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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 217 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 4321

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old active male undergoes total hip arthroplasty with a stiff, large-diameter cobalt-chromium femoral stem. Five years post-op, he develops anterior thigh pain. Radiographs show significant cortical thinning and osteopenia in the proximal femur adjacent to the stem, with no signs of loosening. Which biomechanical phenomenon is most likely responsible for his symptoms and radiographic findings?

. Wear particle-induced osteolysis.
. Stress shielding.
. Periprosthetic infection.
. Disuse osteopenia.
. Taper corrosion.

Correct Answer & Explanation

. Stress shielding.

Explanation

Stress shielding occurs when a stiff, rigid implant (like a large, stiff metallic femoral stem) carries a disproportionate amount of the load normally borne by the bone. According to Wolff's Law, bone remodels in response to mechanical stress. When the stress on the adjacent bone is reduced due to load transfer through the implant, the bone undergoes resorption, leading to cortical thinning and osteopenia, particularly in the calcar region (proximal femur). This phenomenon can manifest as anterior thigh pain. Wear particle-induced osteolysis (Option A) typically presents with more localized, often aggressive, bone loss around the implant, often associated with signs of implant loosening, and usually affects the bone-implant interface more broadly. Periprosthetic infection (Option C) would typically present with inflammatory signs and potentially systemic symptoms. Disuse osteopenia (Option D) is a more generalized bone loss due to lack of activity, not specifically localized to the proximal femur adjacent to the stem. Taper corrosion (Option E) involves material degradation at the head-neck junction, often leading to adverse local tissue reactions, metal ion release, and potential pseudotumor formation, rather than just proximal cortical thinning.

Question 4322

Topic: 3. Adult Reconstruction (Hip & Knee)

A 28-year-old female presents with an osteosarcoma of the distal femur extending into the metaphysis but sparing the articular cartilage. Wide resection is planned. Given her young age and high functional demands, which reconstructive option offers the best long-term durability and resistance to aseptic loosening, while aiming for biological integration?

. Endoprosthetic replacement with a rotating hinge knee
. Allograft-prosthesis composite (APC)
. Vascularized fibula autograft with internal fixation
. Custom 3D-printed titanium mega-prosthesis
. Arthrodesis

Correct Answer & Explanation

. Allograft-prosthesis composite (APC)

Explanation

An allograft-prosthesis composite (APC) for distal femoral reconstruction combines the biological integration of an allograft into the host bone with the functional joint replacement of a prosthesis. This construct offers advantages such as improved long-term durability and resistance to aseptic loosening compared to purely metallic endoprostheses due to biological fixation at the allograft-host interface, which is crucial for younger, active patients. While custom prostheses are effective, the biological integration of an allograft offers a unique advantage for long-term stability. Vascularized fibula autografts are typically insufficient for large structural defects, and arthrodesis is a salvage procedure not suitable for high functional demands.

Question 4323

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old diabetic male with a history of recurrent infections presents with a painful, erythematous, and draining sinus tract overlying his 5-year-old total knee arthroplasty. Cultures from the sinus tract grew methicillin-resistant Staphylococcus aureus (MRSA). Plain radiographs show no evidence of loosening. What is the most appropriate definitive management strategy?

. Long-term suppressive oral antibiotics
. Irrigation and debridement with polyethylene exchange (DAIR)
. Two-stage revision arthroplasty
. One-stage revision arthroplasty
. Arthroscopic debridement

Correct Answer & Explanation

. Two-stage revision arthroplasty

Explanation

A draining sinus tract in the setting of a total joint arthroplasty is considered definitive evidence of a prosthetic joint infection (PJI) extending to the joint, irrespective of imaging findings. For chronic, established infections (typically beyond 3-4 weeks from symptom onset or with a draining sinus tract), particularly with resistant organisms like MRSA, a two-stage revision arthroplasty is the gold standard. This involves removal of all prosthetic components, extensive debridement, antibiotic spacer placement, a period of intravenous antibiotics, and reimplantation after infection eradication is confirmed. DAIR is generally reserved for acute PJIs (less than 3-6 weeks symptoms) without a sinus tract.

