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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 14 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 261

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female undergoes a total hip arthroplasty using a highly cross-linked polyethylene (HXLPE) liner. Which of the following best describes a mechanical tradeoff resulting from the irradiation process used to manufacture HXLPE?

. Decreases free radicals
. Increases crystallinity
. Decreases adhesive wear
. Increases ultimate tensile strength
. Decreases fatigue strength

Correct Answer & Explanation

. Decreases fatigue strength

Explanation

Irradiation of polyethylene increases cross-linking, which significantly improves wear resistance. However, it negatively affects bulk mechanical properties, leading to decreased ultimate tensile strength and decreased fatigue strength.

Question 262

Topic: 3. Adult Reconstruction (Hip & Knee)

To minimize the risk of iatrogenic avascular necrosis of the femoral head during a standard posterior hip approach, which of the following short external rotators must be preserved to protect the ascending branch of the medial femoral circumflex artery (MFCA)?

. Piriformis
. Obturator internus
. Superior gemellus
. Obturator externus
. Inferior gemellus

Correct Answer & Explanation

. Obturator externus

Explanation

The obturator externus tendon protects the ascending branch of the medial femoral circumflex artery (MFCA) as it courses posterior to the femoral neck. Transecting this tendon increases the risk of vascular compromise to the femoral head.

Question 263

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with groin pain 3 years after a primary total hip arthroplasty utilizing a metal-on-polyethylene bearing with a titanium femoral stem and a cobalt-chromium head. Radiographs show no loosening, but an MRI with metal artifact reduction shows a solid pseudotumor adjacent to the joint. Blood tests reveal elevated serum cobalt levels but normal chromium levels. What is the most likely etiology of her symptoms?

. Polyethylene wear
. Trunnionosis
. Unrecognized periprosthetic joint infection
. Aseptic loosening
. Impingement of the iliopsoas tendon

Correct Answer & Explanation

. Trunnionosis

Explanation

Trunnionosis refers to mechanically assisted crevice corrosion at the head-neck junction. In non-metal-on-metal bearings, it typically presents with an adverse local tissue reaction (pseudotumor) and elevated serum cobalt levels that are disproportionately higher than chromium.

Question 264

Topic: 3. Adult Reconstruction (Hip & Knee)

A 10-year-old boy with a distal femoral osteosarcoma is undergoing limb salvage with a planned expandable endoprosthesis. What is the primary advantage of using an expandable endoprosthesis over a conventional fixed-length endoprosthesis in this patient?

. Lower risk of deep infection.
. Superior bone integration and reduced aseptic loosening.
. Ability to achieve limb lengthening to compensate for growth.
. Elimination of the need for future revision surgeries.
. Reduced cost and shorter operative time.

Correct Answer & Explanation

. Ability to achieve limb lengthening to compensate for growth.

Explanation

Correct Answer: CExplanation:The primary advantage of an expandable endoprosthesis (also known as a growing prosthesis) in a skeletally immature patient is its ability to be lengthened over time. This feature allows the reconstructed limb to keep pace with the growth of the contralateral limb, thereby preventing or minimizing significant limb length discrepancy as the child grows. This is crucial for maintaining function and avoiding multiple complex lengthening procedures in the future.A. Lower risk of deep infection:Expandable prostheses are complex and do not inherently have a lower infection risk; in fact, their complexity might sometimes increase it.B. Superior bone integration and reduced aseptic loosening:While implant design aims for good integration, expandability itself doesn't guarantee superior integration or reduced loosening compared to fixed prostheses, which are also prone to these issues.D. Elimination of the need for future revision surgeries:Expandable prostheses have a finite lifespan and are still subject to mechanical failure, infection, and loosening, often requiring revision surgeries in the long term.E. Reduced cost and shorter operative time:Expandable prostheses are typically more complex and expensive than fixed-length prostheses, and their implantation may not necessarily be shorter.

Question 265

Topic: Total Hip Arthroplasty (THA)

During a posterior approach to the knee for open reattachment of a PCL avulsion, the popliteal vessels are displaced laterally. Which of the following neurovascular structures is most directly at risk of injury during this maneuver, particularly if ligation of the middle geniculate and superior medial geniculate vessels is required?

