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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 51 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 1001

Topic: 3. Adult Reconstruction (Hip & Knee)
A 57-year-old woman experiences pain 1 year after total knee arthroplasty (TKA). She reports sharp anterior pain and a painful catching sensation that is aggravated by rising from a chair or climbing stairs. Physical examination reveals a mild effusion and a range of motion of 2° to 130°, with patellar crepitus. The symptoms are reproduced by resisted knee extension. Radiographs show a well-aligned posterior-stabilized TKA without evidence of component loosening. What is the recommended treatment for this patient?
. Physical therapy
. Arthroscopic synovectomy
. Tibial insert revision
. Femoral component revision

Correct Answer & Explanation

. Arthroscopic synovectomy

Explanation

DISCUSSION: Patellar clunk syndrome is caused by the development of a fibrous nodule on the posterior aspect of the quadriceps tendon at its insertion into the patella. It causes a painful catching sensation when the extensor mechanism traverses over the trochlear notch as the knee extends from 45° of flexion to 30° from full extension. It characteristically occurs in posterior-stabilized total knee arthroplasties and appears to be related to femoral component design. The syndrome can usually be prevented by excising the residual synovial fold just proximal to the patella. Flexion gap instability can also cause a painful total knee arthroplasty but is less common in posterior-stabilized implants. Femoral component malrotation can cause pain attributable to a flexion gap imbalance or patellar tracking problems. Polyethylene wear would be unlikely after just 1 year. Patellar clunk syndrome can usually be addressed successfully with arthroscopic synovectomy. Recurrence is uncommon. Physical therapy may help to strengthen the quadriceps following synovectomy but would not resolve the clunk syndrome symptoms. Femoral or tibial insert revision is not indicated if patellar clunk syndrome is the only problem resulting in a painful total knee arthroplasty.

Question 1002

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

DISCUSSION: 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 patellar 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.

Question 1003

Topic: 3. Adult Reconstruction (Hip & Knee)
Figures 28a and 28b show the radiographs of a 79-year-old man who has constant knee pain. Prior to performing elective knee replacement surgery, management should include
. reduction of the serum alkaline phosphatase level by 50%.
. preoperative radiation therapy of 600 cGy to the surgical site.
. aspiration of the knee joint with cell count.
. insertion of a vena caval filter.
. administration of 25 mg of indomethacin three times a day.

Correct Answer & Explanation

. reduction of the serum alkaline phosphatase level by 50%.

Explanation

DISCUSSION: The radiographs show established Paget’s disease. Bony expansion is evident, with thickened trabeculae consistent with the disordered bone remodeling process. A reduction of the serum alkaline phosphatase level to 50% of the pretreatment level may reduce pain from Paget’s disease, and it is recommended prior to consideration of joint replacement. In elective cases, treatment of Paget’s disease should begin at least 6 weeks prior to surgery. The other modalities are not related to the treatment of Paget’s disease.

Question 1004

Topic: Total Knee Arthroplasty (TKA)

below shows the standing AP radiograph obtained from a year-old man who has a year history of daily left knee medial joint line pain with weight-bearing activities. He denies night pain or symptoms of instability. On examination, his range of motion is 0° to 140°. He has a mild, fully correctable varus deformity and a negative Lachman test result. Nonsurgical treatment has failed. Unicompartmental knee arthroplasty (UKA) is discussed with the patient. The most appropriate next radiographic evaluation should be

. MRI of the left knee to evaluate the lateral compartment.
. a CT arthrogram to evaluate the status of the medial and lateral meniscus. C. a stress radiograph to evaluate correction of the varus deformity.
. a sunrise view to determine the status of the patellofemoral joint.

Correct Answer & Explanation

. MRI of the left knee to evaluate the lateral compartment.

