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 2461
Topic: 3. Adult Reconstruction (Hip & Knee)
A 60-year-old female experiences recurrent posterior dislocations following a primary total hip arthroplasty via a posterior approach. Intraoperative evaluation during revision surgery reveals that the acetabular component is placed in 30 degrees of inclination and 0 degrees of anteversion. What is the optimal target for acetabular component positioning to minimize dislocation risk?
Correct Answer & Explanation
. 40 degrees inclination, 15 degrees anteversion
Explanation
The classic Lewinnek "safe zone" for acetabular cup placement in THA is 40 +/- 10 degrees of inclination and 15 +/- 10 degrees of anteversion. The current cup is severely under-anteverted (0 degrees), predisposing to posterior instability.
Question 2462
Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old female presents with a feeling of her knee "giving way" 2 years after a primary posterior-stabilized total knee arthroplasty. On examination, the knee is stable in extension but opens 12 mm to varus and valgus stress when flexed to 90 degrees. What is the most likely cause of this isolated flexion instability?
Correct Answer & Explanation
. Undersized femoral component
Explanation
Flexion instability in TKA is typically caused by an excessively increased flexion gap relative to the extension gap. Using an undersized femoral component in the anteroposterior dimension reduces the posterior condylar offset, thereby erroneously enlarging the flexion gap.
Question 2463
Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old patient undergoes revision total knee arthroplasty due to persistent pain and effusion 18 months post-primary surgery. Preoperative workup showed ESR 45 mm/hr, CRP 3.2 mg/dL. Knee aspiration yielded 12,000 WBCs with 85% neutrophils. Intraoperatively, tissue cultures are sent. Synovial fluid for alpha-defensin is also sent, yielding a positive result. Given these findings, what is the most appropriate next diagnostic step to confirm or refute a diagnosis of periprosthetic joint infection (PJI)?
Correct Answer & Explanation
. Intraoperative frozen section analysis of periprosthetic tissue
Explanation
The patient's preoperative markers (elevated ESR/CRP, high synovial WBC count, and positive alpha-defensin) are highly suggestive of PJI. Alpha-defensin is particularly sensitive and specific. Intraoperative frozen section analysis of periprosthetic tissue provides a rapid histological assessment (typically ≥5 neutrophils per high-power field) that can confirm the presence of acute inflammation indicative of PJI, allowing the surgeon to make an informed decision regarding the management strategy (e.g., debridement, implant retention vs. two-stage exchange) while still in the operating room. Other options are either redundant (repeat aspiration), less definitive (leukocyte esterase), or typically used in research settings/for confirmation rather than immediate intraoperative decision-making (PCR, D-dimer).
Question 2464
Topic: 3. Adult Reconstruction (Hip & Knee)
A 78-year-old patient with a history of recurrent hip dislocations following a primary total hip arthroplasty (THA) is being considered for revision surgery. The patient has significant cognitive impairment and poor compliance with hip precautions. Which of the following bearing surface configurations would provide the BEST stability against future dislocations, while balancing wear characteristics?
Correct Answer & Explanation
. Dual mobility (DM) polyethylene liner
Explanation
For patients at high risk of recurrent hip dislocation, particularly those with cognitive impairment or poor compliance, dual mobility (DM) articulations offer superior stability. Dual mobility systems combine a small femoral head articulating with a mobile polyethylene liner, which then articulates with a larger metal shell fixed to the acetabulum. This design effectively increases the 'jump distance' and the range of motion before dislocation, significantly reducing dislocation rates compared to conventional THA. While a constrained liner (option B) also enhances stability, it transfers greater stress to the implant-bone interface, increasing the risk of aseptic loosening over time. Large femoral heads (options A, D) improve stability but may not be sufficient for very high-risk patients, and ceramic-on-ceramic bears its own risks. Bipolar hemiarthroplasty (option E) is typically used for femoral neck fractures, not for revision of a THA for instability.
Question 2465
Topic: 3. Adult Reconstruction (Hip & Knee)
A 65-year-old female presents with progressive groin pain and a palpable mass 8 years after a metal-on-metal total hip arthroplasty. Aspiration yields sterile, cloudy fluid. MRI demonstrates a solid and cystic periarticular mass. Which of the following histological findings is most characteristic of this condition?
