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 201
Topic: 3. Adult Reconstruction (Hip & Knee)
A 44-year-old man has a 2-year history of pain in his hallux. The pain is accompanied by limited range of motion, pain on passive dorsiflexion of the hallux, and difficulty with athletic activities. Radiographs demonstrate that the plantar two-thirds of the joint is normal, with osteophytes of the dorsal surface of the joint. He has been unsuccessful with shoe wear modifications, and he requests surgery. The ideal procedure for him would be:
Correct Answer & Explanation
. C heilectomy of the hallux
Explanation
Preservation of the joint and maintaining range of motion are important to any active individual. Any procedure, such as resection or implant arthroplasty, is contraindicated in this age group. Arthritis has not progressed to the degree that arthrodesis is necessary.
Question 202
Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following total hip arthroplasty (THA) bearing surface combinations demonstrates the lowest volumetric wear rate in laboratory simulator studies?
Correct Answer & Explanation
. Ceramic on ceramic
Explanation
Ceramic-on-ceramic bearing surfaces exhibit the lowest volumetric wear rates of all THA bearing options. However, they carry specific risks, such as component fracture and squeaking.
Question 203
Topic: 3. Adult Reconstruction (Hip & Knee)
The primary blood supply to the adult femoral head is derived predominantly from which of the following vessels?
Correct Answer & Explanation
. Medial femoral circumflex artery
Explanation
The medial femoral circumflex artery (MFCA) provides the primary blood supply to the adult femoral head via its lateral epiphyseal branches. Injury to this vessel significantly increases the risk of avascular necrosis.
Question 204
Topic: 3. Adult Reconstruction (Hip & Knee)
During a total knee arthroplasty (TKA), internal rotation of the femoral component relative to the epicondylar axis will most likely result in which of the following complications?
Correct Answer & Explanation
. Lateral patellar maltracking
Explanation
Internal rotation of the femoral component laterally displaces the trochlear groove relative to the extensor mechanism, leading to lateral patellar maltracking and potential dislocation. It also tightens the medial compartment in flexion.
Question 205
Topic: 3. Adult Reconstruction (Hip & Knee)
When counseling a 40-year-old highly active patient regarding total hip arthroplasty (THA), which of the following bearing surface combinations should be noted as having the lowest linear and volumetric wear rates?
Correct Answer & Explanation
. Ceramic on ceramic
Explanation
Ceramic-on-ceramic articulations exhibit the lowest linear and volumetric wear rates among all THA bearing couples. Despite excellent wear characteristics, they carry unique risks such as "squeaking" and the potential for catastrophic component fracture.
Question 206
Topic: 3. Adult Reconstruction (Hip & Knee)
A 70-year-old female sustains a posterior dislocation of her total hip arthroplasty 4 weeks post-surgery. Her index surgical approach was posterior. To minimize the risk of recurrent posterior dislocation during a planned revision, which component position adjustment is most appropriate?
Correct Answer & Explanation
. Increase acetabular cup anteversion
Explanation
Posterior THA instability is commonly associated with inadequate anteversion of the acetabular cup. Increasing cup anteversion and utilizing a larger diameter femoral head can effectively enhance posterior stability.
Question 207
Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old male presents with worsening left groin and thigh pain 15 years after a primary THA. His initial radiographs show significant superior migration of the acetabular component with superior pole osteolysis and a wide lucent line at the bone-cement interface. The femoral component shows 8mm subsidence with lucencies in Gruen zones 1, 2, 6, and 7, and pedestal formation in Gruen zone 4. Laboratory investigations reveal an ESR of 38 mm/hr and a CRP of 12 mg/L. Joint aspiration yields a WBC count of 850 cells/ยตL with 68% PMNs, and cultures are negative. Given these findings, which of the following is the MOST likely primary diagnosis?