. Common peroneal nerve
. Sural nerve
. Tibial nerve
. Small saphenous nerve
. Popliteal artery

Correct Answer & Explanation

. Popliteal artery

Explanation

Correct Answer: EThe case states, "Popliteal vessels are displaced laterally and this usually requires ligation of middle geniculate and superior medial geniculate vessels." The middle and superior medial geniculate vessels are branches of the popliteal artery. Therefore, the maneuver of displacing the popliteal vessels and ligating these specific branches directly involves the popliteal artery, placing it at the most direct risk of injury during this particular step. While the tibial nerve (which lies posterior to the popliteal vein) and other nerves (common peroneal, sural, small saphenous) are generally at risk during a posterior approach, the question specifically highlights the manipulation of the popliteal vessels and ligation of its branches, making the popliteal artery the most pertinent answer in this context.

Question 266

Topic: Total Hip Arthroplasty (THA)

When performing a posterior approach to the knee, the candidate describes the relative anatomical positions of key neurovascular structures in the popliteal fossa. From deepest to most superficial, what is the correct order of the popliteal artery, popliteal vein, and tibial nerve?

. Popliteal artery, Popliteal vein, Tibial nerve
. Tibial nerve, Popliteal vein, Popliteal artery
. Popliteal vein, Popliteal artery, Tibial nerve
. Popliteal artery, Tibial nerve, Popliteal vein
. Tibial nerve, Popliteal artery, Popliteal vein

Correct Answer & Explanation

. Popliteal artery, Popliteal vein, Tibial nerve

Explanation

Correct Answer: AThe case describes the anatomical relationship of these structures in the popliteal fossa: "The tibial nerve lies posterior to the popliteal vein which in turn is superficial to popliteal artery." This means the popliteal artery is the deepest structure, followed by the popliteal vein, and then the tibial nerve is the most superficial of these three structures.

Question 267

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty (TKA) on a 68-year-old female with a severe 25-degree valgus deformity, extensive lateral releases are required to balance the knee. Postoperatively, she exhibits a foot drop. Which of the following is the most likely cause of this complication?

. Direct transection of the tibial nerve
. Stretching of the common peroneal nerve
. Tourniquet-induced femoral nerve palsy
. Compression of the saphenous nerve
. Popliteal artery pseudoaneurysm compressing the sciatic nerve

Correct Answer & Explanation

. Stretching of the common peroneal nerve

Explanation

Common peroneal nerve palsy is a known complication following TKA in severe valgus knees. It is most often caused by traction or stretching of the nerve as the valgus deformity is acutely corrected.

Question 268

Topic: Total Knee Arthroplasty (TKA)

During a total knee arthroplasty (TKA), the surgeon checks the gap balancing. The knee is stable and symmetric in full extension, but tight in both medial and lateral compartments at 90 degrees of flexion. Which of the following adjustments is the most appropriate next step to correct this mismatch?

. Resect more distal femur
. Decrease the anterior-posterior (AP) size of the femoral component
. Increase the thickness of the tibial polyethylene insert
. Release the posterior cruciate ligament (PCL)
. Recut the proximal tibia with more posterior slope

Correct Answer & Explanation

. Decrease the anterior-posterior (AP) size of the femoral component

Explanation

A gap that is balanced in extension but tight in flexion indicates an overly tight flexion gap. The best way to increase the flexion gap without altering the extension gap is to downsize the femoral component (decreasing AP diameter) or translate it anteriorly.

Question 269

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon aims to achieve a balanced soft tissue envelope. What principle describes the ideal state where ligamentous tension is uniform throughout the range of motion?

. Arthrokinematics
. Kinematic alignment
. Mechanical axis alignment
. Ligament balancing
. Isometry

Correct Answer & Explanation

. Isometry

Explanation

Correct Answer: EIsometry, in the context of knee kinematics and ligamentous balance, refers to the property where the distance between the origins and insertions of the collateral ligaments remains relatively constant throughout the range of motion. Achieving this during total knee arthroplasty (via appropriate implant positioning and soft tissue releases) is crucial for ensuring uniform ligamentous tension, which contributes significantly to knee stability, kinematics, and overall function. Ligament balancing is the technique used to achieve this.

Question 270

Topic: 3. Adult Reconstruction (Hip & Knee)

An examiner asks you to 'talk me through a total hip arthroplasty.' Which aspect of your answer should you prioritize to demonstrate a comprehensive understanding, beyond just the technical steps?

. Detailing every instrument used in sequence.
. Focusing exclusively on the biomechanics of implant choice.
. Beginning with patient selection, indications, contraindications, pre-operative planning, intra-operative steps, potential complications and their management, and post-operative rehabilitation.
. Primarily discussing the historical evolution of hip arthroplasty techniques.
. Comparing various surgical approaches (e.g., anterior, posterior, lateral) without a broader context.