Explanation

DISCUSSION:A  patient  with  medial  compartment  arthritis  and  a  correctable  varus  deformity  with  no  clinical  or examination findings of knee instability most likely has an intact anterior cruciate ligament (ACL). The pattern of medial compartment osteoarthritis most commonly associated with an intact ACL is that of anteromedial osteoarthritis. An incompetent ACL is commonly associated with a fixed varus deformity and radiographic signs of posteromedial wear. An incompetent ACL is a relative contraindication to a mobile-bearing UKA. When evaluating patients for a mobile-bearing UKA, a stress radiograph aids the orthopaedic  surgeon  in  determining  the  correction  of  the  varus  deformity  and  assessing  the  lateral compartment. An inability to fully correct the deformity or narrowing of the lateral compartment with valgus stress should influence the surgeon against UKA. Joint registries across the world have shown decreased  survivorship  associated  with  TKA  and  UKA  in  men  compared  with  other  age  groups,  but survivorship  is  lower  for  UKA  than  for  TKA.  No  studies  to  date  have  shown  any  differences  in survivorship  between  fixed-bearing  and  mobile-bearing  UKAs.  The  complication  that  is  unique  to mobile-bearing  UKA  is  bearing  spinout,  which  occurs  in  less  than  1%  of  mobile-bearing  UKA procedures. In vivo and in vitro polyethylene wear in mobile-bearing UKA are low. Arthritis may progressfaster in patients with mobile-bearing UKAs than in those with fixed-bearing UKAs.

Question 1005

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures below depict the radiographs obtained from a 76-year-old woman who comes to the emergency department after experiencing a fall. She is an unassisted community ambulator with a history of right hip pain. What is the most appropriate surgical treatment for this fracture?

. Cemented unipolar hemiarthroplasty
. Cemented bipolar hemiarthroplasty
. Total hip replacement
. Open reduction and internal fixation

Correct Answer & Explanation

. Cemented unipolar hemiarthroplasty

Explanation

DISCUSSION:This patient has pre-existing right hip osteoarthritis. The most correct option for the treatment of this active patient is a right total hip arthroplasty. Hemiarthroplasty would not address the patient's pain from osteoarthritis, and open reduction and internal fixation would not fix the femoral head issue or the osteoarthritis.

Question 1006

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 18 shows the radiograph of a patient with a total hip arthroplasty dislocation. During revision, increasing the diameter of the femoral head while maintaining the ratio of head-to-neck diameter constant has the effect of

. increasing the force to dislocation of the femoral head.
. increasing the range of motion until impingement of the neck on the liner.
. decreasing the resisting moment to dislocation of the femoral head.
. decreasing the range of motion until dislocation of the femoral head.
. decreasing the range of motion until impingement of the neck on the liner.

Correct Answer & Explanation

. increasing the force to dislocation of the femoral head.

Explanation

DISCUSSION: Although there is strong clinical and laboratory evidence that suggests smaller head size is linked with lower rates of polyethylene wear, moving to the use of 22-mm heads from larger sizes would tend to increase the dislocation rate.  The key premise to this argument is that the absolute size of the femoral neck remains unchanged.  While neck diameters were appropriate for the early monoblock femoral components, the use of modular femoral stems allows the surgeon to place 22-mm heads onto the same neck and trunion as used by larger heads.  This has the effect of lessening the head-to-neck diameter ratio, which then accentuates the rate of impingement and dislocation.  Reducing the neck diameter in proportion to the head diameter would eliminate the range-of-motion penalty accompanying head size reduction.Scifert and associates used a three-dimensional finite element model to study various combinations of femoral head size and neck ratios.  They found that increasing the diameter of the femoral head while maintaining a constant head-to-neck diameter had the effect of significantly increasing the resisting moment necessary to induce a dislocation.  The higher the head-to-neck ratio, the greater the range of motion until impingement and the greater the range of motion to dislocation.REFERENCE: Scifert CF, Brown TD, Pedersen DR, Callaghan JJ: A finite element analysis of factors influencing total hip dislocation.  Clin Orthop 1998;355:152-162.

