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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 222 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 4421

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision THA for aseptic loosening of the acetabular component, it is discovered that the uncemented acetabular shell is well-fixed and difficult to remove without significant bone loss. The polyethylene liner is severely worn, and osteolysis is present around the shell-bone interface but not progressing beneath the shell. The femoral component is well-fixed and in good position. What is the most appropriate management of the acetabular component?

. Aggressively remove the well-fixed shell, reconstruct the defect, and implant a new uncemented shell.
. Leave the well-fixed shell in place, exchange the worn polyethylene liner, and bone graft the osteolytic lesions.
. Leave the well-fixed shell in place, cement a new polyethylene liner into the existing shell, and bone graft.
. Convert to a dual mobility construct by cementing a dual mobility component into the existing shell.
. Remove the entire THA and perform a Girdlestone resection arthroplasty.

Correct Answer & Explanation

. Aggressively remove the well-fixed shell, reconstruct the defect, and implant a new uncemented shell.

Explanation

This scenario describes aseptic loosening of the polyethylene liner within a well-fixed uncemented shell, with associated osteolysis. While simply exchanging the liner (option B) or cementing a new liner (option C) into anexistingshell is an option for isolated polyethylene wear without significant osteolysis or shell malposition, the presence of progressive osteolysis around the shell-bone interface implies that the current shell-bone interface is compromised, even if the shell initially feels well-fixed. Leaving the existing shell will perpetuate the problem and make future revisions more challenging. Therefore, the most appropriate management is to remove the existing shell, address the osteolysis (debridement, grafting), and implant a new, stable uncemented acetabular shell to ensure long-term stability and prevent further bone loss. This allows for restoration of the correct hip center and better control of acetabular mechanics. Converting to a dual mobility component without removing the problematic shell is not ideal given the osteolysis. Girdlestone is a salvage procedure.

Question 4422

Topic: 3. Adult Reconstruction (Hip & Knee)

A 50-year-old male presents with persistent thigh pain 5 years after an uncemented THA. Radiographs show no signs of component loosening, stable osteointegration, but significant proximal femoral stress shielding and distal cortical hypertrophy around the stem tip. Which of the following is the most likely diagnosis?

. Aseptic loosening of the femoral component.
. Periprosthetic joint infection.
. Stress shielding causing bone remodeling and thigh pain.
. Heterotopic ossification around the femoral stem.
. Femoral component malposition.

Correct Answer & Explanation

. Stress shielding causing bone remodeling and thigh pain.

Explanation

The patient's symptoms (thigh pain) combined with radiographic findings of proximal stress shielding and distal cortical hypertrophy in the absence of loosening or infection are classic for 'thigh pain' associated with uncemented, extensively porous-coated femoral stems. This phenomenon is attributed to the mismatch in stiffness between the stiff implant and the bone, leading to altered load transfer. The proximal bone is 'shielded' from stress, leading to resorption (stress shielding), while the distal femur experiences increased load, leading to cortical hypertrophy. This altered biomechanics can cause persistent pain. Aseptic loosening would show radiographic signs such as lucencies. PJI would typically have inflammatory markers and systemic symptoms. HO would be visible as bone formation around the implant. Malposition could cause pain but not typically this specific radiographic pattern of remodeling in the absence of loosening. Therefore, stress shielding and subsequent bone remodeling are the most likely cause.

Question 4423

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with a painful THA 10 years after implantation. Radiographs demonstrate focal osteolytic lesions around the acetabular component and within the acetabular bone, but the femoral component appears well-fixed without evidence of loosening or osteolysis. Inflammatory markers (ESR, CRP) are within normal limits, and joint aspiration culture is negative. What is the most appropriate management strategy for the acetabular side?

. Observe with serial radiographs and repeat inflammatory markers.
. Revision THA with exchange of both acetabular and femoral components.
. Acetabular revision with exchange of the polyethylene liner, debridement of osteolytic lesions, and bone grafting.
. Surgical debridement and antibiotic cement spacer placement.
. Long-term antibiotic suppression therapy.