Question 4324

Topic: 3. Adult Reconstruction (Hip & Knee)

A total hip arthroplasty surgeon is evaluating a new femoral stem design that utilizes a porous titanium coating applied through electron beam melting (EBM). What is the primary biomechanical advantage of this specific EBM coating over traditional plasma-sprayed coatings for cementless fixation?

. Increased Young's modulus, leading to greater initial stability
. Reduced coefficient of friction, minimizing wear debris
. Enhanced interconnected pore structure, promoting more robust bone ingrowth
. Superior corrosion resistance, prolonging implant lifespan
. Higher ultimate tensile strength, preventing fracture of the stem

Correct Answer & Explanation

. Enhanced interconnected pore structure, promoting more robust bone ingrowth

Explanation

Electron beam melting (EBM) is an additive manufacturing technique that allows for the creation of highly tailored porous structures, often with excellent interconnectivity and uniform pore size distribution. These characteristics are crucial for promoting robust and deep bone ingrowth into the implant surface, which is the cornerstone of successful long-term cementless fixation. The optimized pore morphology and interconnectivity achieved through EBM are often superior for bone ingrowth compared to many traditional plasma-sprayed coatings. Young's modulus relates to stiffness, friction to wear, corrosion resistance to material, and tensile strength to bulk material properties, not specifically the porous coating's primary advantage for ingrowth.

Question 4325

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female presents after a fall with an anterior column and posterior hemitransverse acetabular fracture. She has severe osteoporosis and pre-existing symptomatic osteoarthritis of the ipsilateral hip. She is otherwise healthy, and the fracture pattern involves the weight-bearing dome. Which of the following is the most appropriate definitive management strategy?

. Non-operative management with protected weight-bearing.
. Open reduction and internal fixation (ORIF) of the acetabular fracture.
. Acute total hip arthroplasty (THA) with acetabular reconstruction.
. Skeletal traction followed by delayed ORIF.
. Open reduction with provisional fixation, followed by delayed THA.

Correct Answer & Explanation

. Acute total hip arthroplasty (THA) with acetabular reconstruction.

Explanation

In elderly, osteoporotic patients with pre-existing symptomatic osteoarthritis and an acetabular fracture involving the weight-bearing dome, acute total hip arthroplasty (THA) combined with acetabular reconstruction offers definitive treatment for both the fracture and the arthritic joint. This approach often leads to earlier mobilization, better pain relief, and improved long-term functional outcomes compared to open reduction and internal fixation (ORIF) alone, which may have high failure rates in poor bone quality and often necessitates future THA. Non-operative management is typically reserved for stable, non-displaced fractures without significant involvement of the weight-bearing dome in healthier patients, or when surgical risks outweigh benefits. Delayed options often prolong morbidity.

Question 4326

Topic: Total Hip Arthroplasty (THA)

A 65-year-old male with a history of a cemented total hip arthroplasty (THA) performed 5 years ago presents with his third episode of recurrent posterior dislocation. Radiographs show well-fixed components in satisfactory position. Clinical examination reveals a Trendelenburg gait and weakness in hip abduction. What is the most appropriate next step in surgical management?

. Revision to a larger femoral head.
. Revision to a constrained acetabular liner.
. Revision to a dual mobility acetabular component.
. Abductor repair/reconstruction.
. Femoral stem revision with extended trochanteric osteotomy.

Correct Answer & Explanation

. Revision to a dual mobility acetabular component.

Explanation

For recurrent dislocations in a well-fixed THA where component position is good, a larger femoral head has already failed (or been considered), and abductor insufficiency is present, a dual mobility acetabular component offers enhanced stability. It achieves this by increasing the "jump distance" and allowing for greater range of motion before impingement, thus reducing the risk of dislocation. While abductor repair could be considered if a discrete tear is identified, its success rate can be variable, especially with chronic insufficiency. Dual mobility provides a more mechanically robust solution for persistent instability where soft tissue factors are involved.