Question 1007

Topic: 3. Adult Reconstruction (Hip & Knee)

Five weeks after the patient completes a 6-week course of antibiotics, his ESR is 24 mm/h and CRP level is 10 mg/L, which is similar to the levels at 6 weeks. What is the most appropriate treatment at this time?

. Delay further surgical intervention until his ESR and CRP level normalize
. Delay further surgical intervention until his ESR normalizes
. Delay further surgical intervention until his CRP level normalizes
. Proceed with surgical intervention if the patient’s condition is medically optimized

Correct Answer & Explanation

. Delay further surgical intervention until his ESR and CRP level normalize

Explanation

DISCUSSIONThis patient has both serologic and synovial fluid findings that are concerning for indolent infection. He was taking antibiotics at the time of aspiration. The AAOS clinical practice guideline, The Diagnosis of Periprosthetic Joint Infections of the Hip and Knee, suggests that patients discontinue antibiotics for a minimum of 2 weeks and that a repeat aspiration should be performed in cases of contradictory findings. In this situation, the cell count is elevatedalong with an elevated ESR and CRP level. As a result, the appropriate treatment at this time is to reaspirate his hip.This patient has a periprosthetic joint infection with a draining sinus tract. He has had symptoms for several months and, as a result, irrigation and debridement are not indicated. A single-stage surgery may be performed in some centers for healthy patients with susceptible organisms. However, single-stage reconstructions are generally performed with cemented implants in patients without a draining sinus tract. A 2-stage procedure with an antibiotic spacer is the surgical treatment modality most likely to eradicate this infection.Serologic findings have significantly improved since the time of the prior surgical procedure. Surgical intervention does not need to be delayed until these values have completely normalized.

Question 1008

Topic: 3. Adult Reconstruction (Hip & Knee)

A year-old man has a draining sinus and recurrent infection of his right total knee arthroplasty. He has had two prior revision surgeries after the primary procedure and three other surgeries before his initial replacement, including a proximal tibial osteotomy and subsequent hardware removal. On clinical examination, he has a draining sinus in the mid portion of his surgical scar and a range of motion of 5° to 85°. AP and lateral radiographs of the right knee are shown in below. During surgery, the femoral component is found to be grossly loose, but the tibial component is well fixed. What is the most appropriate extensile approach that would provide adequate exposure and aid in tibial component extraction?

. Extended medial parapatellar approach
. Quadriceps snip
. Extended tibial tubercle osteotomy
. Medial epicondyle osteotomy

Correct Answer & Explanation

. Extended medial parapatellar approach

Explanation

DISCUSSION:Extended tibial tubercle osteotomy is an extensile approach to revision total knee arthroplasty that affords excellent exposure and can facilitate removal of tibial sleeves and cones. This patient has had multiple surgeries, including a proximal tibial osteotomy, as well as poor range of motion, patella baja, and a well- fixed  metaphyseal  sleeve  component.  Classically,  an  extended  tibial  tubercle  osteotomy  provides outstanding exposure for component removal in the setting of prior high tibial osteotomy and patella baja. For this patient, it is important to recognize the patella baja on the radiographs, as well as the tibial sleeve. In many of these cases the osteotomy provides access to the sleeve to help with extraction, because the stem will not pull through the sleeve or detach from the tray to allow visualization of the sleeve. The extended medial parapatellar approach is just a long medial approach that typically yields good exposurebut would not help with the patella baja or extraction of the tibial sleeve. The quadriceps snip would give good exposure to the knee but would not aid in tibial component removal. Lastly, the medial epicondyle osteotomy could help with exposure and tensioning of the medial complex of the knee but would not helpwith tibial component extraction.