Correct Answer & Explanation

. Acetabular revision with exchange of the polyethylene liner, debridement of osteolytic lesions, and bone grafting.

Explanation

This patient presents with aseptic osteolysis around the acetabular component, a common long-term complication of THA, often due to polyethylene wear debris. Given the isolated acetabular osteolysis with a well-fixed femoral component and negative infection workup, the most appropriate management is an isolated acetabular revision. This involves exchanging the worn polyethylene liner, debriding the osteolytic lesions, and bone grafting these lesions to prevent further bone loss and restore structural integrity. If the metal shell is well-fixed and in good position, it can be retained (a liner exchange procedure). However, often, if osteolysis is significant, the shell itself might be contributing or could become loose, necessitating a full shell revision. The option 'Acetabular revision with exchange of the polyethylene liner, debridement of osteolytic lesions, and bone grafting' (option C) broadly covers the necessary steps. Observing with serial radiographs is appropriate for small, non-progressive lesions but not for symptomatic, progressive osteolysis. Exchanging both components is unnecessary if the femoral component is well-fixed. Debridement with a spacer or antibiotics is for infection. Therefore, addressing the wear and bone loss specifically at the acetabulum is key.

Question 4424

Topic: Total Hip Arthroplasty (THA)

A 70-year-old male presents with a persistent Trendelenburg gait and pain over the greater trochanter 1 year after THA. MRI demonstrates discontinuity of the abductor tendons (gluteus medius and minimus) from the greater trochanter. What is the most appropriate surgical intervention?

. Physical therapy focusing on abductor strengthening.
. Corticosteroid injection into the trochanteric bursa.
. Revision THA with a larger femoral head to improve hip stability.
. Surgical repair of the abductor tendon to the greater trochanter.
. Excision of the greater trochanter.

Correct Answer & Explanation

. Surgical repair of the abductor tendon to the greater trochanter.

Explanation

Persistent Trendelenburg gait and pain over the greater trochanter, particularly with MRI evidence of abductor tendon discontinuity, strongly indicate abductor deficiency. This can be due to avulsion, non-healing of a trochanteric osteotomy, or direct injury during surgery (e.g., in a lateral approach). While physical therapy and injections might offer temporary symptomatic relief for bursitis, they do not address the underlying anatomical defect of tendon discontinuity. Revision THA with a larger femoral head primarily addresses instability, not abductor function. Excision of the greater trochanter is a drastic measure not indicated here. The most appropriate and definitive surgical intervention for abductor tendon discontinuity is direct surgical repair of the avulsed tendons to the greater trochanter. This aims to restore the continuity and function of the abductor mechanism, improving gait and reducing pain. Various techniques exist, including direct repair, advancement, or augmentation with allograft/autograft depending on the tissue quality.

Question 4425

Topic: Total Hip Arthroplasty (THA)
A 55-year-old female undergoes revision THA for recurrent dislocation. Intraoperatively, she is found to have a significant acetabular bone defect (Paprosky Type IIIB) with pelvic discontinuity. The surgeon plans to use a custom triflange acetabular component. What is the primary indication for using such a component in this scenario?
. To achieve biological ingrowth for long-term fixation.
. To bypass acetabular bone defects and provide stable fixation to intact pelvic bone.
. To allow for future liner exchange without full component revision.
. To reduce the risk of metal ion release from the acetabular shell.
. To provide increased jump distance and reduce dislocation risk.

Correct Answer & Explanation

. To bypass acetabular bone defects and provide stable fixation to intact pelvic bone.