Question 4327

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with long-standing rheumatoid arthritis is scheduled for a total knee arthroplasty (TKA). She is currently on Methotrexate and Adalimumab (a TNF-alpha inhibitor). What is the most appropriate perioperative management strategy for her biologic agent to minimize infection risk while controlling disease flare?

. Continue both Methotrexate and Adalimumab through surgery.
. Hold Methotrexate for 1 week preoperatively, continue Adalimumab.
. Hold Adalimumab for 2 half-lives preoperatively and resume after wound healing.
. Hold both Methotrexate and Adalimumab for 1 month preoperatively.
. Switch to a different biologic agent (e.g., Rituximab) preoperatively.

Correct Answer & Explanation

. Hold Adalimumab for 2 half-lives preoperatively and resume after wound healing.

Explanation

For patients on biologic agents like TNF-alpha inhibitors (e.g., Adalimumab) undergoing elective surgery, it is generally recommended to hold the medication for a period equivalent to 1-2 half-lives before surgery to minimize the risk of periprosthetic joint infection (PJI). Adalimumab has a half-life of approximately 10-14 days, so holding it for 2 half-lives (approximately 4 weeks) is a common recommendation, resuming after good wound healing to balance infection risk with disease flare control. Methotrexate, on the other hand, is often continued or held for a shorter period (e.g., 1 week), as its immunosuppressive effect regarding acute infection risk is generally considered less significant than biologics.

Question 4328

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old patient with a history of recurrent hip dislocations following a primary total hip arthroplasty, despite previous revision with a larger femoral head. Patient also has mild dementia and is at high risk for future falls. Which specific type of acetabular component is most indicated in this scenario to provide maximum stability?

. Standard polyethylene liner.
. Highly cross-linked polyethylene liner.
. Constrained acetabular liner.
. Dual mobility acetabular component.
. Revision with an even larger femoral head (if mechanically feasible).

Correct Answer & Explanation

. Constrained acetabular liner.

Explanation

For patients with severe recurrent hip dislocations, especially those with neuromuscular deficits, cognitive impairment (dementia), and a high fall risk, a constrained acetabular liner provides the maximum mechanical resistance to dislocation. This liner mechanically locks the femoral head into the acetabular component, significantly reducing the risk of further dislocations when other methods (like larger heads or even dual mobility components) have failed or are deemed insufficient given the patient's high-risk profile and ongoing risk factors for instability. Dual mobility offers high stability, but a constrained liner is reserved for the most challenging cases demanding absolute resistance to dislocation.

Question 4329

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male undergoes a left total hip arthroplasty for severe osteoarthritis. Postoperatively, he develops a common peroneal nerve palsy characterized by foot drop and diminished sensation over the dorsum of the foot. Which of the following intraoperative factors is most commonly implicated in the etiology of this specific nerve injury during THA?

. Excessive leg lengthening.
. Direct neural compression by retractors.
. Thermal injury from cement polymerization.
. Hematoma formation in the sciatic notch.
. Intraoperative manipulation of a tight sciatic nerve.

Correct Answer & Explanation

. Excessive leg lengthening.

Explanation

Peroneal nerve palsy (foot drop) is a known complication of total hip arthroplasty, and it is a branch of the sciatic nerve. While direct neural compression by retractors (Option B) and hematoma (Option D) can cause sciatic nerve palsies, the most common specific cause of peroneal nerve palsy following THA is excessive leg lengthening (Option A). Lengthening the limb by more than 4 cm (or sometimes even less) can stretch the sciatic nerve, particularly its peroneal division, leading to neuropraxia. This is especially true in patients with pre-existing conditions like spinal stenosis, diabetes, or previous hip surgery. Thermal injury (Option C) is rare with modern cementing techniques and more relevant to direct bone necrosis. Intraoperative manipulation (Option E) is a broader concept, but the specific mechanism for peroneal injury is often stretch from lengthening.

