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Total Hip Arthroplasty (THA) MCQs

Practice Set 25 of 36

This practice set contains high-yield board review questions covering key concepts in Total Hip Arthroplasty (THA). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 481

Topic: Total Hip Arthroplasty (THA)

A 72-year-old male presents with a periprosthetic femur fracture around a cemented femoral stem 10 years post-THA. Radiographs show a fracture extending from the lesser trochanter to the distal tip of the stem, with a radiographically loose stem and poor bone stock. What is the most appropriate management?

. Open reduction and internal fixation with a lateral locking plate
. Revision to a fully porous-coated cylindrical long stem
. Revision to a fluted, tapered modular stem
. Cortical strut allograft only
. Cable fixation alone

Correct Answer & Explanation

. Revision to a fluted, tapered modular stem

Explanation

This is a Vancouver B3 fracture, characterized by a fracture around a loose stem with poor bone stock. A fluted, tapered modular stem or proximal femoral replacement is indicated to bypass the defect and achieve diaphyseal fixation.

Question 482

Topic: Total Hip Arthroplasty (THA)

A 65-year-old patient with a ceramic-on-ceramic total hip arthroplasty (THA) presents with an audible squeak with walking. Which factor is most strongly associated with this phenomenon?

. Acetabular component retroversion
. Neck-shaft impingement
. Femoral stem subsidence
. Elevated body mass index
. Edge loading due to component malposition

Correct Answer & Explanation

. Edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, often due to acetabular cup malposition (such as excessive steepness or anteversion). This disrupts fluid film lubrication and causes stripe wear and subsequent squeaking.

Question 483

Topic: Total Hip Arthroplasty (THA)

A 66-year-old female presents with squeaking from her total hip arthroplasty placed 4 years ago. She has a ceramic-on-ceramic bearing. Which of the following factors is most strongly associated with the development of this complication?

. Use of a highly cross-linked polyethylene liner
. Low body mass index (BMI < 20)
. Edge loading due to high acetabular component inclination or version mismatch
. Impingement of the femoral neck on the posterior soft tissues
. Femoral component subsidence

Correct Answer & Explanation

. Edge loading due to high acetabular component inclination or version mismatch

Explanation

Squeaking in ceramic-on-ceramic THAs is heavily associated with edge loading, which disrupts the fluid lubrication film. Edge loading typically results from cup malposition, specifically high inclination or a mismatch in anteversion, leading to stripe wear on the ceramic head.

Question 484

Topic: Total Hip Arthroplasty (THA)

A surgeon utilizes a collarless, polished, double-tapered cemented femoral stem (e.g., Exeter design) for a primary THA. What is the fundamental biomechanical principle by which this specific stem design achieves long-term stability?

. Shape-closed design requiring intimate, non-yielding contact with the cement mantle
. Force-closed (taper-slip) design allowing controlled distal subsidence within the cement mantle to increase radial compressive forces
. Proximal off-loading through collar impaction on the medial calcar
. Direct osteointegration onto the polished surface
. Creation of sheer stresses at the cement-bone interface to stimulate hypertrophy

Correct Answer & Explanation

. Force-closed (taper-slip) design allowing controlled distal subsidence within the cement mantle to increase radial compressive forces

Explanation

Polished, collarless, tapered stems operate on a force-closed or 'taper-slip' principle. The polished surface lacks bonding, allowing the stem to predictably subside into the cement mantle, converting axial loads into compressive radial forces against the cement and bone.

Question 485

Topic: Total Hip Arthroplasty (THA)



A 42-year-old male with a history of severe traumatic brain injury requires a THA for post-traumatic hip osteoarthritis. Radiographs preoperatively demonstrate massive heterotopic ossification (Brooker Class IV) bridging the joint. Following resection and THA, what is the most appropriate prophylaxis to prevent recurrence?

