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 4401
Topic: 3. Adult Reconstruction (Hip & Knee)
What is the primary vascular supply to the lunate that is at risk during a lunate dislocation?
Correct Answer & Explanation
. Branches from both radial and ulnar arteries forming dorsal and volar arterial networks
Explanation
The lunate receives its blood supply from branches of both the radial and ulnar arteries, which form dorsal and volar arterial networks that penetrate the bone. This dual supply makes it susceptible to avascular necrosis when these networks are disrupted, which is common in dislocations where the lunate's ligamentous attachments (and thus vascular pedicles) are torn. Options A and B are partially correct but do not encompass the full, dual supply. Interosseous arteries contribute distally but are not the primary direct supply to the lunate itself in this context.
Question 4402
Topic: 3. Adult Reconstruction (Hip & Knee)
What is the earliest reliable indicator of potential avascular necrosis of the lunate on plain radiographs after a lunate dislocation?
Correct Answer & Explanation
. Increased density (sclerosis) of the lunate
Explanation
The earliest reliable radiographic indicator of avascular necrosis (AVN) of the lunate (Kienböck's disease) is increased density or sclerosis of the lunate. This is due to ischemic bone death, followed by new bone formation and trabecular thickening, which makes the bone appear denser on radiographs. Subchondral collapse is a later stage. Decreased signal intensity on T1-weighted MRI is a more sensitive and earlier indicator than X-ray, but the question specifies plain radiographs. Increased radiolucency would be rare in AVN and increased joint space is not a direct sign of AVN itself.
Question 4403
Topic: 3. Adult Reconstruction (Hip & Knee)
An adult male with a known history of Spondyloepiphyseal Dysplasia Tarda presents to the orthopedic clinic with progressively worsening, debilitating groin pain. Given the natural history of this disease, which surgical procedure is he most likely to require in his 30s or 40s?
Correct Answer & Explanation
. Total hip arthroplasty
Explanation
Patients with SED Tarda characteristically develop severe, premature secondary osteoarthritis of the hips due to epiphyseal dysplasia. They frequently require total hip arthroplasty at a relatively young age (30s to 40s).
Question 4404
Topic: 3. Adult Reconstruction (Hip & Knee)
A 28-year-old male with an established diagnosis of Spondyloepiphyseal Dysplasia Tarda (SEDT) presents with severe, debilitating groin pain bilaterally. Conservative management has failed.
Based on the natural history of this disorder, which of the following surgical interventions is he most likely to require?
Correct Answer & Explanation
. Bilateral total hip arthroplasties
Explanation
SEDT frequently leads to severe premature osteoarthritis of the major weight-bearing joints, especially the hips. Joint degeneration often reaches end-stage by the third or fourth decade of life, necessitating total hip arthroplasty.
Question 4405
Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old male undergoes a total hip arthroplasty. Three days post-operatively, he develops fever, erythema, and purulent discharge from the wound. Gram stain reveals Gram-positive cocci. Which of the following components of the innate immune system is primarily responsible for the immediate recognition of pathogen-associated molecular patterns (PAMPs) on these bacteria?
Correct Answer & Explanation
. Toll-like receptors (TLRs)
Explanation
Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) expressed on cells of the innate immune system, such as macrophages and dendritic cells. They recognize conserved molecular patterns on microbes, known as PAMPs, triggering an immediate inflammatory response. T-cell receptors (TCRs) and B-cell receptors (BCRs) are components of the adaptive immune system, recognizing specific antigens. MHC class I molecules present intracellular antigens to CD8+ T cells, while antibodies are products of B cells and part of the humoral adaptive response.
Question 4406
Topic: 3. Adult Reconstruction (Hip & Knee)
A patient with systemic lupus erythematosus (SLE) develops avascular necrosis of the femoral head, a common orthopedic complication. SLE is an autoimmune disease characterized by a loss of self-tolerance. Which of the following T-cell subsets is primarily involved in 'helping' B cells produce autoantibodies and orchestrating the immune response against self-antigens in such conditions?