Correct Answer & Explanation
. Perivascular lymphocytic infiltrate with distinct macrophage response
Explanation
The patient has an Adverse Local Tissue Reaction (ALTR/ALVAL) secondary to metal wear. Histology typically shows a perivascular lymphocytic infiltrate and macrophages laden with metal particles, which is distinctly different from the macrophage and giant cell response seen in polyethylene osteolysis.
Question 2466
Topic: 3. Adult Reconstruction (Hip & Knee)
During a posterior-stabilized total knee arthroplasty, the surgeon notes that the knee is symmetric and stable in extension, but overly tight in flexion, causing the trial femoral component to lift off anteriorly. What is the most appropriate step to balance the knee?
Correct Answer & Explanation
. Downsize the femoral component
Explanation
A knee that is balanced in extension but tight in flexion requires increasing the flexion gap without altering the extension gap. Downsizing the femoral component decreases the posterior condylar offset, selectively enlarging the flexion gap.
Question 2467
Topic: 3. Adult Reconstruction (Hip & Knee)
A 62-year-old female presents with persistent groin pain 6 years after a primary total hip arthroplasty using a metal-on-polyethylene bearing. Laboratory tests reveal a serum cobalt level of 12 ppb and a chromium level of 2 ppb. A MARS MRI shows a thick-walled cystic mass communicating with the joint. What is the most likely source of this patient's pathology?
Correct Answer & Explanation
. Mechanically assisted crevice corrosion at the head-neck taper
Explanation
The presence of elevated cobalt out of proportion to chromium (Co/Cr ratio > 1) in a metal-on-polyethylene THA strongly suggests trunnionosis. This phenomenon is caused by mechanically assisted crevice corrosion at the modular head-neck taper junction, leading to adverse local tissue reactions.
Question 2468
Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old male undergoes a reverse total shoulder arthroplasty for rotator cuff tear arthropathy. Three months post-operatively, he develops sudden severe pain, swelling, and purulent discharge from the incision site. Aspiration confirms a periprosthetic joint infection (PJI). Given the acute nature of the infection and the relatively short time since surgery, what is the MOST appropriate treatment strategy?
Correct Answer & Explanation
. Debridement, antibiotics, and implant retention (DAIR)
Explanation
For acute periprosthetic joint infections (PJI) occurring within 3-4 weeks of surgery, or in early-onset infections (within 3 months) without implant loosening or biofilm maturation, debridement, antibiotics, and implant retention (DAIR) is often a viable option, particularly if the soft tissues are healthy and the organism is susceptible. The goal is to eradicate the infection while preserving the functional implant. Two-stage revision is typically reserved for chronic infections or failed DAIR. Single-stage revision is less common for established infections due to higher failure rates. Long-term suppressive antibiotics are for patients unfit for surgery or with specific organisms. Amputation is a last resort.
Question 2469
Topic: 3. Adult Reconstruction (Hip & Knee)
A 70-year-old male undergoes reverse total shoulder arthroplasty. Two years post-operatively, he presents with progressive shoulder pain, weakness, and limited elevation. Radiographs show subsidence of the humeral component and glenoid bone loss around the baseplate. The inflammatory markers (ESR, CRP) are mildly elevated. What is the MOST likely cause of his symptoms?
Correct Answer & Explanation
. Aseptic loosening of components
Explanation
Progressive pain, weakness, and limited elevation after a reverse total shoulder arthroplasty, along with radiographic evidence of component subsidence and glenoid bone loss, are classic signs of aseptic loosening. While periprosthetic joint infection (PJI) can also cause pain and loosening, the 'mildly elevated' inflammatory markers are more consistent with aseptic loosening than active infection (where markers are typically significantly elevated). Rotator cuff tears are not relevant after rTSA (the deltoid powers elevation). Impingement syndrome is less common with rTSA geometry. Axillary nerve neuropraxia would typically present earlier post-operatively with deltoid weakness and sensory changes.