Correct Answer & Explanation

. Beginning with patient selection, indications, contraindications, pre-operative planning, intra-operative steps, potential complications and their management, and post-operative rehabilitation.

Explanation

Correct Answer: CWhile technical steps, biomechanics, and approaches are important, a comprehensive understanding of a procedure in an oral exam extends to the entire patient journey. Prioritizing patient selection, indications, contraindications, pre-operative planning, and post-operative care, alongside intra-operative details and complication management, demonstrates a holistic clinical perspective expected of a board-certified orthopedic surgeon. This shows an understanding of the 'why' and 'what next', not just the 'how'.

Question 271

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female experiences her third posterior dislocation following a primary total hip arthroplasty performed via a posterior approach. Radiographs demonstrate the acetabular component is placed in 5 degrees of retroversion and 45 degrees of abduction. The femoral component is well-fixed with 15 degrees of anteversion. What is the most appropriate definitive management?

. Prescribe a hip abduction brace for 12 weeks
. Revision of the femoral component to increase anteversion
. Revision of the acetabular component to 15-20 degrees of anteversion
. Placement of a constrained acetabular liner
. Conversion to a bipolar hemiarthroplasty

Correct Answer & Explanation

. Revision of the acetabular component to 15-20 degrees of anteversion

Explanation

The acetabular component is retroverted, which is the primary driver of this patient's recurrent posterior dislocations. Revision of the acetabular shell to correct the version (target 15-20 degrees of anteversion) is the definitive mechanical solution.

Question 272

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with a draining sinus tract over her right knee 6 weeks after a primary total knee arthroplasty. Cultures from a recent aspiration grew Methicillin-resistant Staphylococcus aureus (MRSA). According to current standards for periprosthetic joint infection (PJI), what is the most appropriate surgical treatment?

. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. One-stage revision arthroplasty
. Two-stage exchange arthroplasty with an antibiotic spacer
. Long-term suppressive intravenous antibiotics without surgery
. Above-knee amputation

Correct Answer & Explanation

. Two-stage exchange arthroplasty with an antibiotic spacer

Explanation

The presence of a draining sinus tract represents a chronic periprosthetic joint infection, which is a contraindication for DAIR. A two-stage exchange arthroplasty is the gold standard treatment for chronic PJI, especially with virulent organisms like MRSA.

Question 273

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient experiences recurrent posterior dislocations following a total hip arthroplasty. Radiographic evaluation demonstrates an acetabular cup abduction angle of 40 degrees and anteversion of 0 degrees. What is the primary cause of the instability?

. Excessive acetabular abduction
. Inadequate acetabular abduction
. Excessive acetabular anteversion
. Inadequate acetabular anteversion
. Femoral component retroversion

Correct Answer & Explanation

. Inadequate acetabular anteversion

Explanation

The "safe zone" for acetabular component placement generally dictates an anteversion of 15 +/- 10 degrees. An anteversion of 0 degrees represents a lack of anteversion (retroversion), which strongly predisposes the patient to posterior hip dislocation.

Question 274

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient is 8 weeks post-operative from a primary total knee arthroplasty. Despite diligent physical therapy and good pain control, their active range of motion is 15 degrees of extension to 65 degrees of flexion. Radiographs show appropriately sized and positioned components without loosening. What is the most appropriate next step in management?

. Continue current physical therapy for another 3 months before intervening
. Arthroscopic lysis of adhesions
. Manipulation under anesthesia (MUA)
. Open lysis of adhesions and polyethylene exchange
. Revision to a constrained condylar knee (CCK) arthroplasty

Correct Answer & Explanation

. Manipulation under anesthesia (MUA)

Explanation

For post-operative stiffness following TKA that fails to progress with physical therapy by 6-12 weeks, manipulation under anesthesia (MUA) is the most effective next step to break arthrofibrotic scar tissue before it fully matures.

Question 275

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with recurrent posterior instability following a primary total hip arthroplasty. Radiographs demonstrate well-fixed components, with the acetabular cup at 45 degrees of inclination and 20 degrees of anteversion. The femoral head is 32mm. Examination reveals severely atrophied abductor musculature. What is the most appropriate surgical management?

. Revision to a 36mm femoral head
. Revision of the acetabular component to increase anteversion
. Conversion to a dual mobility construct
. Application of a hip spica cast for 6 weeks
. Trochanteric advancement osteotomy

Correct Answer & Explanation

. Conversion to a dual mobility construct

Explanation

In cases of recurrent posterior instability with well-positioned, well-fixed components and deficient abductor musculature, a dual mobility construct provides increased jump distance and stability without altering cup position.