. Oral bisphosphonates for 6 months
. Single-fraction localized external beam radiation therapy (700 cGy) postoperatively
. Intravenous corticosteroids for 48 hours postoperatively
. Continuous passive motion (CPM) machine for 4 weeks
. High-dose oral calcium channel blockers

Correct Answer & Explanation

. Single-fraction localized external beam radiation therapy (700 cGy) postoperatively

Explanation

Patients with prior severe heterotopic ossification, especially with neurogenic risk factors, are at very high risk for recurrence. Prophylaxis with single-dose localized radiation (given preop or within 72 hours postop) or oral NSAIDs (like Indomethacin) is the standard of care.

Question 486

Topic: Total Hip Arthroplasty (THA)

During a posterior approach for a TLIF at L4-L5, a pedicle screw is being placed into the right L4 vertebra. A medial breach of the pedicle wall occurs. Which neural structure is at greatest risk of iatrogenic injury?

. The exiting L3 nerve root
. The exiting L4 nerve root
. The traversing L4 nerve root
. The traversing L5 nerve root
. The sympathetic chain

Correct Answer & Explanation

. The traversing L5 nerve root

Explanation

A medial breach of the lumbar pedicle endangers the traversing nerve root of that same level (the L4 root at the L4 pedicle). An inferior pedicle breach, conversely, risks the exiting nerve root of that level (the L4 exiting root).

Question 487

Topic: Total Hip Arthroplasty (THA)

A 45-year-old highly active patient requires a total hip arthroplasty. A ceramic-on-ceramic bearing couple is selected. Compared to a traditional metal-on-polyethylene bearing, what is the primary tribological advantage of the ceramic-on-ceramic articulation?

. Elimination of the risk of catastrophic component fracture
. Lower resistance to third-body wear
. Lowest volumetric wear rate among bearing couples
. Increased tolerance to edge-loading and component malposition
. Generation of osteoinductive wear debris

Correct Answer & Explanation

. Lowest volumetric wear rate among bearing couples

Explanation

Ceramic-on-ceramic bearings exhibit the lowest volumetric wear rate due to their extreme hardness, high scratch resistance, and excellent fluid film lubrication. However, they are sensitive to malposition (edge-loading), squeaking, and have a risk of brittle fracture.

Question 488

Topic: Total Hip Arthroplasty (THA)

During a posterior approach to the hip, preserving the insertion of which of the following muscles protects the deep branch of the medial femoral circumflex artery (MFCA)?

. Piriformis
. Superior gemellus
. Obturator internus
. Obturator externus
. Quadratus femoris

Correct Answer & Explanation

. Obturator externus

Explanation

The deep branch of the MFCA courses posteriorly between the quadratus femoris and obturator externus. Maintaining the obturator externus tendon intact protects the artery from iatrogenic injury during a posterior approach.

Question 489

Topic: Total Hip Arthroplasty (THA)

A surgeon is performing a posterior approach to the popliteal fossa. Which of the following structures is located most deeply (closest to the joint capsule)?

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

Correct Answer & Explanation

. Popliteal artery

Explanation

From superficial to deep, the structures in the popliteal fossa are the tibial nerve, popliteal vein, and popliteal artery. The popliteal artery lies deepest, resting directly against the posterior aspect of the femur and knee joint capsule.

Question 490

Topic: Total Hip Arthroplasty (THA)

To avoid injury to the medial femoral circumflex artery (MFCA) during a posterior approach to the hip, an essential anatomical landmark is the superior border of which muscle?

. Piriformis
. Obturator internus
. Quadratus femoris
. Gluteus medius
. Superior gemellus

Correct Answer & Explanation

. Quadratus femoris

Explanation

The ascending branch of the MFCA courses posteriorly between the superior border of the quadratus femoris and the inferior gemellus. Preserving the superior portion of the quadratus femoris tendon during a posterior approach helps protect this critical blood supply to the femoral head.

Question 491

Topic: Total Hip Arthroplasty (THA)

A patient develops anterolateral thigh numbness following a direct anterior approach to the hip. The injured nerve typically exits the pelvis in which relation to the ASIS?