Question 4330

Topic: 3. Adult Reconstruction (Hip & Knee)
A 60-year-old female undergoes revision total knee arthroplasty due to aseptic loosening of the tibial component. Intraoperatively, a Paprosky Type IIIB femoral bone defect is identified. What is the most appropriate reconstruction strategy for this defect?
. Use of bone cement with screws for augmentation.
. Cementless prosthesis with porous coated sleeve or cone, potentially with impaction bone grafting.
. Augmented metal blocks and bone cement, with a constrained implant.
. Standard primary total knee prosthesis with increased cement mantle.
. Autogenous cancellous bone graft alone.

Correct Answer & Explanation

. Cementless prosthesis with porous coated sleeve or cone, potentially with impaction bone grafting.

Explanation

A Paprosky Type IIIB femoral defect in revision TKA implies significant metaphyseal bone loss requiring extensive reconstruction. These defects typically involve more than 50% of the condylar bone loss, often extending into the diaphysis. For such extensive metaphyseal defects, the most appropriate strategy often involves the use of cementless prostheses with porous-coated metaphyseal sleeves or cones, which provide excellent primary stability and long-term biological fixation. Impaction bone grafting can be used to fill defects and promote osteointegration. Metal blocks and bone cement (Option C) are typically used for smaller, contained defects (e.g., Type IIA/B or small III), and not preferred for extensive IIIB defects where long-term biological fixation is desired. Bone cement with screws (Option A) is insufficient for such large defects. Standard primary prosthesis (Option D) is inadequate. Autogenous cancellous bone graft alone (Option E) will resorb and not provide adequate mechanical stability.

Question 4331

Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old male undergoes revision total hip arthroplasty for aseptic loosening of a cemented femoral stem with significant proximal femoral bone loss (Paprosky type IIIB). He has an intact greater trochanter and good abductor function. What is the most appropriate reconstructive option for the femoral side?
. Cemented standard femoral stem.
. Uncemented extensively porous-coated stem.
. Modular tapered fluted titanium stem.
. Femoral head autograft reconstruction with a standard uncemented stem.
. Allograft-prosthesis composite (APC).

Correct Answer & Explanation

. Modular tapered fluted titanium stem.

Explanation

Paprosky type IIIB femoral bone loss indicates severe loss of metaphyseal and diaphyseal bone, making it challenging to achieve stable fixation with standard stems. A cemented standard femoral stem (A) would not provide adequate fixation in a compromised cement mantle and poor bone stock. An uncemented extensively porous-coated stem (B) relies on diaphyseal press-fit and bone ingrowth, which may be difficult to achieve reliably with severe bone loss, particularly if the diaphysis is not a good canal fit. Femoral head autograft (D) is generally not sufficient for type IIIB loss, which often requires structural support beyond what a simple graft can offer. An Allograft-prosthesis composite (E) is a viable and powerful option for severe bone loss (Type III and IV), often providing structural support and allowing for biological fixation; however, it has risks of infection, non-union, and resorption, and is typically reserved for even more severe cases (Type IV or failed Type IIIB where other options are not feasible). For Paprosky type IIIB, a modular tapered fluted titanium stem (C) is often the preferred choice. These stems achieve distal diaphyseal fixation, bypassing the proximal bone defect, and the modularity allows for restoration of leg length, offset, and version. The tapered, fluted design provides excellent rotational stability and press-fit fixation in the distal diaphysis, making it suitable for cases with significant proximal bone loss but an intact distal femoral canal.

Question 4332

Topic: 3. Adult Reconstruction (Hip & Knee)

A 32-year-old professional football player presents with persistent knee pain, swelling, and mechanical symptoms 5 years after a total lateral meniscectomy following a complex tear. Radiographs show early degenerative changes in the lateral compartment, but no significant bone-on-bone arthritis. MRI confirms complete absence of the lateral meniscus. He has failed conservative management and desires to prolong his athletic career. What is the most appropriate surgical recommendation?