Correct Answer & Explanation
. T helper cells (CD4+)
Explanation
CD4+ T helper cells are crucial for orchestrating adaptive immune responses. In autoimmune diseases like SLE, specific subsets of CD4+ T helper cells (e.g., Th2 cells) provide co-stimulatory signals and cytokines (like IL-4, IL-5, IL-13) that are essential for B-cell activation, proliferation, and differentiation into plasma cells, leading to the production of pathogenic autoantibodies. CD8+ T cells are cytotoxic, while regulatory T cells suppress immune responses.
Question 4407
Topic: 3. Adult Reconstruction (Hip & Knee)
Periprosthetic joint infection (PJI) often involves bacterial biofilms. How do biofilms primarily contribute to immune evasion and persistent infection in the context of PJI?
Correct Answer & Explanation
. By forming a protective extracellular matrix that shields bacteria from immune cells and antibiotics.
Explanation
Bacterial biofilms are a critical factor in the chronicity and recalcitrance of PJI. They consist of bacterial colonies encased in a self-produced extracellular polymeric substance (EPS) matrix. This matrix acts as a physical barrier, protecting bacteria from host immune defenses (e.g., phagocytosis, complement) and rendering them significantly more resistant to antibiotics. This enables the bacteria to persist and proliferate despite the host's immune response and antimicrobial therapy.
Question 4408
Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old male undergoes a cementless total hip arthroplasty. Four years post-operatively, he presents with sudden onset groin pain and inability to bear weight. Radiographs show a peri-prosthetic fracture around the femoral stem, classified as Vancouver B2. What is the most appropriate management?
Correct Answer & Explanation
. Revision of the femoral stem with a longer, often cemented, stem
Explanation
A Vancouver B2 peri-prosthetic femoral fracture indicates a loose femoral component with adequate bone stock for revision. The most appropriate management is revision of the femoral stem. A longer stem, often cemented or press-fit depending on bone quality and surgeon preference, is typically used to bypass the fracture site by at least two cortical diameters, providing stable fixation and addressing the underlying loosening. Allograft strut may be an adjunct but is not the primary definitive management for the loose component itself.
Question 4409
Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following interventions has the strongest evidence for reducing the risk of heterotopic ossification after total hip arthroplasty?
Correct Answer & Explanation
. Non-steroidal anti-inflammatory drugs (NSAIDs)
Explanation
Both NSAIDs (e.g., indomethacin) and low-dose radiation therapy are highly effective and considered first-line prophylaxis for heterotopic ossification (HO) after total hip arthroplasty. However, NSAIDs are generally preferred due to their ease of administration and lower cost, with comparable efficacy to radiation for most patients. For high-risk patients, a combination or radiation may be used. Bisphosphonates and corticosteroids have not shown consistent efficacy for this indication. Early mobilization is important for general recovery but does not directly prevent HO.
Question 4410
Topic: 3. Adult Reconstruction (Hip & Knee)
A 60-year-old male with a history of chronic alcoholism presents with insidious onset of progressive bilateral hip pain. Radiographs show sclerosis and lucency in the subchondral bone of both femoral heads, without significant joint space narrowing. What is the most likely diagnosis?
Correct Answer & Explanation
. Avascular necrosis (AVN) of the femoral head
Explanation
The combination of chronic alcoholism (a known risk factor), insidious onset of bilateral hip pain, and radiographic findings of subchondral sclerosis and lucency (representing repair and collapse, often with the 'crescent sign' in later stages) in the femoral heads, without significant joint space narrowing initially, is classic for avascular necrosis (AVN) of the femoral head. Osteoarthritis would typically show joint space narrowing and osteophytes. Rheumatoid arthritis would present with inflammatory signs and more diffuse joint involvement.
Question 4411
Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following is considered a relative contraindication to total knee arthroplasty (TKA)?
Correct Answer & Explanation
. Unrealistic patient expectations
Explanation
Unrealistic patient expectations are a relative contraindication to TKA, as they can lead to patient dissatisfaction despite a technically successful surgery. While age over 80, obesity, and nicotine use increase surgical risks, they are generally not absolute contraindications if the patient is otherwise healthy and motivated. Active infection in a remote site is an absolute contraindication, as it significantly increases the risk of periprosthetic joint infection.
