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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 111 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2201

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old patient with rheumatoid arthritis has had pain and instability of the elbow following total elbow replacement 2 years ago. A complete work-up, including aspiration and cultures, is negative. Figures 9a and 9b show the AP and lateral radiographs. Treatment should consist of

. orthotic stabilization.
. removal of the components with resection arthroplasty.
. revision total elbow arthroplasty with an unconstrained prosthesis and ulnar allograft.
. revision total elbow arthroplasty with a semiconstrained long-stemmed ulnar prosthesis.
. elbow arthrodesis with bone grafting.

Correct Answer & Explanation

. revision total elbow arthroplasty with a semiconstrained long-stemmed ulnar prosthesis.

Explanation

The patient has aseptic loosening of the original semiconstrained prosthesis and significant proximal ulnar bone destruction; therefore, the treatment of choice is revision arthroplasty using a semiconstrained design. Although orthotic stabilization could be used, it will not provide long-term pain relief. Resection arthroplasty after removal of the components may lead to painful instability. Elbow arthrodesis would be difficult with the bone stock loss and is not considered the best option. Two main contraindications to the use of an unconstrained prosthesis are significant bone loss and previous use of a hinged or semiconstrained prosthesis. An ulnar allograft could be combined with the use of a semiconstrained long-stemmed ulnar prosthesis as a treatment modification. Ewald FC, Simmons ED Jr, Sullivan JA, et al: Capitellocondylar total elbow replacement in rheumatoid arthritis: Long-term results. J Bone Joint Surg Am 1993;75:498-507.

Question 2202

Topic: 3. Adult Reconstruction (Hip & Knee)

During total knee arthroplasty, the patella is noted to subluxate laterally despite a lateral retinacular release. Which of the following methods is most likely to improve patellar stability?

. Slight external rotation of the tibial component
. Slight internal rotation of the femoral component
. Slight anterior translation of the tibial component
. Use of a fixed-bearing knee as opposed to a mobile-bearing knee
. Use of a a thicker patellar component

Correct Answer & Explanation

. Slight external rotation of the tibial component

Explanation

Slight external rotation of the tibial component will cause a net medialization of the tibial tubercle when the knee is articulated. This will help centralize the extensor mechanism over the trochlear groove and minimize the tendency for lateral subluxation. Internal rotation of the femoral component increases the risk of patellar instability. Anterior translation of the tibial component moves the patellar tendon insertion posteriorly, and may increase force on the patella but should not substantially alter patellar tracking. Clinical studies have shown no patellofemoral benefits to the use of fixed- or mobile-bearing designs. Thicker patellar components will not improve tracking, and may compound the problem. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 207, 323-337 Pagnano MW, Trousdale RT, Stuart MJ, et al: Rotating platform knees did not improve patellar tracking: A prospective, randomized study of 240 primary total knee arthroplasties. Clin Orthop 2004;428:221-227.

Question 2203

Topic: 3. Adult Reconstruction (Hip & Knee)

A 2-year-old girl was born with the toe deformity shown in Figure 2. She has difficulty wearing shoes despite having adequate room in the toe box. Management at this time should consist of

Pediatrics 2001 Practice Questions: Set 1 (Solved) - Figure 2

. stretching exercises, followed by taping of the toes in a derotational maneuver.
. lengthening of the extensor digitorum longus tendon of the second toe and release of the metatarsophalangeal joint dorsal capsule.
. resection arthroplasty of the proximal interphalangeal joint of the third toe, with release of the volar plate.
. tenotomy of the flexor digitorum longus and brevis of the third toe.
. a Girdlestone-Taylor transfer of the flexor digitorum longus to the extensor digitorum longus of the third toe.

Correct Answer & Explanation

. tenotomy of the flexor digitorum longus and brevis of the third toe.