Explanation

Custom triflange acetabular components are highly specialized implants used in complex revision THA cases, particularly for massive acetabular bone loss (Paprosky Type IIIB, sometimes Type III with pelvic discontinuity) where standard cages or conventional uncemented shells cannot provide stable fixation. The primary indication for these components is their ability to achieve stable, peripheral fixation to intact pelvic bone (e.g., ischium, ilium, pubis) bypassing the central acetabular defect and discontinuity. They are custom-designed from preoperative CT scans to perfectly match the patient's unique pelvic anatomy, providing a durable solution in otherwise unreconstructible acetabular defects. While they aim for biological ingrowth, their primary strength is mechanical stability in areas of severe bone loss, distributing load to healthy bone. The other options describe general benefits of THA components or are not the main indication for a triflange design.

Question 4426

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a history of hypertension and diabetes undergoes elective primary THA. Approximately 18 hours postoperatively, he suddenly develops acute hypotension (BP 80/40 mmHg), tachycardia (HR 120 bpm), hypoxia (SpO2 88% on room air), and altered mental status. There is no evidence of significant blood loss from the wound. What is the most likely diagnosis?

. Pulmonary embolism (PE).
. Periprosthetic joint infection (PJI).
. Fat embolism syndrome (FES).
. Acute myocardial infarction (AMI).
. Anaphylactic reaction to antibiotics.

Correct Answer & Explanation

. Fat embolism syndrome (FES).

Explanation

The patient's acute presentation with hypotension, tachycardia, hypoxia, and altered mental status in the immediate postoperative period after THA, without significant surgical site bleeding, is highly suggestive of Fat Embolism Syndrome (FES). FES typically occurs within 24-72 hours post-trauma or orthopedic surgery (especially long bone fractures or joint replacement) involving reaming or cementing. It involves the release of fat globules into the bloodstream, leading to pulmonary, cerebral, and systemic inflammatory responses. Pulmonary embolism often presents with acute dyspnea, pleuritic chest pain, and hypoxia, but the combination with hypotension and acute encephalopathy is more characteristic of FES. PJI would usually present later with fever and local signs. AMI would be more chest pain-centric, and anaphylaxis would usually present much sooner after drug administration. The constellation of respiratory, neurological, and circulatory symptoms points strongly to FES.

Question 4427

Topic: Total Hip Arthroplasty (THA)

During a primary THA, a significant leg length discrepancy (LLD) of 3 cm is noted intraoperatively with the ipsilateral limb being shorter. The surgeon has already reduced the hip and achieved stable component fixation. What is the most appropriate next step to address this LLD while minimizing complications?

. Accept the current LLD and counsel the patient on a shoe lift postoperatively.
. Perform a femoral shaft lengthening osteotomy to equalize limb length.
. Increase the neck-length of the femoral component by exchanging to a longer neck or a different stem version.
. Decrease the size of the acetabular component to lower the hip center.
. Perform a controlled release of the ipsilateral adductor and psoas muscles.

Correct Answer & Explanation

. Increase the neck-length of the femoral component by exchanging to a longer neck or a different stem version.

Explanation

Intraoperative leg length discrepancy >2-2.5 cm can lead to complications such as sciatic nerve palsy, lower back pain, and gait abnormalities. While accepting LLD with a shoe lift is an option for smaller discrepancies, 3 cm is significant. A femoral shaft lengthening osteotomy (option B) is a major procedure generally reserved for very large discrepancies or reconstructive needs outside of typical THA. Decreasing the acetabular component size (option D) would likely compromise stability and fixation. Controlled release of adductors and psoas (option E) is used to prevent impingement or to facilitate reduction in cases of severe contracture, but it doesn't directly lengthen the limb. The most practical and common intraoperative solution to address a short limb after initial stable reduction is to increase the effective neck length of the femoral component. This can be achieved by using a longer modular neck, a different femoral head length (e.g., +4, +8mm offset), or, if necessary, revising to a stem that allows for more lengthening, provided it doesn't compromise stability or risk neurovascular injury. This increases the offset and length without disturbing the established fixation of the stem or acetabulum.

Question 4428

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a history of Charcot arthropathy of the hip due to syringomyelia requires THA for pain and instability. What is the most significant challenge and perioperative consideration unique to THA in patients with Charcot arthropathy?