Question 1009

Topic: 3. Adult Reconstruction (Hip & Knee)

A 51-year-old male truck driver has had progressive left hip pain for more than 2 years, and he reports that the pain has become severe in the past 9 months. He is now unable to work because of the pain. Examination reveals that range of motion of the hip is limited to 95 degrees of flexion, 0 degrees of internal rotation, and 20 degrees of external rotation. The plain radiograph, MRI scan, and intraoperative gross photographs are shown in Figures 9a through 9d. Management should consist of

. synovectomy.
. local excision with arthroplasty.
. radiation synovectomy.
. radiation therapy.
. radical resection.

Correct Answer & Explanation

. synovectomy.

Explanation

DISCUSSION: The diagnosis is synovial chondromatosis.  While the plain radiograph fails to show any calcifications, the MRI scan shows an intra-articular mass that involves the capsule.  Grossly multiple granular cartilage nodules are seen.  Management should consist of removing all loose bodies along with the synovial membrane.REFERENCE: Milgram JM: Synovial osteochondromatosis: A histopathological study of thirty cases.  J Bone Joint Surg Am 1977;59:792-801.

Question 1010

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 10 shows the radiograph of an active 75-year-old woman who reports severe leg pain after a fall. Management should consist of

. a total hip arthroplasty with a long-stem prosthesis.
. a resection arthroplasty with skeletal traction.
. hemiarthroplasty with a long-stem prosthesis.
. retention of the prosthesis and open reduction and internal fixation.
. closed treatment with skeletal traction.

Correct Answer & Explanation

. a total hip arthroplasty with a long-stem prosthesis.

Explanation

DISCUSSION: The patient has a comminuted fracture of the proximal femur and joint space narrowing of the acetabulum.  Therefore, the prosthesis should be converted to a total hip arthroplasty.  Because there is extensive comminution, the revision stem should bypass the area of bone loss by two bone diameters.  A hemiarthroplasty is not indicated because the patient has no acetabular cartilage.  Open reduction and internal fixation may not stabilize the prosthesis.  A resection arthroplasty or treatment in traction will not leave the patient with adequate function.REFERENCES: Garbuz DS, Masri BA, Duncan CP: Periprosthetic fractures of the femur: Principles of prevention and management, in Cannon WD Jr (ed): Instructional Course Lectures 47.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 237-242.Montijo H, Ebert FR, Lennox DA: Treatment of proximal femur fractures associated with total hip arthroplasty.  J Arthroplasty 1989;4:115-123.

Question 1011

Topic: Total Hip Arthroplasty (THA)

Varus intertrochanteric osteotomy for coxa valga commonly produces which of the following results?

. Decreased abductor lever arm
. Increased hip joint reaction force
. Increased center edge angle
. Abductor lag and lurch
. Lengthening of the leg

Correct Answer & Explanation

. Decreased abductor lever arm

Explanation

DISCUSSION: The greater trochanter is raised as a by-product of varus osteotomy, and a temporary abductor lag and lurch is common for 6 months following surgery.  In the absence of hip joint subluxation, varus intertrochanteric osteotomy has no effect on the center edge angle of Wiberg.  Varus osteotomy typically increases femoral offset, thereby improving the abductor lever arm and reducing the hip joint reaction force.  Even without taking a wedge, varus osteotomy always produces some degree of shortening.REFERENCE: Millis MB, Murphy SB, Poss R : Osteotomies about the hip for the prevention and treatment of osteoarthrosis.  Instr Course Lect 1996;45:209-226.