Explanation

The patient has a congenital curly toe deformity of the third toe, and tenotomy of the toe flexors is highly effective for this problem. Stretching and taping are ineffective for this deformity. The position of the second toe is secondary; therefore, procedures on that toe are unnecessary and ineffective. The flexor to extensor transfer is a more complicated procedure that produces negligible results, or may even worsen the deformity. Resection arthroplasty is contraindicated because it causes abnormal growth of the toes. Hamer AJ, Stanley D, Smith TW: Surgery for curly toe deformity: A double-blind, randomized, prospective trial. J Bone Joint Surg Br 1993;75:662-663. Ross ER, Menelaus MB: Open flexor tenotomy for hammer toes and curly toes in childhood. J Bone Joint Surg Br 1984;66:770-771.

Question 2204

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old patient undergoing revision total knee arthroplasty has bone loss throughout the knee at the time of revision. A distal femoral augment is used to restore the joint line. One month after surgery, the patient reports pain and is unable to ambulate. A lateral radiograph is shown in Figure 34. What is the most likely etiology of this problem?

Hip & Knee Reconstruction 2007 Practice Questions: Set 3 (Solved) - Figure 7

. Inadequate restoration of the joint line
. Patellar tendon rupture
. Excessive internal rotation of the tibial component
. Flexion gap instability
. Hyperextension of the femoral component

Correct Answer & Explanation

. Flexion gap instability

Explanation

Instability is a leading cause of failure following total knee arthroplasty. Instability can present as global instability, extension gap (varus/valgus) instability, or flexion gap (anterior/posterior) instability. Treatment options are numerous based on the exact pathology. The radiograph reveals anterior/posterior instability with dislocation consistent with flexion gap instability. A loose flexion gap can allow the femoral component to ride above the tibial cam post mechanism, resulting in dislocation. Distal femoral augments treat extension gap instability, whereas tibial augments can treat both flexion and extension gap instability. Posterior condyle augments at the distal femur can also be used to treat flexion gap instability. Flexion gap instability is further aggravated by extension mechanism incompetence. Note the excessively thin patella on the lateral radiograph. Pagnano MW, Hanssen AD, Lewallen DG, et al: Flexion instability after primary cruciate retaining total knee arthroplasty. Clin Orthop 1998;356:39-46. McAuley J, Engh GA, Ammeen DJ: Treatment of the unstable total knee arthroplasty. Inst Course Lect 2004;53:237-241.

Question 2205

Topic: 3. Adult Reconstruction (Hip & Knee)

What clinical parameter will most likely decrease the need for blood transfusion after total joint arthroplasty?

. Bilateral total joint replacement
. Rheumatoid arthritis
. Preoperative donation of autologous blood
. Age greater than 65 years
. Hemoglobin level of greater than 15 g/dL

Correct Answer & Explanation

. Hemoglobin level of greater than 15 g/dL

Explanation

Bilateral joint replacement, chronic disease, and preoperative autologous donation all increase the risk of needing blood. Young patients and a high hemoglobin level (greater than 15 g/dL) are considered clinical parameters that decrease the risk for requiring allogenic blood. Bierbaum BE, Callaghan JJ, Galante JO, Rubash HE, Tooms RE, Welch RB: An analysis of blood management in patients having a total hip or knee arthroplasty. J Bone Joint Surg Am 1999;81:2-10.

Question 2206

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 12 shows the radiograph of a 55-year-old man who has severe, painful osteoarthritis of the left hip and is scheduled to undergo a left total hip arthroplasty. History reveals that he underwent a right total hip arthroplasty 5 years ago that remains pain-free. Based on the preoperative radiograph, the patient is at greatest risk for what complication?

Hip Board Review 2001: High-Yield MCQs (Set 2) - Figure 3

. Intraoperative fracture
. Deep vein thrombosis
. Limb-length discrepancy
. Sciatic nerve palsy
. Thigh pain

Correct Answer & Explanation

. Limb-length discrepancy

Explanation

The patient is at increased risk for limb-length discrepancy because the radiograph shows that the left leg is already longer than the right leg. To restore the proper biomechanics of the left hip, the left leg may have to be lengthened, further increasing the limb-length discrepancy. Intraoperative fracture, deep vein thrombosis, sciatic nerve palsy, and thigh pain are commonly associated with total hip arthroplasty, but the patient is not at increased risk for these complications.