. Increased risk of heterotopic ossification.
. Difficulty in achieving stable implant fixation due to neurogenic osteolysis and bone fragility.
. Higher incidence of deep vein thrombosis.
. Challenges with postoperative pain management due to underlying neuropathy.
. Greater risk of periprosthetic joint infection.

Correct Answer & Explanation

. Difficulty in achieving stable implant fixation due to neurogenic osteolysis and bone fragility.

Explanation

Charcot arthropathy is a destructive joint disease caused by nerve damage, leading to loss of sensation and proprioception, which can result in repetitive microtrauma, bone resorption, and joint instability. For THA in the setting of Charcot arthropathy, the most significant challenge and perioperative consideration is the difficulty in achieving stable implant fixation due to neurogenic osteolysis and bone fragility (option B). The abnormal bone quality, often with significant bone loss and sclerosis, makes it challenging to achieve primary stability and long-term ingrowth for uncemented components. Patients with Charcot joints are also at a very high risk of accelerated bone resorption and prosthetic loosening postoperatively due to their ongoing neuropathy and lack of protective pain sensation. While other options (HO, DVT, infection, pain management) can be concerns, the unique challenge of bone quality and achieving durable fixation is paramount in Charcot joints, often requiring cemented fixation, custom implants, or extensive bone grafting.

Question 4429

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old male with a history of hypertension and diabetes presents with persistent pain, erythema, and purulent drainage from his left hip incision 6 months after a primary cementless total hip arthroplasty. A previous debridement, antibiotics, and implant retention (DAIR) procedure 3 months ago failed. Synovial fluid analysis prior to the DAIR showed a leukocyte count of 65,000 cells/µL with 92% neutrophils and culture grew Staphylococcus aureus (MRSA). Given the failed DAIR and chronic nature of the infection, what is the most appropriate next step in management?

. Another attempt at debridement, antibiotics, and implant retention (DAIR) with different antibiotic coverage.
. Chronic suppressive oral antibiotic therapy without surgical intervention.
. One-stage exchange arthroplasty with cementless components and antibiotic-loaded cement beads.
. Two-stage exchange arthroplasty with an antibiotic-loaded cement spacer followed by reimplantation.
. Resection arthroplasty (Girdlestone) without plans for reimplantation.

Correct Answer & Explanation

. Two-stage exchange arthroplasty with an antibiotic-loaded cement spacer followed by reimplantation.

Explanation

The patient has a confirmed chronic periprosthetic joint infection (PJI) with MRSA that failed a DAIR procedure. For chronic PJI, especially with resistant organisms or a failed DAIR, a two-stage exchange arthroplasty is the gold standard for eradication. This involves explantation of all components, thorough debridement, placement of an antibiotic-loaded cement spacer, and a period of systemic antibiotics, followed by reimplantation after infection markers normalize and cultures are negative. A one-stage exchange is an option in select cases (e.g., susceptible organism, good soft tissues, non-resistant infection), but for a failed DAIR with MRSA, two-stage is generally preferred due to higher success rates. Repeated DAIR for failed chronic PJI is unlikely to succeed. Chronic suppressive therapy may be considered for patients who are not surgical candidates but does not eradicate the infection. Resection arthroplasty is reserved for patients with severe comorbidities, extensive bone loss, or failed two-stage revisions, as it results in significant functional impairment.

Question 4430

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with severe left hip pain and inability to bear weight after a fall. She underwent a cementless total hip arthroplasty 10 years prior. Radiographs reveal a periprosthetic fracture of the femur classified as Vancouver B3. The femoral stem appears loose and has subsided significantly within the femur. What is the most appropriate definitive surgical management?

. Open reduction and internal fixation (ORIF) with plates and screws around the existing stem.
. Revision of the femoral stem using an extended trochanteric osteotomy and a long, modular cementless stem.
. Revision of the femoral stem with a cemented stem after removal of existing components.
. Explantation of the femoral stem, debridement, and placement of an antibiotic-loaded cement spacer.
. Pelvic reconstruction plate fixation with bone grafting.