Question 2470
Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old female with advanced rheumatoid arthritis undergoes a primary linked Total Elbow Arthroplasty (TEA). To ensure implant longevity, which of the following is a mandatory permanent postoperative restriction?
Correct Answer & Explanation
. Lifting restriction of no more than 1 pound repetitively and 5 pounds for single events
Explanation
To prevent catastrophic aseptic loosening and polyethylene wear, patients with a Total Elbow Arthroplasty are strictly advised to adhere to a lifetime lifting restriction. This is typically limited to 1 pound repetitively and 5 to 10 pounds for single events.
Question 2471
Topic: 3. Adult Reconstruction (Hip & Knee)
What is the primary vascular supply to the scaphoid bone?
Correct Answer & Explanation
. Branches from the radial artery entering distally
Explanation
The scaphoid bone has a unique and precarious blood supply, primarily from branches of the radial artery that enter distally. These vessels travel proximally, supplying the majority of the bone, including the proximal pole. This distal entry and retrograde flow explain why the proximal pole is particularly vulnerable to avascular necrosis following a fracture, as its blood supply can be disrupted.
Question 2472
Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old female presents after a ground-level fall, complaining of hip pain. Radiographs reveal a Garden Type III femoral neck fracture. She is otherwise fit and well with no significant comorbidities. Which of the following is the most appropriate management strategy?
Correct Answer & Explanation
. Total hip arthroplasty (THA).
Explanation
A Garden Type III femoral neck fracture is a displaced fracture. In an active, otherwise healthy 72-year-old, total hip arthroplasty (THA) is often favored over hemiarthroplasty, especially in patients with pre-existing arthritis or good functional demands. While hemiarthroplasty is an option for displaced femoral neck fractures in the elderly, THA generally provides better long-term functional outcomes and reduces the need for revision surgery compared to hemiarthroplasty in active patients. ORIF with cannulated screws has a high risk of avascular necrosis and non-union in displaced fractures in this age group. Non-operative management is reserved for non-displaced or impacted fractures in very frail patients. DHS is not suitable for femoral neck fractures.
Question 2473
Topic: 3. Adult Reconstruction (Hip & Knee)
A 55-year-old male with a history of chronic alcoholism presents with a displaced femoral neck fracture. He is deemed unfit for total hip arthroplasty due to significant medical comorbidities. Which of the following is the most appropriate surgical option?
Correct Answer & Explanation
. Hemiarthroplasty.
Explanation
For a displaced femoral neck fracture in an elderly patient with significant medical comorbidities who is deemed unfit for a more extensive procedure like THA, hemiarthroplasty is often the preferred choice. It offers immediate stability, allows for early mobilization, and has a lower operative time and complexity compared to THA. ORIF with cannulated screws in displaced femoral neck fractures in older patients carries a high risk of avascular necrosis and non-union, which would necessitate revision surgery in a frail patient. Non-operative management leads to prolonged bed rest and its associated complications. THA is typically for more active or healthier patients. DHS is not used for femoral neck fractures.
Question 2474
Topic: 3. Adult Reconstruction (Hip & Knee)
A 30-year-old female presents with a chronic, symptomatic non-union of the scaphoid after 12 months. Radiographs show sclerosis and cystic changes at the fracture site, with no signs of avascular necrosis of the proximal pole. What is the most appropriate surgical management?
Correct Answer & Explanation
. Non-vascularized bone graft with internal fixation.
Explanation
For a chronic scaphoid non-union without avascular necrosis of the proximal pole, a non-vascularized bone graft (often from the distal radius or iliac crest) combined with internal fixation (typically a headless compression screw) is the standard surgical management. The bone graft provides osteoconductive and osteoinductive properties, promoting union, while the screw provides stable compression. Vascularized bone grafts are reserved for cases with avascular necrosis of the proximal pole or failed non-vascularized grafts. Continued cast immobilization is unlikely to succeed after 12 months. Percutaneous screw fixation is for acute, non-displaced fractures. Proximal row carpectomy is a salvage procedure for severe wrist arthritis or failed multiple procedures.