Question 2207

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 53a shows the AP radiograph of a 70-year-old patient who is scheduled to undergo unicompartmental knee arthroplasty. Figure 53b shows the immediate postoperative radiograph, and the radiograph shown in Figure 53c, obtained 6 months after surgery, shows a medial tibial plateau fracture. The etiology of the fracture is best related to

. marked osteoporosis.
. reduced contact area of a unicompartmental knee arthroplasty for load transmission.
. excessive medial placement of the tibial component of the unicompartmental knee arthroplasty.
. multiple drill holes that violate the medial cortex.
. osteonecrosis of the medial tibial plateau.

Correct Answer & Explanation

. multiple drill holes that violate the medial cortex.

Explanation

While all of the above may contribute to the etiology of a tibial plateau fracture following unicompartmental knee arthroplasty, the recent literature has clearly noted that pin placement for fixation of tibial resection guides is the most critical factor associated with a tibial plateau fracture following unicompartmental knee arthroplasty. Vince and Cyran suggest that fractures associated with unicompartmental knee arthroplasty might be avoidable by limiting the number and paying attention to the location of the pin holes that are created to secure the tibial resection guides. Brumby and associates suggest avoiding multiple guide pin holes in the proximal tibia for unicompartmental knee arthroplasty. They currently recommend the use of one centrally placed pin and an ankle clamp to stabilize the resection guide. Yang and associates note that a medial tibial plateau fracture in association with minimally invasive unicompartmental knee arthroplasty can be eliminated by avoiding fixation pins close to the medial tibial cortex. Brumby SA, Carrington R, Zayontz S, et al: Tibial plateau stress fracture: A complication of unicompartmental knee arthroplasty using 4 guide pinholes. J Arthroplasty 2003;18:809-812. Yang KY, Yeo SJ, Lo NN: Stress fracture of the medial tibial plateau after minimally invasive unicompartmental knee arthroplasty: A report of 2 cases. J Arthroplasty 2003;18:801-803.

Question 2208

Topic: 3. Adult Reconstruction (Hip & Knee)

When using the direct lateral (or Hardinge) approach for hip arthroplasty, three muscles are detached from the femur. In addition to the vastus lateralis, they include the

. iliopsoas and sartorius.
. piriformis and obturator internus.
. gluteus maximus and tensor fascia lata.
. gluteus minimus and rectus femoris.
. gluteus medius and gluteus minimus.

Correct Answer & Explanation

. gluteus medius and gluteus minimus.

Explanation

This approach is criticized for the episodic limp associated with the muscle detachment and reattachment. Classically, two thirds of the gluteus medius is detached as a sleeve with the vastus lateralis. This exposes the gluteus minimus and the ligament of Bigelow. These must also be detached to allow dislocation of the hip and osteotomy of the femoral neck. The rectus femoris lies medially and anteriorly and does not need to be addressed. The piriformis and obturator internus are exposed during the posterior approach. Neither the gluteus maximus nor tensor fascia lata attach to the anterior femur. The sartorius and iliopsoas are not exposed during this dissection. Hoppenfeld S, deBoer P (eds): Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, pp 333-335.

Question 2209

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 36 shows the radiograph of a patient who has hip pain and is unable to ambulate. What is the most appropriate management for this patient?

Hip & Knee Reconstruction 2007 Practice Questions: Set 3 (Solved) - Figure 9

. Bisphosphonates
. Protected weight bearing
. Open reduction and internal fixation
. Revision total hip arthroplasty
. Resection arthroplasty

Correct Answer & Explanation

. Revision total hip arthroplasty

Explanation

The patient has a periprosthetic fracture of the greater trochanter - Vancouver A. The reason for the fracture of the greater trochanter is the extensive periarticular osteolysis that has occurred as a result of polyethylene wear. The latter is demonstrated by eccentric seating of the large femoral head in the acetabulum. The most appropriate management is to reverse the osteolysis process, which involves exchange of the acetabular liner with or without revision of the other components depending on their fixation and position. The greater trochanter can also be fixed during revision surgery. Duncan CP, Masri BA: Fractures of the femur after hip replacement. Instr Course Lect 1995;44:293-304.