Correct Answer & Explanation

. Revision of the femoral stem using an extended trochanteric osteotomy and a long, modular cementless stem.

Explanation

A Vancouver B3 periprosthetic fracture indicates a loose femoral stem with significant bone loss in the proximal femur. In such cases, the existing stem must be removed, and a new, more stable fixation obtained. ORIF around the existing loose stem is inappropriate. Cemented stems are generally used for elderly, low-demand patients, or in specific bone defects, but a long, modular cementless stem is often preferred for B3 fractures to bypass the fracture and achieve distal fixation, especially in cases with significant bone loss. An extended trochanteric osteotomy provides excellent exposure for stem removal and facilitates placement of a revision stem. Explantation for a spacer is for infection, not fracture. Pelvic reconstruction plates are for acetabular fractures, not femoral. Therefore, revision of the femoral stem with an extended trochanteric osteotomy and a long, modular cementless stem is the most appropriate definitive surgical management.

Question 4431

Topic: 3. Adult Reconstruction (Hip & Knee)
A 58-year-old male with a history of hip developmental dysplasia presents with severe acetabular bone loss (Paprosky Type IIIB) requiring revision total hip arthroplasty. The patient has a healthy, active lifestyle and good bone quality in the remaining pelvis. What is the most appropriate reconstructive option for his acetabular defect?
. Placement of a standard cementless hemispherical cup with supplemental screws.
. Impaction bone grafting with a standard cementless hemispherical cup.
. Use of a custom triflange acetabular component.
. Reconstruction with an antiprotrusio cage and bone graft.
. A jumbo hemispherical cementless cup with medialization.

Correct Answer & Explanation

. Use of a custom triflange acetabular component.

Explanation

Paprosky Type IIIB acetabular defects are characterized by extensive peripheral rim loss and medial wall deficiency, often with dissociation between the anterior and posterior columns. While standard hemispherical cups (A, E) are insufficient due to lack of peripheral support, and impaction grafting (B) is useful for contained defects, for severe uncontained defects like Type IIIB, a custom triflange acetabular component (C) offers the best chance for stable fixation by conforming to the patient's unique bone defect and providing screw fixation into viable bone. Antiprotrusio cages (D) are generally used for more contained medial wall defects or when the columns are intact. Given the patient's activity level and good bone quality, a custom component offers a durable solution.

Question 4432

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old male presents with increasing groin pain and limp 8 years after a left hip resurfacing arthroplasty. Radiographs show significant osteolysis around the acetabular component and a cystic lesion in the femoral neck, concerning for loosening and potential metallosis. Blood metal ion levels (cobalt and chromium) are significantly elevated. What is the most appropriate surgical management?

. Revision of the femoral resurfacing component only, with exchange to a conventional THA femoral stem.
. Revision of the acetabular resurfacing component only, with exchange to a conventional THA acetabular cup.
. Removal of both resurfacing components and conversion to a conventional total hip arthroplasty.
. Debridement and irrigation, followed by observation and metal ion level monitoring.
. Conservative management with pain medication and activity modification due to patient age.

Correct Answer & Explanation

. Removal of both resurfacing components and conversion to a conventional total hip arthroplasty.

Explanation

The patient's symptoms, radiographic findings of osteolysis and cystic lesions, and elevated metal ion levels are highly suggestive of adverse local tissue reaction (ALTR) or metallosis due to wear of the metal-on-metal resurfacing components. Both components likely contribute to the metal ion burden and are subject to failure. For symptomatic failure of hip resurfacing due to ALTR/metallosis, conversion to a conventional total hip arthroplasty (THA) is the gold standard. This involves removing both the femoral and acetabular resurfacing components and replacing them with standard THA components (typically ceramic-on-polyethylene or ceramic-on-ceramic) to eliminate the metal-on-metal bearing. Revising only one component (A or B) would not fully address the problem. Debridement and irrigation (D) without component removal is ineffective for ALTR. Conservative management (E) is not appropriate for symptomatic ALTR with significant osteolysis.