Question 2475
Topic: 3. Adult Reconstruction (Hip & Knee)
A 70-year-old male falls and sustains a femoral neck fracture. He has a history of Parkinson's disease, severe osteoporosis, and is minimally ambulatory with a walker. Radiographs show a displaced Garden Type IV femoral neck fracture. What is the most appropriate surgical management?
Correct Answer & Explanation
. Hemiarthroplasty.
Explanation
For an elderly patient with significant comorbidities (Parkinson's, severe osteoporosis, minimally ambulatory) and a displaced femoral neck fracture, hemiarthroplasty is generally the most appropriate surgical option. It offers immediate stability, allowing for early mobilization and weight-bearing, which is crucial to prevent complications of prolonged bed rest in this frail population. It is a less extensive procedure than THA and associated with lower dislocation rates in patients with cognitive impairment. ORIF has a high failure rate (non-union, avascular necrosis) in displaced fractures in elderly patients with osteoporosis. THA is typically reserved for more active patients or those with pre-existing arthritis. Non-operative management is associated with high mortality and morbidity. DHS is not used for femoral neck fractures.
Question 2476
Topic: 3. Adult Reconstruction (Hip & Knee)
The primary cause of aseptic loosening in total knee arthroplasty (TKA) is most commonly attributed to:
Correct Answer & Explanation
. Wear particles inducing osteolysis
Explanation
Aseptic loosening is the most common long-term complication leading to revision surgery in total knee arthroplasty (TKA) and other total joint replacements. The primary mechanism underlying aseptic loosening is the host's inflammatory response to microscopic wear particles generated from the bearing surfaces (typically polyethylene, but also metal or ceramic). These particles (e.g., UHMWPE debris) are phagocytosed by macrophages and other immune cells in the periprosthetic tissues, triggering a chronic inflammatory cascade that results in local bone resorption (osteolysis) around the implant, ultimately leading to loss of fixation. While the other options can contribute to implant failure, osteolysis due to wear particles is the predominant mechanism for aseptic loosening.
Question 2477
Topic: 3. Adult Reconstruction (Hip & Knee)
A 65-year-old active female undergoes total hip arthroplasty with a highly cross-linked polyethylene (HXLPE) liner. Which of the following describes a biomechanical trade-off resulting from the irradiation and remelting process used to create HXLPE compared to conventional polyethylene?
Correct Answer & Explanation
. Decreased ultimate tensile strength and fatigue resistance
Explanation
Irradiation creates free radicals that cross-link the polymer, drastically reducing wear. However, the subsequent remelting process used to eliminate remaining free radicals decreases the material's crystallinity, thereby reducing its ultimate tensile strength, yield strength, and fatigue resistance.
Question 2478
Topic: 3. Adult Reconstruction (Hip & Knee)
In a patient with aseptic loosening 15 years after a cemented total hip arthroplasty, what is the primary cell responsible for the periprosthetic osteolysis?
Correct Answer & Explanation
. Macrophage
Explanation
Aseptic loosening is primarily driven by macrophage activation secondary to phagocytosis of particulate wear debris. This leads to the release of inflammatory cytokines that stimulate osteoclastic bone resorption.
Question 2479
Topic: 3. Adult Reconstruction (Hip & Knee)
During a total knee arthroplasty for a patient with a severe, fixed valgus deformity, standard sequential lateral release is often required. Utilizing an outside-in technique (pie-crusting), which structure is typically released first?
Correct Answer & Explanation
. Iliotibial band
Explanation
In a fixed valgus knee, the iliotibial band (ITB) is typically the most contracted structure in extension and is released first. Further releases may involve the LCL or popliteus depending on flexion and extension gap balancing.
Question 2480
Topic: 3. Adult Reconstruction (Hip & Knee)
A 65-year-old female undergoes a total hip arthroplasty utilizing a ceramic-on-ceramic bearing surface. At her 1-year follow-up, she complains of an audible squeaking sound during ambulation. What is the most likely biomechanical etiology for this phenomenon?
Correct Answer & Explanation
. Stripe wear resulting from edge loading
Explanation
Squeaking in ceramic-on-ceramic THA is heavily associated with edge loading, often due to cup malpositioning (such as excessive steepness). This leads to localized stripe wear on the ceramic head, altering fluid film lubrication and generating noise.
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