Question 2210

Topic: 3. Adult Reconstruction (Hip & Knee)

A 59-year-old man underwent interposition arthroplasty for osteoarthritis of the elbow 9 years ago. Over the past year the patient has had increasing pain and elbow instability. There is no clinical evidence of infection, and radiographs show no new bony process. What is the best option for this patient?

Upper Extremity Board Review 2008: High-Yield MCQs (Set 2) - Figure 26

. Bracing
. Physiotherapy
. Cortisone injection
. Conversion to total elbow arthroplasty
. Revision interposition arthroplasty

Correct Answer & Explanation

. Conversion to total elbow arthroplasty

Explanation

In a series reported by Blaine and associates, 12 patients were converted from interposition to total elbow arthroplasty. This procedure was successful in 10 out of 12 patients. Blaine TA, Adams R, Morrey BF: Total elbow arthroplasty after interposition arthroplasty for elbow arthritis. J Bone Joint Surg Am 2005;87;286-292.

Question 2211

Topic: Total Knee Arthroplasty (TKA)

A patient who underwent a high tibial osteotomy (HTO) is now scheduled to undergo total knee arthroplasty (TKA). When compared with a patient undergoing primary TKA without a prior HTO, the patient should be advised to expect a higher incidence of

. limited range of motion.
. patella complications.
. infection.
. loosening.
. tibia fracture.

Correct Answer & Explanation

. limited range of motion.

Explanation

Conversion TKA following a previous HTO can be successful; however, it is associated with poorer clinical results when compared with other primary TKAs. There is an increased likelihood of poor range of motion that is partially affected by patella infera created from the osteotomy. Patella infera also results in difficulty with surgical exposure. There has been no reported increase in the rate of infection, fracture, or loosening.

Question 2212

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 23 shows the radiograph of a 55-year-old man who underwent a total hip arthroplasty 5 years ago. Management should now consist of

Hip 2001 Practice Questions: Set 3 (Solved) - Figure 3

. an Ogden-type plate with screws and cerclage bands or cables.
. allograft bone plates fixed with cerclage cables and wires.
. skeletal traction for 8 weeks.
. revision of the femoral stem.
. resection arthroplasty.

Correct Answer & Explanation

. revision of the femoral stem.

Explanation

Because the radiograph shows that the femoral stem is loose within the femoral canal and there is a fracture in the distal cement mantle, the stem should be revised. The Ogden-type plate and the allograft bone plates will reconstruct the femur but will not restore stability to the stem. Similarly, traction may allow the femur to heal but will not restore stability to the femoral stem within the femur. Resection arthroplasty is considered a salvage option following failure of the other procedures. Lewallen DG, Berry DJ: Periprosthetic fracture of the femur after total hip arthroplasty: Treatment and results to date, in Cannon WD Jr (ed): Instructional Course Lectures 47. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 243-249.

Question 2213

Topic: Total Knee Arthroplasty (TKA)

A 17-year-old basketball player and pole vaulter who has had anterior knee pain for the past 18 months now reports a recent inability to jump. Based on the MRI scan shown in Figure 11, management should consist of

Sports Medicine Board Review 2007: High-Yield MCQs (Set 2) - Figure 8

. debridement and repair.
. cast immobilization.
. aggressive overload eccentric strengthening.
. ice massage and continued athletic participation.
. steroid injection.

Correct Answer & Explanation

. debridement and repair.

Explanation

The MRI scan reveals a partial patellar tendon rupture in conjunction with chronic patellar tendinitis. Mild and moderate patellar tendinitis may be treated nonsurgically with rest, stretching, strengthening, and anti-inflammatory drugs. Severe tendinopathy or extensor mechanism disruption is best treated surgically with tendon debridement and repair. Al-Duri ZA, Aichroth PM: Surgical aspects of patella tendonitis: Techniques and results. Am J Knee Surg 2001;14:43-50.