Correct Answer & Explanation
. Aseptic Loosening with Osteolysis
Explanation
Correct Answer: CThe patient's presentation, imaging, and laboratory findings are most consistent with aseptic loosening with osteolysis. The insidious onset of pain, progressive limp, and radiographic evidence of component migration, wide lucent lines (>2mm), pedestal formation, and extensive osteolysis (superior acetabular pole, proximal femur) are classic signs of aseptic loosening. While the ESR (38 mm/hr) and CRP (12 mg/L) are mildly elevated, and the aspiration WBC count (850 cells/ยตL) and PMN percentage (68%) are borderline, the absence of systemic signs of infection (fever, chills), negative bacterial cultures after 7 days, and negative alpha-defensin strongly argue against PJI as the primary diagnosis. The case explicitly states that PJI was considered low probability. Periprosthetic fracture was ruled out by the CT scan. Lumbar spine radiculopathy might cause groin pain, but it would not explain the overt mechanical symptoms, limb shortening, or the extensive radiographic signs of implant failure. Stress shielding is present but is a consequence of the implant and not the primary cause of the debilitating pain and mechanical failure; disuse atrophy is also a secondary finding.
Question 208
Topic: Total Hip Arthroplasty (THA)
Based on the CT scan findings described in the case, the acetabular bone defect is classified as Paprosky Type IIIA. Which of the following best describes the key characteristics of a Paprosky Type IIIA acetabular defect?
Correct Answer & Explanation
. Extensive superior segmental and cavitary bone loss, with a deficient superior dome and often medial wall perforation.
Explanation
The case explicitly states the CT scan confirmed a Paprosky Type IIIA defect, characterized by 'extensive superior segmental and cavitary bone loss, with a deficient superior dome and medial wall perforation.' This classification indicates significant loss of more than 50% of host bone stock in the superior region, making primary cup fixation challenging. Option A describes a less severe defect, often Paprosky Type IIA or IIB. Option B is incorrect as Type IIIA involves significant segmental loss, typically more than 50%. Option D describes a Paprosky Type IV defect, which is more severe than IIIA, involving complete loss of host bone. Option E describes a Paprosky Type I defect, which is the least severe. Therefore, extensive superior segmental and cavitary bone loss with a deficient superior dome and often medial wall perforation accurately defines a Paprosky Type IIIA defect as described in the case.
Question 209
Topic: Total Hip Arthroplasty (THA)
The CT scan also confirmed a Paprosky Type IIB femoral bone defect. Considering this classification, what is the most appropriate surgical strategy for femoral reconstruction in this patient?
Correct Answer & Explanation
. A long, modular, uncemented femoral stem designed for diaphyseal fixation, bypassing proximal bone loss.
Explanation
Correct Answer: CA Paprosky Type IIB femoral defect is characterized by proximal femoral bone loss with a widened femoral canal and a deficient metaphysis, but with an intact distal diaphysis capable of providing stable fixation. The case specifically states that templating favored 'a long, proximally coated, distally fixing modular revision stem' to 'bypass the proximal bone loss and achieve diaphyseal fixation.' Option A (short, proximally coated stem) is suitable for Paprosky Type I or IIA defects where the metaphysis is largely intact. Option B (cemented stem) is generally avoided in revision THA with significant bone loss due to concerns about cement mantle integrity and long-term fixation, especially when the canal is widened. Option D (proximal femoral replacement) is reserved for more severe defects (Paprosky Type IV) or tumor resections. Option E (non-operative management) is inappropriate given the patient's debilitating pain and progressive mechanical failure. Therefore, a long, modular, uncemented femoral stem designed for diaphyseal fixation, bypassing the area of proximal bone loss, is the correct strategy.
Question 210
Topic: 3. Adult Reconstruction (Hip & Knee)
The patient's pre-operative workup included a dedicated CT scan of the pelvis and bilateral hips with thin cuts and metal artifact reduction protocols. What is the primary reason for obtaining this specific imaging study in a complex revision THA case like this?
Correct Answer & Explanation
. To precisely define the extent and morphology of bone defects, delineate osteolytic lesions, and plan for component removal and reconstruction.
Explanation
Correct Answer: CThe case explicitly states the purpose of the CT scan: 'To precisely define the extent and morphology of bone defects, delineate osteolytic lesions, assess implant version and inclination, and plan for component removal and reconstruction.' While a CT can show soft tissue changes (Option B) and HO (Option E), and indirectly suggest neurovascular proximity (Option D), its primary role in complex revision THA, especially with metal artifact reduction, is to overcome the limitations of plain radiographs in visualizing bone loss and implant position due to metallic glare. It is not definitive for ruling out PJI (Option A), which relies more on laboratory markers and aspiration. Therefore, precisely defining bone defects and planning reconstruction is the most critical reason.
Question 211
Topic: Total Hip Arthroplasty (THA)
For the acetabular reconstruction in this Paprosky Type IIIA defect, a modular trabecular metal dome augment was selected. What is the primary advantage of using such an augment in this specific scenario?