Question 4412
Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following is the most common cause of painful total hip arthroplasty revisions after 10 years?
Correct Answer & Explanation
. Osteolysis secondary to polyethylene wear
Explanation
After 10 years, osteolysis secondary to polyethylene wear is the most common cause of aseptic loosening and thus the most frequent indication for revision total hip arthroplasty. The wear debris triggers a foreign body reaction, leading to bone resorption and subsequent implant loosening. While dislocation and infection are important complications, aseptic loosening driven by polyethylene wear-induced osteolysis dominates in the long term.
Question 4413
Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old female with a history of systemic lupus erythematosus (SLE) on chronic high-dose corticosteroids undergoes a total hip arthroplasty (THA) for avascular necrosis. Three months postoperatively, she presents with insidious onset of groin pain, mild swelling, and a low-grade fever (38.1°C). Her erythrocyte sedimentation rate (ESR) is 75 mm/hr and C-reactive protein (CRP) is 60 mg/L. Joint aspiration yields turbid fluid. Synovial fluid analysis shows a white blood cell (WBC) count of 18,000 cells/µL with 78% neutrophils and a single positive alpha-defensin test. Gram stain is negative. Which of the following is the most appropriate next step in confirming the diagnosis of periprosthetic joint infection (PJI)?
Correct Answer & Explanation
. Perform intraoperative frozen section analysis and collect multiple tissue samples for culture.
Explanation
The patient's clinical presentation, elevated inflammatory markers (ESR, CRP), and synovial fluid analysis (WBC count, neutrophil percentage) strongly suggest PJI, even with a negative Gram stain. The positive alpha-defensin test is a highly sensitive and specific marker for PJI. While antibiotics might be considered after cultures are obtained, initiating them immediately would jeopardize the culture results. Repeating aspiration for fungal/mycobacterial cultures is not the initial most definitive step, as the current data points strongly to bacterial PJI. Radionuclide scans are often used in equivocal cases but are less specific than joint aspiration and biopsy in chronic infections. The most definitive diagnostic step, especially when PJI is strongly suspected, is surgical exploration with intraoperative frozen section and collection of multiple periprosthetic tissue samples for microbiology culture. Frozen section analysis can provide rapid intraoperative confirmation of infection, and multiple tissue cultures improve sensitivity for identifying the causative organism. Given the immunosuppressed status due to SLE and corticosteroids, the presentation might be subtle, making robust diagnostic methods critical.
Question 4414
Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old male presents with aseptic loosening of a cemented femoral component following THA performed 15 years prior. Radiographs show significant proximal femoral bone loss classified as Paprosky Type IIIB, with severe cortical thinning and a large defect involving the greater trochanter. There is evidence of a stress riser distal to the stem tip. The patient has good bone stock distally. Which of the following is the most appropriate reconstructive strategy for the femoral side?
Correct Answer & Explanation
. Utilize an extensively porous-coated uncemented stem with diaphyseal fixation.
Explanation
Paprosky Type IIIB femoral defects are characterized by extensive proximal bone loss, severe cortical thinning, and often a stress riser, making standard primary or short stems inadequate. While allograft-prosthesis composites are an option for massive defects, they carry risks of nonunion and infection. Proximal femoral replacement is typically reserved for even more severe defects, such as tumor resection or failed massive allografts. An extensively porous-coated uncemented stem with diaphyseal fixation is the most appropriate choice for Paprosky IIIB defects, as it bypasses the poor proximal bone and achieves stable fixation in the healthy distal diaphysis. Modular distally fixing stems are also a good option, but 'proximal femoral replacement' as an option here might be an overcall. The key is to achieve stable diaphyseal fixation and bypass the proximal defect. Cemented stems are less ideal in this setting due to bone loss and potential for recurrent aseptic loosening.
Question 4415
Topic: 3. Adult Reconstruction (Hip & Knee)
A 55-year-old male undergoes revision THA for recurrent instability. The surgeon implants a modular dual mobility acetabular component. Six months postoperatively, he presents with another dislocation. Radiographs show all components are well-fixed and in good position. Which of the following is the most likely cause of this recurrent dislocation?