Question 2214

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures 22a and 22b show the radiographs of a patient who reports stiffness of the hip and associated pain. Management should consist of

. use of a cane for ambulation.
. diphosphonate therapy.
. physical therapy and indomethacin.
. surgical excision and radiation therapy.
. revision arthroplasty.

Correct Answer & Explanation

. surgical excision and radiation therapy.

Explanation

The patient has grade IV heterotopic ossification with the limb in an abnormal nonfunctional position. Treatment should consist of excision of the bone to restore hip motion and prophylaxis to prevent recurrent formation. The best time to excise the bone is controversial, with no conclusive evidence supporting early or late excision. Pellegrini VD Jr, Koniski AA, Gastel JA, Rubin P, Evarts CM: Prevention of heterotopic ossification with irradiation after total hip arthroplasty: Radiation therapy with a single dose of eight hundred centigray administered to a limited field. J Bone Joint Surg Am 1992;74:186-200.

Question 2215

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man who underwent cemented right total hip arthroplasty 6 years ago now reports acute pain for the past week. He denies any trauma, recent illnesses, or symptoms other than pain. Plain radiographs show possible loosening of the femoral component. A normal result from which of the following studies will most specifically rule out infection?

. Technetium Tc 99m bone scan
. Hip aspiration
. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
. WBC count
. MRI

Correct Answer & Explanation

. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)

Explanation

A patient with an infected total hip arthroplasty may lack the symptoms of fever, chills, redness, or increased warmth typical of septic arthritis. Sensitivity for ESR and CRP ranges from 61% to 96%, and specificity ranges from 85% to 100%. Technetium Tc 99m bone scans are costly and time-consuming and will not differentiate between septic and aseptic loosening. Hip aspiration has a false-positive rate of up to 15%, although it may be useful in this patient to further complement the clinical picture if the ESR and CRP are elevated. The WBC count is rarely elevated in infected total hip arthroplasty. MRI is expensive and is not indicated for the diagnosis; however, it can aid in identifying intrapelvic extension of a periprosthetic abscess. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 455-492.

Question 2216

Topic: Total Knee Arthroplasty (TKA)

Consider the theoretic articulation shown in Figure 11 as femoral and tibial components of a total knee prosthesis in which the components fit like a "roller in trough." Which of the following best describes the articulation?

Hip Board Review 2004: High-Yield MCQs (Set 2) - Figure 7

. Constrained to anteroposterior translation, unconstrained to medial-lateral translation, high contact stress on edge (ie, varus-valgus) loading
. Constrained to anteroposterior translation, unconstrained to medial-lateral translation, low contact stress on edge (ie, varus-valgus) loading
. Unconstrained to anteroposterior translation, constrained to medial-lateral translation, high contact stress on edge (ie, varus-valgus) loading
. Unconstrained to anteroposterior translation, constrained to medial-lateral translation, low contact stress on edge (ie, varus-valgus) loading
. Constraint is dependent on the status of the posterior cruciate ligament

Correct Answer & Explanation

. Constrained to anteroposterior translation, unconstrained to medial-lateral translation, high contact stress on edge (ie, varus-valgus) loading

Explanation

The theoretic total knee components will resist anteroposterior motion by making the femoral component "climb the walls" of the tibial component. As drawn, there is no constraint to medial-lateral translation. The cylinder is not rounded on the edges, so varus-valgus motion will impart load from the cylinder to the trough over a small area, thus having a high contact stress.

Question 2217

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old woman has a preoperative anterior interscalene block prior to undergoing a total shoulder arthroplasty. After seating her in the beach chair position, she becomes acutely hypotensive. What is the most likely cause for the hypotension?

. Tension pneumothorax
. Inadvertent epidural injection
. Inadvertent intravascular injection
. Laryngeal nerve block
. Bezold-Jarisch reflex

Correct Answer & Explanation

. Bezold-Jarisch reflex

Explanation

The beach chair position may cause sudden hypotension and bradycardia as a result of the Bezold-Jarisch reflex. This reflex occurs when venous pooling and increased sympathetic tone induce a low-volume, hypercontractile ventricle, resulting in activation of the parasympathetic nervous system and sympathetic withdrawal. The reported incidence of this phenomenon associated with the sitting position is between 13% to 24%. Left untreated, the result may be cardiac arrest. Pneumothorax or central nervous system toxicity after interscalene block is rare and has an incidence of less than 0.2%. Laryngeal nerve block associated with interscalene nerve block can occur but usually results in hoarseness secondary to ipsilateral vocal cord palsy. Long T, Wass C, Burkle C: Perioperative interscalene blockade: An overview of its history and current clinical use. J Clin Anesthesia 2002;14:546-556.

