marker has the highest correlation with periprosthetic joint infection?C-reactive proteinSerum white blood cell countErythrocyte sedimentation rateInterleukin 6 (IL-6)Although CRP and ESR can be elevated in the setting of infection, IL-6 has been shown to have the highest correlation with infection. Serum white blood cell count has been shown to be ineffective in correlating with periprosthetic joint infection.A 68-year-old man reports hip pain 15 years after successful cementless total hip arthroplasty. Radiographs show 3 mm of linear wear of the modular acetabular liner and a retro-acetabular osteolytic lesion. Both the titanium femoral and acetabular components appear to be well fixed. The orthopaedic surgeon recommends revision of the acetabular liner and femoral head. This patient is at increased risk fordislocation.periprosthetic fracture.infection.progressive osteolysis.Isolated acetabular liner revision is frequently performed in cases of liner wear and periprosthetic osteolysis in the absence of acetabular component loosening. Many reports have documented an increased incidence of dislocation following this type of revision surgery. This dislocation rate can be reduced by using a larger-diameter femoral head at the time of revision. If theacetabular component is loose or malpositioned, it should be revised. If the locking mechanism is damaged, then a replacement liner may be cemented into the well-fixed shell. Numerous studies have shown that many osteolytic lesions will reduce in size or heal without bone grafting, and removal of the source of wear debris will arrest the progression of osteolysis. The risk for periprosthetic fracture and infection are lower than risk for dislocation in this setting.A 61-year-old man with a body mass index of 31 had a 6-month gradual onset of right medial knee pain. Examination revealed a small effusion, stable ligaments, a normally tracking patella, and mild medial joint line tenderness. Standing radiographs show mild medial joint space narrowing. Effective treatment at this stage of early medial compartmental osteoarthritis includesglucosamine 1500 mg/day and chondroitin sulfate 800 mg/day.weight loss through dietary management and low-impact aerobic exercises.arthroscopic debridement and lavage.a valgus-directing brace.According to the 2008 AAOS Clinical Practice Guideline,Treatment of Osteoarthritis of the Knee (Non-Arthroplasty), Level 1 evidence confirms that weight loss and exercise benefit patients with knee osteoarthritis. The other responses have either inclusive evidence (a valgus-directing brace) or no evidence to support their use (glucosamine 1500 mg/day and chondroitin sulfate 800 mg/day and arthroscopic debridement and lavage).The range of knee mobility after total knee replacement is multifactorial and dependent upon implant design, surgical implantation accuracy, and patient-specific variables. What total knee implant design is associated with the most knee flexion after total knee replacement?Highly conforming articular surface geometryHigher-flexion femoral component design manufactured to allow the most knee flexionPosterior cruciate-stabilized implant, with or without a higher flexionmanufacturing modificationPosterior cruciate-retaining design with a mobile bearing, custom implanted based on CT scan dataA posterior cruciate-stabilized implant has the best support in the literature in terms of the most favorable range of motion after knee arthroplasty, regardless of whether the femoral component is designed with a higher flexion variation. The higher flexion design is a manufacturing variation that is intended to increase motion by clearing the posterior condyles in flexion.Although the knee may not gain more flexion, this design allows for more safety in deep flexion. The long-term outcomes of increased stresses on the polyethylene are not known, however. By itself, a higher-flexion design does not lead to increased knee mobility. The effects of mobile bearings, custom CT scan-based knee implantation, and highly conforming designs on ultimate knee range of motion are uncertain.In total knee arthroplasty, in vitro testing has shown that crosslinking can diminish the rate of polyethylene wear by 30% to 80%.What other change in material properties is possible when polyethylene is highly cross-linked?Increased ductilityIncreased wettabilityDiminished fatigue strengthDecreased resistance to abrasive wearCorrent answer: 3The most important concern regarding highly cross-linked polyethylene relates to decreased mechanical properties. Cross-linking results in reduced ductility, tensile strength, and fatigue crack propagation resistance. These problems have not been identified as causing implant failure in most recent clinical trials, but remain the most important mechanical issues associated with current material processing methods.What factor is associated with a high risk for developing pseudotumors after metal-on-metal hip resurfacing?Large-diameter componentsAge 40 or older for menAge 40 or younger for womenDiagnosis of primary osteoarthritisCorrent answer: 3The recent experience of a large clinical cohort revealed the most likely risk factors as female gender, age younger than 40, small components, and the diagnosis of hip dysplasia causing osteoarthritis. Failure was least likely among men and procedures involving larger components. These data have prompted some authors to caution against use in women and to primarily target candidates who are men younger than age 50. Small components may be more prone to failure because of malpositioning and edge loading, which have been noted to be more common in dysplasia cases.A 70-year-old man is scheduled to undergo bearing surface revision for wear and osteolysis 10 years after cementless total hip arthroplasty. The femoral head is 28 mm alumina-oxide ceramic material. The components are in good position, and there is no evidence of fixation loosening of either component by radiograph or preoperative bone scan. What outcome is associated with isolated polyethylene exchange?Reduced risk for future wear and osteolysis with a larger femoral headReduced risk for future wear and osteolysis with a cobalt chrome femoral headSimilar risk for dislocation compared to primary total hip arthroplastyIncreased risk for dislocation compared to primary total hip arthroplastyCorrent answer: 4The major complication associated with polyethylene exchange is postoperative dislocation. Maloney and associates noted a dislocation rate of 11% in a study of 35 hips after such revision. Boucher and associates reported a 25% rate of dislocation in a study of 25 patients. Larger femoral heads result in higher volumetric wear in contrast to smaller-diameter heads. Stem revision is not indicated because there is no fixation loosening. Moreover, stem biomaterial has no effect on polyethylene wear.A healthy, active 68-year-old woman had a total hip arthroplasty 3 months ago. She has been to the emergency department with a posterior dislocation 3 times during the last 2 months. Plain radiographs and a CT scan confirm that the acetabular component is oriented in 5 degrees of retroversion and 55 degrees of abduction.What is the most appropriate treatment?Revision of the femoral and acetabular componentsMaximizing head-neck ratio and increasing head lengthAcetabular component revisionClosed reduction with an abduction brace and reinforcement of hip precautionsAcetabular malposition can lead to recurrent instability. When this cause is confirmed, reorientation of the component can lead to successful revision surgery. Revision of the femoral component may not be necessary if the acetabular component is repositioned. Increasing length and maximizing head-neck ratio cannot make up for component malposition. There is no role for nonsurgical treatment in the setting of recurrent instability with component malposition in an active, healthy patient.A 55-year-old woman with history of HIV infection is scheduled for revision total knee arthroplasty to address instability. The index surgery was done 3 years ago. What is the white blood cell (WBC) count threshold in the synovial fluid for an infection diagnosis?