. High tibial osteotomy (HTO).
. Lateral unicondylar knee arthroplasty (UKA).
. Total knee arthroplasty (TKA).
. Allograft meniscal transplantation.
. Arthroscopic debridement.

Correct Answer & Explanation

. Allograft meniscal transplantation.

Explanation

The patient is a young, active professional athlete with a history of total meniscectomy, experiencing pain and early degenerative changes without advanced arthritis (no bone-on-bone). He wishes to prolong his career. High tibial osteotomy (A) is typically for unicompartmental osteoarthritis with varus malalignment, aiming to offload the medial compartment, which is not the primary issue here. Lateral unicondylar knee arthroplasty (B) and Total knee arthroplasty (C) are for more advanced, symptomatic arthritis and would end his professional athletic career. Arthroscopic debridement (E) is palliative and unlikely to provide lasting relief.Allograft meniscal transplantation (D)is the most appropriate option. It is indicated in young, active patients with symptomatic meniscal deficiency (prior total meniscectomy), intact articular cartilage (or only early changes), stable ligaments, and proper limb alignment. The goal is to restore the meniscal function (load transmission, shock absorption, joint stability), reduce pain, and potentially delay the progression of osteoarthritis, thereby allowing the patient to continue high-level activities.

Question 4333

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with recurrent dislocations of her right total hip arthroplasty (THA) within 6 months of an uneventful primary surgery. Radiographs show a well-fixed femoral stem and acetabular cup with acceptable inclination (40 degrees) and anteversion (20 degrees). The patient has no history of neurological disorders or cognitive impairment. What is the most likely cause and appropriate next step in management?

. Component malposition; revision of the acetabular component.
. Impacting trochanteric osteotomy.
. Soft tissue imbalance/insufficiency; surgical exploration with potential capsular repair and/or head-neck length adjustment.
. Periprosthetic infection; aspiration and culture.
. Increased offset stem revision.

Correct Answer & Explanation

. Soft tissue imbalance/insufficiency; surgical exploration with potential capsular repair and/or head-neck length adjustment.

Explanation

Given that the radiographs show acceptable component position (inclination 40 deg, anteversion 20 deg are within the safe zone of Lewinnek), the recurrent dislocations are less likely due to malposition. In such cases, soft tissue imbalance or insufficiency (e.g., insufficient tension, incompetent capsule/repair, muscle weakness/denervation) is a more likely cause. Surgical exploration allows for assessment of soft tissue integrity, identification of impingement, and potential for soft tissue repair, revision of head-neck length or use of constrained liners. Aspiration for infection should always be considered for any complication but recurrent dislocation with well-positioned components and no signs of infection usually points to mechanical/soft tissue issues first. Options A, D, and E are less likely or incomplete based on the provided information. Impacting trochanteric osteotomy is not a standard treatment for recurrent dislocations and usually indicated for abductor deficiency or reconstruction.

Question 4334

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old male, 3 months post-total knee arthroplasty (TKA), presents with acute inability to extend his knee and a palpable defect superior to the patella. Radiographs are normal. What is the most likely diagnosis and appropriate management?

. Patellar fracture; non-operative management with extension brace.
. Periprosthetic knee infection; joint aspiration and IV antibiotics.
. Quadriceps tendon rupture; surgical repair.
. Extensor lag due to quadriceps weakness; physiotherapy.
. Patellar component loosening; revision TKA.

Correct Answer & Explanation

. Quadriceps tendon rupture; surgical repair.

Explanation

The clinical presentation of acute inability to extend the knee, a palpable defect superior to the patella, and normal radiographs in a post-TKA patient is pathognomonic for a quadriceps tendon rupture. This is an orthopedic emergency requiring surgical repair. Patellar fracture would be visible on radiographs. Periprosthetic infection is unlikely given the acute mechanical presentation and normal radiographs. Extensor lag due to weakness would not typically present with an acute palpable defect and complete inability to extend. Patellar component loosening would also likely show radiographic changes and usually present with pain or chronic instability rather than acute rupture.