Question 4433

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female with a history of multiple previous abdominal surgeries presents for a revision total hip arthroplasty due to aseptic loosening of her cementless acetabular component. Intraoperatively, after removal of the old cup, a large contained cavitary defect (Paprosky Type 2B) is noted in the posterior superior acetabulum. The remaining acetabular bone appears healthy. What is the best strategy for managing this bone defect to ensure stable fixation of the new acetabular component?

. Omit bone grafting and rely solely on the new cementless cup's press-fit and screw fixation.
. Fill the defect with autogenous bone graft (e.g., reamings) and then implant a standard cementless cup.
. Use an uncemented jumbo cup that bypasses the defect.
. Utilize a cemented cup with a cage spanning the defect.
. Perform a complete acetabular reconstruction with an allograft-prosthesis composite.

Correct Answer & Explanation

. Fill the defect with autogenous bone graft (e.g., reamings) and then implant a standard cementless cup.

Explanation

For contained cavitary defects (Paprosky Type 2B), the strategy is to restore the geometry and provide support for the new acetabular component. Filling the defect with autogenous bone graft (e.g., reamings from reaming the healthy host bone) (B) is an excellent option as it provides biological fill and allows for ingrowth around the new cup. The new cementless cup can then be placed with good press-fit and supplemental screw fixation. Simply omitting bone grafting (A) might leave an unsupported area. Jumbo cups (C) are for uncontained defects. Cemented cups with cages (D) are generally reserved for more complex, uncontained defects or pelvic discontinuity. Allograft-prosthesis composites (E) are for massive defects. Therefore, filling the defect with autogenous bone graft and implanting a standard cementless cup is the most appropriate and common management for a contained cavitary defect.

Question 4434

Topic: 3. Adult Reconstruction (Hip & Knee)
A 48-year-old male presents with severe proximal femoral bone loss (Paprosky Type IV) due to chronic aseptic loosening of his previous revision femoral stem. The entire proximal femur is a sclerotic tube with massive cavitary defects and cortical thinning. The patient is otherwise healthy and active. What is the most appropriate reconstructive option for the femur?
. Long cemented revision stem with allograft chips.
. Modular cementless revision stem with distal fixation beyond the defect.
. Use of a custom femoral component designed to bypass the defect.
. Allograft-prosthesis composite (APC) using a proximal femoral allograft.
. A standard primary cementless femoral stem.

Correct Answer & Explanation

. Use of a custom femoral component designed to bypass the defect.

Explanation

Paprosky Type IV femoral defects involve extensive bone loss, often with a 'stovepipe' or sclerotic proximal femur, making traditional distal fixation challenging. In such cases, a custom femoral component (C) is often the best solution. It is designed preoperatively based on CT scans to precisely fit the remaining host bone and bypass the defect, achieving optimal distal fixation and rotational stability. While modular cementless revision stems (B) are excellent for Paprosky Type II and III defects, they may not provide adequate fixation or fill for Type IV. Allograft-prosthesis composites (D) are also an option for massive proximal femoral defects but carry risks of allograft nonunion, fracture, and infection. Long cemented stems (A) are less favored in active patients with extensive defects, and a standard primary stem (E) is clearly inadequate. Given the patient's activity level and the extent of the bone loss, a custom component offers a durable and precise solution.

Question 4435

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old immunocompromised patient undergoing a two-stage revision for periprosthetic joint infection (PJI) has persistently elevated inflammatory markers and positive cultures for Candida albicans from both the explanted tissue and the spacer during the first stage. What is the most appropriate next step in managing this fungal PJI?