Question 1012

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 30a is the anteroposterior radiograph of a 20-year-old woman with mild right groin pain and intermittent “catching” in the hip region. What is the most appropriate next step? tear

. Arthroscopic evaluation and treatment of the hypertrophic labrum and a possible labral
. A hip injection to confirm an intra-articular source of the pain
. Nonsurgical treatment and subsequent total hip arthroplasty (THA) when the patient is
. sufficiently symptomatic
. Periacetabular osteotomy

Correct Answer & Explanation

. Arthroscopic evaluation and treatment of the hypertrophic labrum and a possible labral

Explanation

DISCUSSIONBecause this patient is young, substantial bilateral acetabular dysplasia is present, and the joint space is well preserved, periacetabular osteotomy is the treatment of choice (Figure 30b). Arthroscopic evaluation and treatment is insufficient to address the mechanical deformity. Although a hip injection can be diagnostically helpful, it would not alter the treatment plan in this scenario. The patient’s young age would make observation and subsequent THA less desirable. Femoral osteotomies also were performed to address rotational deformity.

Question 1013

Topic: 3. Adult Reconstruction (Hip & Knee)

A 77-year-old man with a history of mild renal insufficiency and atrial fibrillation on warfarin therapy is scheduled to undergo a left total hip arthroplasty. He previously underwent a right total hip arthroplasty with development of significant heterotopic bone that resulted in limitation of motion. What is the most appropriate form of prophylactic treatment to minimize the formation of heterotopic bone on his left hip?

. Postoperative indomethacin for 3 weeks
. Postoperative indomethacin for 6 weeks
. No treatment indicated; can treat later if heterotopic bone forms
. 800 centigrey of radiation given to the periprosthetic soft tissues preoperatively on the morning of surgery
. 400 centigrey of radiation given to the periprosthetic soft tissues day 2 postoperatively

Correct Answer & Explanation

. Postoperative indomethacin for 3 weeks

Explanation

DISCUSSION: This question centers on the prophylactic treatment to reduce the risk of heterotopic bone formation. Prophylaxis is indicated because he has already demonstrated bone formation with his prior hip arthroplasty, which places him at increased risk for developing heterotopic bone on the contralateral side. He is on warfarin and has renal insufficiency, which makes the use of NSAIDs contraindicated. The recommended dose is 600 to 800 centigrey of radiation given within 24 hours of surgery preoperatively or 72 hours postoperatively.REFERENCES: Kolbl O, Knelles D, Barthel T, et al: Preoperative irradiation versus the use of nonsteroidal anti-inflammatory drugs for prevention of heterotopic ossification following total hip replacement: The results of a randomized trial. Int J Radiat Oncol Biol Phys 1998;42:397-401.Pakos EE, Ioannidis JP: Radiotherapy vs nonsteroidal anti-inflammatory drugs for the prevention of heterotopic ossification after major hip surgery: A meta-analysis of randomized trials. Int J Radiat Oncol Biol Phys 2004;60:888-895.Seegenschmiedt MH, Makoski HB, Micke O, et al: Radiation prophylaxis for heterotopic ossification about the hip joint: A multicenter study. Int J Radiat Oncol Biol Phys 2001 ;51:756-765.Figure 23 a Figure 23b

Question 1014

Topic: 3. Adult Reconstruction (Hip & Knee)

A 56-year-old woman underwent a total knee arthroplasty 2 years ago and now has pain and swelling. Radiographs of her knee are unremarkable. Her C-reactive protein (CRP) level is 3.0 (reference range [rr], 0.08–3.1 mg/L), and her erythrocyte sedimentation rate (ESR) is 18 mm/h (rr, 0-20 mm/h). Aspiration of the knee reveals a white blood cell (WBC) count of 1200/mm3 with a differential of 30% neutrophils and 70% monocytes. Cultures will not be available for several days, and the patient has not been taking antibiotics. Based on these findings, the most appropriate next step is

. arthrotomy, irrigation, and tibial polyethylene exchange.
. parenteral antibiotics.
. nonsurgical treatment without antibiotics.
. removal of the implant and a 2-stage procedure.

Correct Answer & Explanation

. arthrotomy, irrigation, and tibial polyethylene exchange.