Question 4335

Topic: 3. Adult Reconstruction (Hip & Knee)
A 40-year-old male with a history of chronic alcohol abuse and corticosteroid use for inflammatory bowel disease presents with persistent left hip pain for 3 months. Radiographs show a crescent sign and early flattening of the femoral head, but no significant joint space narrowing. What is the most appropriate non-arthroplasty surgical management for this patient?
. Total hip arthroplasty (THA).
. Core decompression with bone grafting.
. Intertrochanteric osteotomy.
. Hemiarthroplasty.
. Resurfacing arthroplasty.

Correct Answer & Explanation

. Core decompression with bone grafting.

Explanation

The patient's presentation with hip pain, risk factors (alcohol, corticosteroids), a crescent sign, and early flattening of the femoral head indicates osteonecrosis of the femoral head (ONFH) in a pre-collapse or early collapse stage (e.g., Ficat stage II or early III). In this stage, the goal is to prevent further collapse and preserve the native joint. Core decompression with bone grafting (autograft or allograft, often enriched with growth factors or stem cells) is the most appropriate non-arthroplasty surgical management. It aims to reduce intramedullary pressure, improve vascularity, and provide structural support. THA, hemiarthroplasty, and resurfacing arthroplasty are end-stage treatments after significant collapse. Intertrochanteric osteotomy may be considered in specific cases but core decompression is more common for pre-collapse ONFH.

Question 4336

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old male with a history of a left total hip arthroplasty 5 years ago presents with increasing hip pain, fever, and erythema around the incision. Aspiration reveals cloudy fluid. According to the Musculoskeletal Infection Society (MSIS) 2018 criteria, which of the following is considered a major criterion for periprosthetic joint infection (PJI)?

. C-reactive protein (CRP) > 10 mg/L
. Erythrocyte sedimentation rate (ESR) > 30 mm/hr
. Single positive culture of a virulent organism
. Synovial fluid leukocyte count > 3,000 cells/ยตL
. Presence of a sinus tract communicating with the prosthesis

Correct Answer & Explanation

. Presence of a sinus tract communicating with the prosthesis

Explanation

The MSIS 2018 criteria for PJI define the presence of a sinus tract communicating with the prosthesis as a major criterion, which alone is diagnostic for PJI. Other major criteria include: (1) two positive cultures of the same organism or (2) a combination of elevated synovial fluid white blood cell count (WBC), elevated synovial fluid polymorphonuclear neutrophil percentage (PMN%), and positive culture (or positive alpha-defensin). Elevated CRP (>10 mg/L) and ESR (>30 mm/hr) are minor criteria. A single positive culture of a virulent organism can contribute to diagnosis but is not a standalone major criterion. Synovial fluid leukocyte count > 3,000 cells/ยตL is part of the minor criteria and must be combined with PMN% to be considered for diagnosis.

Question 4337

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient with a history of a total knee arthroplasty 2 years prior is diagnosed with chronic periprosthetic joint infection (PJI) caused by Methicillin-resistant Staphylococcus aureus (MRSA). The patient is otherwise healthy. What is the most widely accepted and effective surgical treatment strategy for chronic MRSA PJI?

. Debridement, antibiotics, and implant retention (DAIR)
. Single-stage revision arthroplasty
. Two-stage revision arthroplasty
. Arthrodesis
. Amputation

Correct Answer & Explanation

. Two-stage revision arthroplasty

Explanation

For chronic periprosthetic joint infection (PJI), especially when caused by virulent organisms like MRSA, a two-stage revision arthroplasty is considered the gold standard. This involves complete removal of all prosthetic components, aggressive debridement, placement of an antibiotic-loaded cement spacer, a period of targeted intravenous antibiotic therapy, and then reimplantation of new components after infection eradication is confirmed. DAIR is generally reserved for acute PJI (symptoms <3-4 weeks) or well-fixed implants with less virulent organisms. Single-stage revision has a higher failure rate for chronic PJI. Arthrodesis or amputation are salvage procedures for failed two-stage revisions or severe bone loss/irreversible infection.