. Medial to the ASIS under the inguinal ligament
. Lateral to the ASIS over the iliac crest
. Through the deep inguinal ring
. Posterior to the anterior inferior iliac spine
. Piercing the sartorius muscle belly directly

Correct Answer & Explanation

. Medial to the ASIS under the inguinal ligament

Explanation

The lateral femoral cutaneous nerve typically exits the pelvis deep to the inguinal ligament, just medial to the anterior superior iliac spine (ASIS). Identifying and protecting this nerve is critical during the anterior approach to the hip.

Question 492

Topic: Total Hip Arthroplasty (THA)

A girl with a 3 cm right leg length discrepancy (LLD) has a skeletal bone age of 11 years. Assuming skeletal maturity at age 14, what is the most appropriate management to achieve limb equality at maturity based on the Menelaus method?

. Left distal femoral epiphysiodesis immediately
. Left proximal tibial epiphysiodesis immediately
. Right distal femoral lengthening immediately
. Left distal femoral and proximal tibial epiphysiodesis at age 13
. Right proximal tibial epiphysiodesis immediately

Correct Answer & Explanation

. Left distal femoral epiphysiodesis immediately

Explanation

The Menelaus method estimates distal femoral growth at 10 mm per year. With 3 years of growth remaining (bone age 11 to 14), a contralateral left distal femoral epiphysiodesis will yield approximately 3 cm of relative correction, matching her discrepancy.

Question 493

Topic: Total Hip Arthroplasty (THA)

An 8-year-old girl has a predicted leg length discrepancy of 3.5 cm at maturity due to a prior distal femoral physeal fracture. What is the most appropriate definitive management?

. Contralateral distal femoral epiphysiodesis at the appropriate age
. Ipsilateral femoral lengthening with an external fixator now
. Permanent shoe lift application
. Immediate contralateral proximal tibial epiphysiodesis
. Ipsilateral acute femoral shortening

Correct Answer & Explanation

. Contralateral distal femoral epiphysiodesis at the appropriate age

Explanation

A predicted leg length discrepancy of 2.0 to 5.0 cm at maturity is optimally treated with a precisely timed contralateral epiphysiodesis. Lengthening is generally reserved for discrepancies greater than 5 cm.

Question 494

Topic: Total Hip Arthroplasty (THA)

An 11-year-old girl with a skeletal age of 11 presents with a projected leg length discrepancy (LLD) of 3 cm. Assuming standard growth rates, how much length correction can be anticipated if a contralateral distal femoral epiphysiodesis is performed today?

. 10 mm
. 18 mm
. 30 mm
. 45 mm
. 60 mm

Correct Answer & Explanation

. 30 mm

Explanation

Girls typically reach skeletal maturity at age 14, leaving 3 years of growth. The distal femoral physis grows at approximately 10 mm (3/8 inch) per year, yielding 30 mm of correction over 3 years.

Question 495

Topic: Total Hip Arthroplasty (THA)

A patient presents with a projected leg length discrepancy at maturity of 1.5 cm due to a mild congenital hemihypertrophy. What is the most appropriate management recommendation?

. Contralateral distal femoral epiphysiodesis
. Ipsilateral femoral lengthening over a nail
. Observation or use of a shoe lift
. Ipsilateral proximal tibial lengthening
. Contralateral proximal tibial epiphysiodesis

Correct Answer & Explanation

. Observation or use of a shoe lift

Explanation

Projected leg length discrepancies of less than 2.0 cm at skeletal maturity are generally asymptomatic and do not require surgical intervention. They are best managed with observation or a simple shoe lift if symptomatic.

Question 496

Topic: Total Hip Arthroplasty (THA)

A 40-year-old patient presents with a symptomatic valgus deformity of 15 degrees originating entirely within the distal femur. To restore the mechanical axis while avoiding leg length discrepancy, which procedure is mechanically most sound if lengthening is strictly avoided?

. Lateral opening-wedge proximal tibial osteotomy
. Medial opening-wedge high tibial osteotomy
. Medial closing-wedge distal femoral osteotomy
. Focal dome osteotomy of the tibial diaphysis
. Proximal fibular excision and lateral closing-wedge tibial osteotomy

Correct Answer & Explanation

. Medial closing-wedge distal femoral osteotomy

Explanation

A femoral deformity should be corrected at the femur (avoiding compensatory deformities). A medial closing-wedge distal femoral osteotomy corrects valgus. While lateral opening-wedge is also an option, medial closing avoids lengthening and requires less grafting.