. Proceed to the second-stage reimplantation after 6 weeks of systemic antibacterial antibiotics.
. Remove the current antibiotic-loaded cement spacer and insert a new one loaded with antifungal agents.
. Continue current systemic antibacterial antibiotics and add systemic antifungal therapy for an extended period.
. Perform a resection arthroplasty (Girdlestone) and discontinue plans for reimplantation.
. Administer intra-articular antifungal injections into the hip joint through the existing spacer.

Correct Answer & Explanation

. Remove the current antibiotic-loaded cement spacer and insert a new one loaded with antifungal agents.

Explanation

Fungal PJI is a severe and challenging complication. Standard antibacterial antibiotics are ineffective against fungal infections. If Candida albicans is cultured, the initial management involves thorough debridement, removal of all foreign material (including the existing spacer if it doesn't contain antifungal agents), and placement of a new spacer specifically loaded with antifungal agents (e.g., amphotericin B) in addition to systemic antifungal therapy (B). Proceeding to reimplantation (A) without addressing the fungal infection will lead to failure. Continuing antibacterial antibiotics (C) alone is ineffective. Resection arthroplasty (D) is a salvage option but not the first line when eradication might be possible. Intra-articular injections (E) are not a primary treatment for established fungal PJI. Therefore, the most appropriate next step is to address the fungal infection with targeted antifungal loaded components and systemic therapy.

Question 4436

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male undergoes revision THA for painful metallosis and pseudotumor formation related to a previously implanted metal-on-metal articulation. During the revision, both the femoral head and acetabular liner are replaced with ceramic-on-highly cross-linked polyethylene components. What is the most critical step to prevent recurrence of metallosis in this patient?

. Aggressive debridement of all pseudotumor tissue and thorough lavage.
. Implantation of a larger femoral head to increase jump distance.
. Use of antibiotic-loaded cement during component fixation.
. Postoperative administration of metal chelating agents.
. Long-term follow-up with regular blood metal ion level monitoring.

Correct Answer & Explanation

. Aggressive debridement of all pseudotumor tissue and thorough lavage.

Explanation

For revision THA due to metallosis and pseudotumor, the primary goal is to remove the source of the metal debris and excise the reactive tissue. Aggressive debridement of all pseudotumor tissue (A) and thorough lavage is critical to remove the inflammatory burden and any residual metal debris that could perpetuate the inflammatory response. While changing bearing surfaces eliminates the source, residual metallosis and pseudotumor must be excised. A larger femoral head (B) is for instability, not metallosis. Antibiotic-loaded cement (C) is for infection. Metal chelating agents (D) are not standard treatment for local tissue reactions from joint replacements. Long-term monitoring (E) is important but does not prevent recurrence; it merely detects it. Therefore, aggressive debridement is the most critical surgical step.

Question 4437

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with persistent groin pain 2 years after an uncomplicated primary cementless THA. Radiographs show well-fixed components with no signs of loosening, osteolysis, or heterotopic ossification. Inflammatory markers are normal, and aspiration of the joint is negative for infection. On physical exam, she has pain with resisted hip flexion and internal rotation. Which of the following is the most likely cause of her persistent pain?

. Aseptic loosening of the acetabular component.
. Periprosthetic joint infection.
. Iliopsoas impingement due to an overhanging acetabular component.
. Trochanteric bursitis.
. Stress fracture of the pubic ramus.

Correct Answer & Explanation

. Iliopsoas impingement due to an overhanging acetabular component.

Explanation

Given the patient's symptoms of persistent groin pain, pain with resisted hip flexion, and well-fixed components with no signs of infection or other obvious pathology, iliopsoas impingement (C) is a highly likely diagnosis. This occurs when the iliopsoas tendon rubs against an overhanging or anteriorly prominent acetabular component, particularly if the cup is placed with excessive anteversion or a larger than necessary component. Aseptic loosening (A) and PJI (B) are ruled out by imaging and workup. Trochanteric bursitis (D) would present with lateral hip pain. A pubic ramus stress fracture (E) would typically be associated with different pain characteristics and likely seen on imaging or bone scan.