Explanation

DISCUSSIONESR and CRP level are recommended as starting points in the workup for the diagnosis or exclusion of periprosthetic joint infection (PJI). When both the ESR and CRP findings are within defined limits, PJI is unlikely. When both test findings are positive, PJI must be considered and further investigation is warranted. Clinicians need to be aware of other inflammatory conditions such as rheumatoid arthritis that can lead to elevation of inflammatory markers.A high likelihood of infection is noted when the knee aspirate contains more than 2500 WBCs per high-powered field (HPF) with a differential count exceeding 60% neutrophils. Using these criteria, Mason demonstrated a sensitivity of 98% and a specificity of 95% for infection diagnosis.For this patient, the inflammatory markers are within normal limits. The aspiration result is below 2500 WBC/HPF with a low percentage of neutrophils. The likelihood of infection is remote, and further nonsurgical treatment should not include antibiotics. There is no indication for surgery based upon the information presented.

Question 1015

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary concern for arthrodesis of a failed infected total knee arthroplasty using internal fixation?

. Recurrent infection
. Lack of stability
. Lack of soft-tissue coverage
. Stress shielding
. Stress risers

Correct Answer & Explanation

. Recurrent infection

Explanation

DISCUSSION: Arthrodesis of the failed infected total knee arthroplasty may be accomplished by external fixation, intramedullary rod fixation, and dual plates and screws.  External fixation runs the risk of pin tract infection, although after its removal, there are no metal surfaces left in place.  Intramedullary rods have been used successfully in the treatment of infected total knees, although they also leave metal within the region of the infection.  The dual plate technique of knee fusion is useful in patients with rheumatoid arthritis who require fusion in the absence of infection because it provides good initial stability and avoids the use of external pins.  However, in the face of infection, the large surface area of the screws and plates may serve as a site for bacteria to hide within a glycocalyx and make eradication of the infection almost impossible.REFERENCE: Windsor RE: Knee arthrodesis, in Insall JN, Windsor R, Kelly M, et al (eds): Surgery of the Knee.  New York, NY, Churchill Livingstone, 1993, pp 1103-1116.

Question 1016

Topic: 3. Adult Reconstruction (Hip & Knee)

After trial placement of components in a primary total knee arthroplasty, the knee is unable to come to full extension, but the flexion gap is appropriately balanced. After adequate soft-tissue releases have been performed, what is the next most appropriate action to balance the reconstruction?

. Use a larger femoral component
. Use a thinner polyethylene insert
. Add posterior femoral augments
. Resect more proximal tibia
. Resect additional distal femur

Correct Answer & Explanation

. Use a larger femoral component

Explanation

DISCUSSION: The reconstruction requires additional resection of the distal femur to allow increased extension while maintaining the current flexion gap tension.  Resecting more proximal tibia or decreasing the tibial polyethylene thickness will decrease flexion tension as well as extension tension.  Adding posterior femoral augments and using a larger femoral component will increase flexion tension.REFERENCES: Ayers DC, Dennis DA, Johanson NA, et al: Common complications of total knee arthroplasty.  J Bone Joint Surg Am 1997;79:278-311.Pelicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 281-286.

Question 1017

Topic: 3. Adult Reconstruction (Hip & Knee)

Among patients with lumbar degenerative disk disease and low back pain, what factor is most predictive of clinical outcomes after surgical management? Review Topic

. Duration of symptoms
. Workers' compensation
. Use of disk arthroplasty
. Severity of disk degeneration
. Number of spinal segments treated

Correct Answer & Explanation

. Duration of symptoms

Explanation

The treatment of low back pain ranges from nonsurgical management to surgical management. Whereas many other treatment modalities have been investigated, lumbar arthrodesis remains the primary surgical treatment of lumbar diskogenic pain. Outcomes of surgical management vary but are consistently impacted negatively by workers' compensation status. Neither the radiographic severity of disease, number of spinal segments, nor duration of disease has been correlated with clinical outcomes. While total disk arthroplasty was hoped to be an improvement over fusion, the evidence available to date has shown no significant differences over arthrodesis.