Correct Answer & Explanation
. Impaction of the femoral neck on the outer polyethylene liner.
Explanation
Modular dual mobility systems are designed to reduce dislocation risk by providing two articulations: a large diameter articulation between a highly cross-linked polyethylene liner and the metal shell, and a standard articulation between the femoral head and the inner polyethylene liner. The 'jump distance' is significantly increased, making traditional dislocation mechanisms less likely. However, a common mode of failure unique to dual mobility designs (especially modular ones) is impingement of the femoral neck on theouterpolyethylene liner, leading to lever-out of the construct or even dissociation of the head from the inner liner, or the inner liner from the shell. Given that components are well-fixed and in good position, and considering the design, neck-liner impingement (option C) is a well-described cause of recurrent dislocation in dual mobility THAs, leading to lever-out or intra-prosthetic dislocation. Bearing wear is less likely so early. Liner dissociation from the shell is a possibility but neck impingement is a more common initial mechanism leading to issues. Intra-prosthetic dislocation (IPD) is the result, but impingement is often the cause. Femoral component malrotation would typically be addressed as a cause for primary instability.
Question 4416
Topic: 3. Adult Reconstruction (Hip & Knee)
A 70-year-old osteoporotic female presents with a Vancouver B3 periprosthetic femoral fracture around a well-fixed, extensively porous-coated, cementless femoral stem. The fracture extends proximally into the greater trochanter and distally well beyond the stem tip, with significant comminution and poor bone quality. What is the most appropriate treatment strategy?
Correct Answer & Explanation
. Stem removal and revision to a cemented long-stem component.
Explanation
Vancouver B3 fractures are characterized by a loose stem or poor bone quality around a well-fixed stem, making stable fixation of the fracture fragments challenging. Given the extensive comminution, poor bone quality, and the fracture extending beyond the stem tip, the existing stem is compromised even if considered 'well-fixed' initially. ORIF alone (options A and B) is insufficient due to the lack of adequate bone stock for stable fixation and the likely inability to achieve durable construct. Excision arthroplasty is a salvage procedure, not primary treatment for a B3. The presence of significant bone loss and poor quality mandates stem removal and revision to a new stem that can bypass the fracture and achieve stable fixation in healthy bone distally. A cemented long-stem component or a modular distally fixing uncemented stem are both viable options. However, given the osteoporotic bone quality, a cemented long-stem revision often provides more predictable and immediate stability in compromised bone. While a modular distally fixing uncemented stem is also a strong option, the question highlights 'osteoporotic female' and 'poor bone quality', which sometimes sways towards cemented options for immediate stability. Cemented long-stem revision is a well-established strategy for Vancouver B3 fractures where robust fixation is required. Allografting may be needed for severe bone loss, but the primary strategy is stem revision.
Question 4417
Topic: 3. Adult Reconstruction (Hip & Knee)
A 62-year-old male with a Metal-on-Metal (MoM) THA implanted 8 years ago presents with worsening groin and lateral hip pain, an audible 'squeak,' and elevated serum cobalt and chromium levels. MRI arthrogram reveals a large periprosthetic fluid collection (pseudotumor) and extensive synovial thickening consistent with an adverse reaction to metal debris (ARMD). The components appear radiographically well-fixed. What is the most definitive management strategy for this patient?
Correct Answer & Explanation
. Revision THA with exchange of the MoM bearing surface to a ceramic-on-polyethylene or ceramic-on-ceramic coupling.
Explanation
The presence of elevated metal ions, pseudotumor, ARMD on MRI, and persistent symptoms in an MoM THA, even with radiographically well-fixed components, is indicative of progressive adverse tissue reaction. This reaction can lead to significant local tissue damage, osteolysis, and potentially systemic effects. While conservative management, injections, or debridement might provide temporary relief, they do not address the ongoing metal wear and debris generation. The most definitive management is revision THA with exchange of the MoM bearing surface to a non-MoM coupling, such as ceramic-on-polyethylene or ceramic-on-ceramic. This eliminates the source of metal wear debris, preventing further tissue damage and resolving the symptoms. Simply performing debridement and synovectomy without component exchange will not resolve the underlying issue. Regular follow-up is for asymptomatic or mildly symptomatic patients with lower ion levels.