Question 276

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male is 4 weeks post-operative from a total knee arthroplasty. He presents with acute onset knee pain, swelling, and erythema for 2 days. Aspiration yields 65,000 WBCs with 95% PMNs. Radiographs show well-fixed components. What is the best management?

. Suppressive oral antibiotics
. One-stage revision arthroplasty
. Two-stage revision arthroplasty
. Arthroscopic lavage
. Open debridement, polyethylene exchange, and IV antibiotics

Correct Answer & Explanation

. Open debridement, polyethylene exchange, and IV antibiotics

Explanation

For an acute periprosthetic joint infection (symptoms lasting less than 3 weeks or occurring less than 4 weeks post-op) with well-fixed components, debridement, antibiotics, and implant retention (DAIR) with polyethylene liner exchange is the standard of care.

Question 277

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male with a history of a metal-on-metal THA 10 years ago presents with groin pain and a palpable mass. Serum cobalt and chromium levels are highly elevated. MRI demonstrates a large pseudotumor. What is the next best step?

. Corticosteroid injection into the pseudotumor
. Oral administration of metal chelating agents
. Observation and repeat MRI in 1 year
. Revision to a non-metal-on-metal bearing surface
. Aspiration of the mass for culture and sensitivity

Correct Answer & Explanation

. Revision to a non-metal-on-metal bearing surface

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors associated with elevated metal ions in metal-on-metal THA indicate progressive soft tissue destruction, requiring revision to a non-MoM bearing surface.

Question 278

Topic: 3. Adult Reconstruction (Hip & Knee)
A 32-year-old male sustains a Pauwels type III femoral neck fracture. He undergoes closed reduction and percutaneous pinning with three cannulated screws. At 6-month follow-up, radiographs show varus collapse and 1.5 cm of shortening, but no evidence of avascular necrosis on MRI. He reports moderate groin pain with weight-bearing. What is the most appropriate next step in management?
. Valgus intertrochanteric osteotomy
. Total hip arthroplasty
. Hemiarthroplasty
. Revision open reduction and internal fixation with a dynamic hip screw
. Non-vascularized fibular strut graft

Correct Answer & Explanation

. Valgus intertrochanteric osteotomy

Explanation

Valgus intertrochanteric osteotomy alters the mechanical axis, converting shear forces to compressive forces at the fracture site. It is the treatment of choice for young patients with femoral neck nonunion or varus collapse who have preserved femoral head viability.

Question 279

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with persistent left knee pain, swelling, and a draining sinus tract that developed two months ago, three years following a primary total knee arthroplasty (TKA). Aspiration yields 65,000 WBCs/mcL (92% PMNs), and cultures grow methicillin-resistant Staphylococcus aureus (MRSA). Radiographs show well-fixed components. What is the most appropriate surgical management?

. One-stage revision TKA
. Two-stage revision TKA with an antibiotic spacer
. Irrigation and debridement with polyethylene exchange
. Long-term suppressive intravenous antibiotics
. Knee arthrodesis

Correct Answer & Explanation

. Two-stage revision TKA with an antibiotic spacer

Explanation

For a chronic periprosthetic joint infection (symptoms > 4 weeks or presence of a sinus tract), especially with highly virulent organisms like MRSA, a two-stage revision TKA is the gold standard in the United States. Irrigation and debridement with liner exchange is reserved for acute infections (< 3 weeks) with susceptible organisms.

Question 280

Topic: 3. Adult Reconstruction (Hip & Knee)

During an ABOS oral examination, an examiner asks the candidate about the biomaterial science behind bearing surfaces in total hip arthroplasty. Which of the following factors most significantly contributes to the phenomenon of "stripe wear" in ceramic-on-ceramic articulations?

. Impingement of the femoral neck on the acetabular rim
. Microseparation of the head from the liner during the swing phase of gait
. Excessive anteversion of the acetabular component
. Use of a larger diameter femoral head
. Oxidation of the ceramic material over time

Correct Answer & Explanation

. Microseparation of the head from the liner during the swing phase of gait

Explanation

Stripe wear in ceramic-on-ceramic bearings is primarily caused by microseparation of the femoral head from the acetabular liner during the swing phase, followed by edge loading upon heel strike. This repetitive edge loading results in a characteristic linear wear track on the ceramic head.

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