Question 1018

Topic: 3. Adult Reconstruction (Hip & Knee)

A large circumferential proximal femoral allograft is to be used in the reconstruction of a failed femoral component in a total hip arthroplasty. To enhance fixation of the graft to the implant, which of the following strategies should be used?

. Modern cement technique
. Porous-coated stem
. Nonporous press-fit stem
. Hydroxyapatite-coated stem
. Cerclage wire fixation

Correct Answer & Explanation

. Modern cement technique

Explanation

DISCUSSION: The optimum treatment is cementing the implant to the allograft.  Press-fit stability is unreliable. Wires and screws may be used for an incomplete proximal femoral allograft but cannot be used to anchor a complete proximal femoral allograft.REFERENCES: Allan DG, Lavoie GJ, Rudan JF, et al: The use of allograft bone in revision total hip arthroplasty, in Friedlaender GE, Goldberg VM (eds): Bone and Cartilage Allografts: Biology and Clinical Applications. Park Ridge, IL, American Academy of Orthopaedic Surgeons, 1991, pp 263-264.Gross AE, Lavoie MV, McDermott P, Marks P: The use of allograft bone in revision of total hip arthroplasty. Clin Orthop 1985;197:115-122.Head WC, Berklacich FM, Malinin TI, Emerson RH Jr: Proximal femoral allografts in revision total hip arthroplasty. Clin Orthop 1987;225:22-36.

Question 1019

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures 1 and 2 demonstrate the radiographs obtained from a 35-year-old woman with end-stage debilitating osteoarthritis of the right hip. She is contemplating total hip arthroplasty (THA). She has a history of right hip dysplasia and underwent hip osteotomy as an adolescent. Over the years, nonsurgical treatment, including weight loss, activity modifications, and intra-articular injections, has failed. Her infection work-up reveals laboratory findings within defined limits. Which bearing surface is contraindicated for this patient?

. Ceramic-on-ceramic
. Ceramic-on-highly cross-linked polyethylene (HXPE)
. Metal-on-HXPE
. Metal-on-metal

Correct Answer & Explanation

. Ceramic-on-ceramic

Explanation

DISCUSSION:THA has proven durable and reliable for pain relief and improving function for patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A metal-on-metal articulation is associated with excellent wear rates in vitro. With its capacity to offer a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis with potential transfer of metal ions across the placental barrier make metal-on-metal bearings less desirable and relatively contraindicated for younger women of childbearing age. The workup of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including sedimentation rate, CRP, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging including MARS MRI should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so, when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cell counts. 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.

Question 1020

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following treatments of polyethylene results in the highest amount of oxidative degradation?

. Ethylene oxide sterilization
. Gamma irradiation in air
. Gamma irradiation in an inert environment
. Gamma irradiation followed by cross-linking
. Gas plasma sterilization

Correct Answer & Explanation

. Ethylene oxide sterilization

Explanation

DISCUSSION: Oxidative degradation of polyethylene occurs as a function of time in an air environment.  In an environment such as argon, nitrogen, or a vacuum, the process is reduced.  Ethylene oxide is an alternative for sterilization in which the cross-link degradation is minimized because of the absence of oxidative interactions. Gamma sterilization or use of ethylene oxide gas is the industry standard; however, oxygen concentrations are now reduced to a minimal level to retard the oxidation phenomenon.REFERENCES: Sanford WM, Saum KA: Accelerated oxidative aging testing of UHMWPE. Trans Orthop Res Soc 1995;20:119.Sun DC, Schmidig G. Stark C, et al: On the origins of a subsurface oxidation maximum and its relationship to the performance of UHMWPE implants. Trans Soc Biomater 1995;18:362.Callaghan JJ, Dennis DA, Paprosky WA, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 35-41.McKellup HA: Bearing surfaces in total hip replacement: State of the art and future developments. Instr Course Lect 2001;50:165-179.

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