Question 4438

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male with a 20-year history of a right hip arthrodesis for post-traumatic arthritis presents with increasing contralateral hip pain and ipsilateral low back pain. He desires conversion of his hip arthrodesis to a total hip arthroplasty (THA). Which of the following is a recognized major challenge and potential complication specific to converting a hip arthrodesis to THA?

. Increased risk of deep vein thrombosis due to prolonged surgery.
. Higher rates of prosthetic joint infection due to previous surgery.
. Significant limb length discrepancy and potential for neurovascular injury with lengthening.
. Limited intraoperative exposure due to fibrous ankylosis.
. Higher risk of avascular necrosis of the femoral head.

Correct Answer & Explanation

. Significant limb length discrepancy and potential for neurovascular injury with lengthening.

Explanation

Converting a hip arthrodesis to THA is a complex procedure with several unique challenges. Significant limb length discrepancy (LLD) is common, as the fused hip often limits growth and positioning. Correcting LLD can involve substantial femoral lengthening, which carries a high risk of sciatic or femoral nerve palsy (neurovascular injury) due to stretch (C). While DVT risk (A) and PJI risk (B) are generally higher in revision surgery, the specific challenge of nerve injury due to limb lengthening is paramount in arthrodesis conversion. Limited exposure (D) can be challenging but is overcome with appropriate extensile approaches. Avascular necrosis of the femoral head (E) is not a direct complication of this procedure, as the femoral head is typically replaced.

Question 4439

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a history of cervical cancer treated with pelvic radiation 10 years prior requires a total hip arthroplasty for severe post-radiation osteonecrosis. What is the most significant anticipated complication specific to performing THA in a previously irradiated hip?

. Increased risk of intraoperative periprosthetic fracture due to weakened bone.
. Higher incidence of deep vein thrombosis.
. Greater difficulty with wound healing and increased risk of infection.
. More challenging pain management due to neuropathic pain.
. Reduced long-term implant survival due to poor bone integration.

Correct Answer & Explanation

. Greater difficulty with wound healing and increased risk of infection.

Explanation

Pelvic radiation causes damage to soft tissues (skin, subcutaneous tissue, muscle) and bone, leading to fibrosis, impaired vascularity, and reduced cellularity. This significantly compromises wound healing and increases the risk of infection (C). The weakened and sclerotic bone (A) can also lead to increased risk of intraoperative fracture and reduced long-term implant survival (E) due to poor osseointegration, but wound healing and infection are often the most immediate and challenging complications to manage. DVT risk (B) is general to surgery. Neuropathic pain (D) is a possible long-term effect of radiation but not the most significant surgical complication.

Question 4440

Topic: 3. Adult Reconstruction (Hip & Knee)

For a 40-year-old active male undergoing primary THA for avascular necrosis, which bearing surface combination is generally considered to offer the best long-term durability and lowest wear rates, assuming no contraindications (e.g., allergy, renal disease)?

. Metal-on-polyethylene (MoP) with a standard polyethylene liner.
. Ceramic-on-polyethylene (CoP) with a highly cross-linked polyethylene liner.
. Metal-on-metal (MoM) with a large diameter femoral head.
. Ceramic-on-ceramic (CoC) with a large diameter femoral head.
. Metal-on-polyethylene (MoP) with a conventional polyethylene liner and small femoral head.

Correct Answer & Explanation

. Ceramic-on-ceramic (CoC) with a large diameter femoral head.

Explanation

For young, active patients requiring long-term durability, ceramic-on-ceramic (CoC) bearings (D) have historically demonstrated the lowest wear rates and negligible osteolysis in studies, making them an excellent choice for longevity. Highly cross-linked polyethylene (HXLPE) has significantly improved the wear performance of CoP bearings (B), making them a very popular and durable option, but CoC generally shows even lower wear. Metal-on-metal (C) has fallen out of favor due to concerns regarding metallosis, adverse local tissue reactions, and pseudotumor formation. Standard polyethylene (A, E) has higher wear rates compared to HXLPE and ceramics.

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