THA is the best long term solution for displaced femoral neck fractures (FNF) in active elderly patients.The aims of surgery for FNF in elderly patients are immediate pain relief, rapid mobilization, and low complications and revision. THA has best pain relief, fewer reoperations, best survivorship and is most cost-effective but has longer operative/anesthetic time, blood loss, higher infection rate, and potential instability compared with HA.Healy and Iorio examined the optimal treatment for elderly FNF. They compared internal fixation (120 patients) with arthroplasty (HA, 43 patients; THA, 23 patients). There was no different in reoperation or mortality rates between the 2 groups, but arthroplasty was more cost effective, had independent living, and longer interval to reoperation/death. THA had less pain, better function, and lower rates of reoperation than HA, and was most cost-effective. They concluded that THA was the best treatment.Yu et al. performed a meta-analysis of randomized controlled trials to determine whether THA or hemiarthroplasty (HA) was superior. They found that THA had lower risk of reoperation (RR = 0.53), higher risk of dislocation (RR = 1.99), andhigher functional scores at 1 and 4 years. There was no difference in mortality, infection and complication rates.Figure A shows a displaced left femoral neck fracture. Incorrect Answers:

Polyethylene wear debris can result in significant synovitis and subsequent cloudy appearing synovial fluid. Typically, laboratory studies show a WBC of less than 30,000/mm3 and no left shift. Cytologic examination can reveal intra-articular polyethylene particles.