Correct Answer & Explanation
. To provide structural support for the deficient superior dome, restore the hip center, and allow for stable screw fixation into host bone.
Explanation
The case describes a Paprosky Type IIIA defect with extensive superior segmental and cavitary bone loss, with a deficient superior dome. The rationale for augment selection states: 'This construct allows for immediate stability through screw fixation in healthy host bone (ilium/ischium) and biological ingrowth, while the augment addresses the significant superior segmental bone loss, providing scaffolding and restoring the hip center.' Option A is incorrect; while it might increase the overall construct size, the primary purpose is not just diameter but structural support. Option B is incorrect; while medial wall perforation is a concern, a dome augment primarily addresses superior defects. Option D is incorrect; augments do not directly reduce heterotopic ossification. Option E is incorrect; a larger femoral head (36 mm) was chosen to maximize jump distance, not a smaller one. Therefore, providing structural support for the deficient superior dome, restoring the hip center, and allowing for stable screw fixation into host bone is the primary advantage.
Question 212
Topic: Total Hip Arthroplasty (THA)
Following the successful removal of the femoral component and cement, the surgeon performed cancellous allograft bone chip impaction grafting into the proximal femur. What is the main objective of this technique in the context of a Paprosky Type IIB femoral defect?
Correct Answer & Explanation
. To reconstruct the metaphyseal bone loss, provide a biological scaffold for bone healing, and support trochanteric reattachment.
Explanation
Correct Answer: CThe case states that for the Paprosky IIB defect, 'cancellous allograft bone chips were carefully impacted into the proximal femur around a sizing trial, creating a contained bed for the modular stem. This technique provides mechanical support and promotes biological integration.' It further clarifies that this was done 'to address the proximal femoral bone loss and provide support for the proximal stem and greater trochanteric reattachment.' Option A is incorrect as a modular, uncemented stem was used. Option B is incorrect as a long, distally fixing stem was used, and impaction grafting provides biological support, not necessarily immediate rigid fixation for a short stem. Option D is incorrect; impaction grafting is primarily for bone reconstruction, not stress shielding prevention. Option E is incorrect; while filling dead space can be beneficial, the primary objective is bone reconstruction and biological integration, not infection prevention. Therefore, reconstructing the metaphyseal bone loss, providing a biological scaffold for bone healing, and supporting trochanteric reattachment is the main objective.
Question 213
Topic: 3. Adult Reconstruction (Hip & Knee)
During the component removal phase of this complex revision, the removal of the remaining cement mantle was identified as the most challenging part. Which of the following 'pearls' from the case study is most critical to avoid a significant pitfall during this step?
Correct Answer & Explanation
. Meticulous removal of all residual cement from the femoral canal using specialized tools while preserving host bone stock.
Explanation
Correct Answer: CThe 'Pearls & Pitfalls' section emphasizes: 'Preserve Bone Stock: This is paramount. Use specialized instruments for cement and implant removal (high-speed burrs, ultrasonic cement removal, specific extractors) with constant irrigation and cooling. Avoid iatrogenic fractures.' And 'Suboptimal Cement Removal: Retained cement can compromise primary fixation of new uncemented components and potentially lead to further osteolysis.' Therefore, meticulous removal of all residual cement from the femoral canal using specialized tools while preserving host bone stock is the most critical pearl. Option A (prioritizing speed) increases the risk of iatrogenic fracture. Option B (using only standard osteotomes) is insufficient for complex cement removal. Option D (leaving small fragments) is a pitfall as retained cement can compromise fixation and lead to osteolysis. Option E (relying solely on visual inspection) is insufficient; tactile feedback and specialized tools are needed.
Question 214
Topic: 3. Adult Reconstruction (Hip & Knee)
Given the extensive soft tissue dissection and the performance of a greater trochanteric osteotomy during this complex revision THA, which of the following post-operative complications is the patient at a significantly increased risk for, and what prophylaxis should be considered?
Correct Answer & Explanation
. Heterotopic Ossification (HO); prophylaxis with NSAIDs or radiotherapy.