Question 4418
Topic: Total Hip Arthroplasty (THA)
A 60-year-old female undergoes a primary THA via a direct anterior approach. Postoperatively, she complains of numbness and burning pain in the lateral thigh. Sensory examination confirms diminished sensation in the distribution of the lateral femoral cutaneous nerve (LFCN). What is the most appropriate initial management for this iatrogenic complication?
Correct Answer & Explanation
. Prescription of gabapentin or pregabalin and observation.
Explanation
LFCN neuropathy (meralgia paresthetica) is a known complication of the direct anterior approach due to traction or direct injury to the nerve. While surgical exploration is an option for persistent or severe symptoms, theinitialmanagement for most iatrogenic nerve injuries is conservative, focusing on symptom control and allowing for spontaneous recovery. Medications like gabapentin or pregabalin (option B) are commonly used for neuropathic pain. Observation is crucial as many cases resolve spontaneously over weeks to months. NCS/EMG might be useful if symptoms persist or worsen significantly after an initial conservative period to assess the extent of damage but is not the immediate step. Local anesthetic injection can be diagnostic and therapeutic but typically follows medical management. Immediate surgical exploration is generally reserved for severe, progressive deficits or symptoms that fail extensive conservative management, or if there's suspicion of a transection. Therefore, starting with neuropathic pain medication and observation is the most appropriate initial management.
Question 4419
Topic: 3. Adult Reconstruction (Hip & Knee)
A 32-year-old male, a competitive amateur triathlete, presents with bilateral end-stage avascular necrosis of the femoral heads. He requires THA and is concerned about the long-term durability and activity limitations. Considering his age, high activity level, and desire for longevity, which bearing surface combination would be most appropriate to recommend?
Correct Answer & Explanation
. Ceramic-on-ceramic (CoC) bearing.
Explanation
For a young, active patient requiring THA, minimizing wear and maximizing longevity are critical. MoM bearings have largely been abandoned due to concerns about metal ion release, pseudotumor formation, and ARMD. Dual mobility, while excellent for instability, historically used conventional polyethylene (though highly cross-linked variants exist now) and the primary concern for this patient is wear, not instability. Conventional CoP has superior wear characteristics compared to conventional MoP. However, CoC bearings (option C) offer the lowest wear rates and excellent scratch resistance, making them ideal for young, active patients who demand maximum durability and minimal debris generation. While ceramic fractures are a rare but serious complication, the benefits of ultralow wear in a young, active patient generally outweigh this risk for many surgeons. MoP with highly cross-linked polyethylene is also a very good option, but CoC generally has even lower wear, making it the 'most appropriate' for this specific scenario of a highly active young patient prioritizing longevity and low wear. The options provided don't specify highly cross-linked polyethylene for the CoP option, making CoC a stronger choice here, as the question asks 'most appropriate' and lists CoC as a standalone option.
Question 4420
Topic: Total Hip Arthroplasty (THA)
A 67-year-old morbidly obese male (BMI 52 kg/m²) is undergoing primary THA for severe osteoarthritis. What is the most significant specific technical challenge related to his obesity that the surgeon must anticipate and prepare for?
Correct Answer & Explanation
. Difficulty with patient positioning and surgical exposure.
Explanation
Morbid obesity significantly increases the complexity and risks of THA. While all listed options are relevant concerns in obese patients, the 'most significant specific technical challenge' during the actual surgery is often related to patient positioning and achieving adequate surgical exposure. Excess adipose tissue makes standard landmarks difficult to palpate, increases the depth of the surgical field, obscures anatomical structures, and makes retraction challenging. This can lead to longer operative times, increased blood loss, difficulty with component placement, and potential iatrogenic injury. Increased infection risk, DVT, and pain control are all important, but they are general perioperative concerns rather than direct technical challenges of the surgical act itself. Heterotopic ossification is not specifically related to obesity, though overall inflammation might be. Thus, managing the surgical exposure is a predominant intraoperative technical hurdle.
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