The patient has an early prosthesis infection as a result of hematogenous seeding from dental surgery. Irrigation and debridement with polyethylene exchange and IV antibiotics have been successful in early postoperative infections; it is less likely to be effective for a late hematogenous infection. Immediate total component exchange also may be effective, but it should be reserved for failure of irrigation and debridement.

The patient is experiencing an adverse local tissue reaction (ALTR) or ALVAL, characterized by a pseudotumor in a metal-on-polyethylene THA. Because the bearing surface is non-metal-on-metal, the source of the metal ions is the modular head-neck junction (trunnion). Mechanically assisted crevice corrosion (MACC), or trunnionosis, is exacerbated by the use of large-diameter cobalt-chromium heads on titanium stems, leading to metal debris generation and subsequent pseudotumor formation.

The classic Kozinn and Scott criteria for unicompartmental knee arthroplasty include absolute contraindications such as inflammatory arthritis (e.g., rheumatoid arthritis), tricompartmental disease, fixed varus deformity >15 degrees, fixed valgus >20 degrees, and flexion contracture >15 degrees. While weight >82kg and age were historically considered relative contraindications, modern literature has relaxed these, but inflammatory arthritis remains an absolute contraindication due to global joint involvement.

A retroverted acetabular cup promotes anterior femoroacetabular impingement when the hip is in flexion and internal rotation. This impingement acts as a fulcrum, levering the femoral head out posteriorly.

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which occurs with a steeply positioned acetabular cup (inclination > 50 degrees) or excessive anteversion. This leads to disruption of fluid-film lubrication and localized stripe wear.

A tight extension gap with a balanced flexion gap indicates an asymmetric extension space. The appropriate management includes releasing the posterior capsule or resecting more distal femur, which selectively increases the extension gap without affecting flexion.

Squeaking in ceramic-on-ceramic total hip arthroplasties is strongly correlated with edge loading, typically secondary to component malposition (such as excessive cup anteversion or inclination). Edge loading leads to localized stripe wear on the ceramic head, generating the acoustic phenomenon.

A knee that is tight in flexion but balanced in extension has an isolated tight flexion gap. Downsizing the femoral component decreases the posterior condylar offset, thereby increasing the flexion gap without altering the extension gap.

Adverse local tissue reactions (ALTR) in metal-on-metal implants are characterized histologically by Aseptic Lymphocytic Vasculitis-Associated Lesions (ALVAL). This represents a delayed-type hypersensitivity reaction to metal ions (cobalt and chromium).

The surgeon in this case is faced with a common scenario at the time of revision total knee arthroplasty and the tendency is to elevate the joint line. Elevation of the joint line is associated with deleterious effects including anterior knee pain, restricted knee flexion, and instability. The error that has been made is resting the femoral component on the bone that is left behind after removal of the prior component; this typically leads to a femoral component that is too small (leading to an enlarged flexion gap) and proximal to where it should be (enlarging the extension gap). Although the flexion and extension gaps are equivalent, joint line elevation has occurred. To correct this problem, the femoral component size should be increased or offset posteriorly (to decrease the size of the flexion gap) and distal femoral augments should be used to decrease the size of the extension gap and restore the joint line to the appropriate level.

This complication is best addressed with either a single-stage or two-stage total knee arthroplasty. A recent report suggests that a single-stage arthroplasty can be effective, although many surgeons would perform a two-stage procedure with an articulating or static spacer. Arthroscopic debridement would be ineffective, especially given 4 weeks of symptoms. Resection arthroplasty without a spacer would leave an unstable and poorly functioning extremity. Knee fusion should be used as a salvage procedure.

Femoral shortening osteotomy for a Crowe type IV hip dislocation has been shown to provide superior results with minimal complications. Cementless fixation of the stem allows for modular implants that greatly simplify the reconstruction.