Question 2218

Topic: 3. Adult Reconstruction (Hip & Knee)

A 64-year-old man undergoes a primary total knee arthroplasty. Three months after surgery he reports persistent pain, weakness, and difficulty ambulating. Postoperative radiographs are shown in Figures 6a through 6c. What is the best course of action at this time?

. Hinged knee brace
. Patellar component revision with a tantalum implant and lateralization of the patella
. Revision knee arthroplasty with greater internal rotation of the tibial component
. Revision total knee arthroplasty with a lateral release and external rotation of the femoral component
. Revision total knee arthroplasty with a lateral release and internal rotation of the femoral component

Correct Answer & Explanation

. Revision total knee arthroplasty with a lateral release and external rotation of the femoral component

Explanation

The Merchant view reveals subluxation of the patellar component. The etiology of maltracking of the patella includes internal rotation of the femoral component, internal rotation of the tibial component, excessive patellar height, and lateralization of the patella component. The treatment of choice in this patient is revision total knee arthroplasty with external rotation of the femoral component. Preoperatively the patient also may require a lateral release, revision of the tibial component if it is internally rotated, and possibly a soft-tissue realignment. Component malalignment needs to be addressed first. Kelly MA: Extensor mechanism complications in total knee arthroplasty. Instr Course Lect 2004;53:193-199. Malkani AL, Karandikar N: Complications following total knee arthroplasty. Sem Arthroplasty 2003;14:203-214.

Question 2219

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old patient had the procedure shown in Figure 7 performed 5 years ago. When converting this patient to a total knee arthroplasty (TKA), what patellar problem is commonly encountered intraoperatively?

Hip & Knee Reconstruction 2007 Practice Questions: Set 1 (Solved) - Figure 16

. Fracture
. Patella baja
. Patella alta
. Osteonecrosis
. Maltracking

Correct Answer & Explanation

. Patella baja

Explanation

Patella baja is commonly encountered when converting a high tibial osteotomy (HTO) to a TKA. Patella baja most likely occurs because of scarring. Meding and associates' study did not show an increased rate of lateral release when converting a knee that had undergone a previous HTO. Yoshino N, Shinro T: Total knee arthroplasty after failed high tibial osteotomy, in Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, JB Lippincott, 2003, vol 2, pp 1265-1271.

Question 2220

Topic: 3. Adult Reconstruction (Hip & Knee)

Polyethylene wear of the bearing surface has been recognized as a mode of failure in total knee arthroplasty; therefore, many patients are offered polyethylene exchange. In terms of success rates, this surgical procedure has been reported to have a

. rate of less than 50%, primarily the result of infection.
. rate of greater than 50%.
. lower rate in patients in which metallosis was identified.
. similar rate with or without preoperative osteolysis.
. similar rate regardless of the degree of wear.

Correct Answer & Explanation

. similar rate with or without preoperative osteolysis.

Explanation

Engh and associates reported on the results of 63 knees (56 patients) following polyethylene exchange. The mean interval between exchange and the index total knee arthroplasty was 59 months. The mean follow-up after exchange was 7.4 years. Seven of 48 knees with adequate follow-up failed. Greater failure occurred if there was more severe wear before the exchange. Greater undersurface wear also resulted in a higher failure rate. Perioperative osteolysis or intraoperative observation of metallosis did not have an impact on the failure of polyethylene exchange. The risk of infection is no different from other total knee arthroplasty revisions. Wasielewski RC, Parks N, Williams I, et al: Tibial insert undersurface as a contributing source of polyethylene wear debris. Clin Orthop 1997;345:53-59.

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