Question 4338

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female sustains a fall and experiences pain in her left hip, which underwent total hip arthroplasty 10 years ago. Radiographs reveal a spiral fracture distal to the tip of a well-fixed femoral stem, with no evidence of loosening. According to the Vancouver classification, this fracture would be classified as:

. Type A
. Type B1
. Type B2
. Type B3
. Type C

Correct Answer & Explanation

. Type C

Explanation

The Vancouver classification for periprosthetic femoral fractures categorizes fractures based on location and stem stability: Type A fractures occur in the trochanteric region. Type B fractures occur around the femoral stem; B1 involves a well-fixed stem, B2 involves a loose stem with good bone stock, and B3 involves a loose stem with poor bone stock. Type C fractures occur distal to the tip of the femoral stem. Since the fracture is described as spiral and distal to the tip of a well-fixed stem, it is classified as Vancouver Type C.

Question 4339

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male presents with a painful, swollen right knee 3 years after primary total knee arthroplasty (TKA). Aspiration yields purulent fluid with a WBC count of 95,000 cells/ยตL (92% PMNs) and initial Gram stain showing Gram-positive cocci in clusters. He has no draining sinus tract and good bone stock. The most appropriate surgical management for this periprosthetic joint infection (PJI) is:

. Debridement, antibiotics, and implant retention (DAIR).
. One-stage revision arthroplasty with cement spacers.
. Two-stage revision arthroplasty.
. Long-term suppressive oral antibiotics.
. Knee arthrodesis.

Correct Answer & Explanation

. Two-stage revision arthroplasty.

Explanation

This patient presents with a chronic periprosthetic joint infection (PJI) (symptoms for 3 years post-op, high WBC, purulent aspirate) likely due to S. aureus. For chronic PJI, especially with an established infection over a year after implantation, a two-stage revision arthroplasty is generally considered the gold standard. This involves removal of all prosthetic components, thorough debridement, placement of an antibiotic-impregnated cement spacer, and a prolonged course of intravenous antibiotics, followed by reimplantation once the infection markers normalize. DAIR is typically reserved for acute infections (onset within weeks of surgery or acute hematogenous spread to a well-fixed prosthesis) with sensitive organisms and no loose components. One-stage revision may be considered in very select cases but carries a higher failure rate for established chronic infections. Suppressive antibiotics alone are palliative and not curative for such an active infection. Arthrodesis is a salvage procedure typically reserved for failed two-stage revisions or patients who cannot tolerate further surgery.

Question 4340

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old female sustains a fall and develops a Vancouver B2 periprosthetic fracture around a well-fixed femoral stem after a total hip arthroplasty performed 10 years ago. She has good medical health. What is the most appropriate surgical management?

. Open reduction and internal fixation (ORIF) with plates and screws around the existing stem.
. Revision total hip arthroplasty with a longer, often calcar-loaded, cementless stem.
. Non-weight-bearing and observation, as the stem is well-fixed.
. Placement of cerclage wires alone to stabilize the fracture.
. Girdlestone resection arthroplasty.

Correct Answer & Explanation

. Revision total hip arthroplasty with a longer, often calcar-loaded, cementless stem.

Explanation

A Vancouver B2 periprosthetic fracture involves the femur around a well-fixed stem. The critical issue is that while the original stem is well-fixed, the bone around it is compromised, and the fracture extends beyond the stem. Simply plating around the existing stem (ORIF) would leave the osteoporotic bone susceptible to further fracture or non-union due to the stress riser created by the plate-stem interface. Therefore, the most appropriate management is revision total hip arthroplasty, using a longer, usually cementless stem that bypasses the fracture by at least two cortical diameters, providing robust fixation and stability. This approach addresses both the fracture and the underlying compromised bone. Non-weight-bearing is not suitable for an unstable fracture. Cerclage wires alone provide insufficient stability. Girdlestone is a salvage procedure typically reserved for intractable infection or severe bone loss where other options are not feasible.

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