Explanation
Correct Answer: CThe 'Pearls & Pitfalls' section specifically lists: 'Heterotopic Ossification (HO): A common complication after revision THA, especially with extensive soft tissue dissection or trochanteric osteotomy. Prophylaxis (NSAIDs or radiotherapy) should be considered.' Option A (Sciatic nerve palsy) is a risk during surgery, but prophylaxis is meticulous dissection and protection, not nerve blocks. Option B (Recurrent dislocation) is a risk, but prophylaxis involves careful component positioning, soft tissue balancing, and hip precautions, not typically bracing as a primary prophylactic measure. Option D (DVT) is a risk, but prophylaxis involves LMWH/Factor Xa inhibitors and early mobilization, not ambulation only. Option E (PJI) is a concern, but long-term oral antibiotics are not standard prophylaxis for all revision THAs; they are used for treatment or in high-risk cases. Therefore, Heterotopic Ossification with NSAID or radiotherapy prophylaxis is the correct answer.
Question 215
Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old female presents with severe groin pain 10 years after a total hip arthroplasty. Radiographs show a transverse fracture through the acetabulum with a loose cup and inferior hemi-pelvis rotation. Which reconstruction method is most appropriate for a chronic pelvic discontinuity with severe bone loss?
Correct Answer & Explanation
. Cup-cage construct or custom triflange component
Explanation
Chronic pelvic discontinuity with severe bone loss is best treated with highly porous metal options like a cup-cage construct, custom triflange, or distraction techniques. These methods achieve stable fixation across the defect and allow for biologic ingrowth.
Question 216
Topic: Total Hip Arthroplasty (THA)
When performing an extended trochanteric osteotomy (ETO) for femoral stem removal during revision THA, what is the recommended length of the osteotomy to ensure adequate healing and avoid diaphyseal fracture?
Correct Answer & Explanation
. 10-15 cm, maintaining at least a 5 cm intact diaphyseal bridge distal to the stem
Explanation
An ETO should typically be 10-15 cm in length, leaving at least 1-2 diaphyseal diameters (approximately 5-6 cm) of intact bone distal to the tip of the existing stem. This prevents fracture and provides adequate fixation for the new stem.
Question 217
Topic: Total Hip Arthroplasty (THA)
A patient requires revision of a loose cemented femoral stem. Radiographs demonstrate complete loss of metaphyseal cancellous bone and diaphyseal bone loss down to the isthmus, with less than 4 cm of intact diaphyseal bone remaining for fixation. What is the Paprosky femoral defect classification?
Correct Answer & Explanation
. Type IIIB
Explanation
Paprosky Type IIIB defects are characterized by severe metaphyseal and diaphyseal bone loss with less than 4 cm of intact diaphyseal isthmus available for fixation. They often require a fully coated cylindrical stem, modular fluted tapered stem, or allograft-prosthesis composite.
Question 218
Topic: Total Hip Arthroplasty (THA)
In revision THA, a "jumbo" acetabular cup is often used to achieve stability in Paprosky Type II defects. Which of the following defines a jumbo cup?
Correct Answer & Explanation
. >62 mm in females and >66 mm in males
Explanation
A jumbo cup is traditionally defined as >62 mm in females and >66 mm in males. It allows for a large surface area of porous coating to achieve biologic fixation in the presence of mild to moderate bone loss.
Question 219
Topic: Total Hip Arthroplasty (THA)
A 75-year-old female with a history of recurrent dislocations following primary THA is undergoing revision surgery. The abductor mechanism is noted to be severely deficient and fatty infiltrated on preoperative MRI. Which of the following components offers the most reliable stability?
Correct Answer & Explanation
. Dual mobility construct or constrained liner
Explanation
In the setting of severe abductor deficiency and recurrent instability, standard liners carry a high failure rate. A constrained liner or a dual mobility articulation provides the highest degree of mechanical stability.
Question 220
Topic: 3. Adult Reconstruction (Hip & Knee)
A 60-year-old male presents with groin pain 7 years after a metal-on-polyethylene THA. Serum cobalt levels are elevated (10 ppb) while chromium is mildly elevated (2 ppb). Aspiration reveals negative cultures but elevated WBC with high mononuclear cells. MRI shows a pseudotumor. What is the most likely cause?
An elevated cobalt-to-chromium ratio in a metal-on-polyethylene THA, combined with a pseudotumor and negative cultures, is highly suggestive of trunnionosis. This represents mechanically assisted crevice corrosion at the head-neck junction.
Test Yourself
Switch to an interactive, timed exam simulation to truly master this topic.