Question 497

Topic: Total Hip Arthroplasty (THA)



A patient with a 4 cm structural right leg length discrepancy stands barefoot. To maintain truncal balance and visual gaze, which compensatory mechanism is primarily utilized by the pelvis and hips?

. Right hip abduction and left hip adduction
. Left hip abduction and right hip adduction
. Bilateral knee flexion
. Equinus positioning of the left ankle
. Lumbar scoliosis convex to the left

Correct Answer & Explanation

. Left hip abduction and right hip adduction

Explanation

When standing with a short right leg, the pelvis drops on the right side. This effectively positions the right hip in relative adduction and the longer left leg in relative abduction to maintain balance.

Question 498

Topic: Total Hip Arthroplasty (THA)

A 65-year-old man undergoes a primary total hip arthroplasty. Intraoperatively, the surgeon utilizes a femoral stem that decreases the patient's native femoral offset by 10 mm while perfectly restoring the native leg length. Which of the following biomechanical consequences is most likely to occur as a direct result of this change?

. Decreased joint reactive force across the hip
. Increased abductor muscle force required during the stance phase of gait
. Increased impingement-free range of motion
. Increased tension on the iliotibial band
. Lateralization of the hip center of rotation

Correct Answer & Explanation

. Increased abductor muscle force required during the stance phase of gait

Explanation

Correct Answer: Increased abductor muscle force required during the stance phase of gaitFemoral offset is the perpendicular distance from the center of rotation of the femoral head to the anatomical axis of the femur. Decreasing the femoral offset shortens the abductor moment arm. Because the body weight moment arm remains constant, the abductor muscles must generate significantly more force to maintain a level pelvis during the single-leg stance phase of gait. This increased abductor force consequently increases the overall joint reactive force across the hip. Decreasing offset also increases the risk of bony or implant impingement, thereby decreasing impingement-free range of motion, and decreases tension on the iliotibial band and abductors, potentially leading to instability.

Question 499

Topic: Total Hip Arthroplasty (THA)

A 70-year-old woman undergoes a primary total hip arthroplasty via a posterior approach. Postoperatively, she suffers three recurrent posterior dislocations, all occurring when she attempts to stand up from a low chair. Radiographic evaluation reveals that the acetabular component is placed in 10 degrees of anteversion and 45 degrees of inclination. The femoral stem is in 15 degrees of anteversion. What is the most appropriate surgical intervention to address her instability?

. Revision of the acetabular component to increase anteversion
. Revision of the acetabular component to decrease anteversion
. Revision of the femoral component to decrease anteversion
. Application of a hip spica cast for 6 weeks
. Trochanteric advancement to increase abductor tension

Correct Answer & Explanation

. Revision of the acetabular component to increase anteversion

Explanation

Correct Answer: Revision of the acetabular component to increase anteversionThe patient is experiencing recurrent posterior dislocations due to component malposition. The Lewinnek safe zone for acetabular component placement is 15 +/- 10 degrees of anteversion (i.e., 5 to 25 degrees, though modern targets often aim for 20-25 degrees) and 40 +/- 10 degrees of inclination. However, combined anteversion (acetabular + femoral) is critical and should ideally be between 25 and 45 degrees. In this patient, the acetabular cup is in only 10 degrees of anteversion, which is relatively retroverted/under-anteverted, predisposing her to posterior instability during hip flexion (such as rising from a low chair). The femoral stem is in a normal range (15 degrees). The most appropriate treatment is revision of the acetabular component to increase its anteversion, thereby restoring proper combined anteversion and preventing posterior impingement and dislocation.

Question 500

Topic: Total Hip Arthroplasty (THA)

During a posterior approach to the hip for a total hip arthroplasty, the surgeon identifies the piriformis tendon and the short external rotators. These structures are tagged and released near their femoral insertions. To prevent significant postoperative hematoma, a specific arterial branch located near the inferior border of the obturator externus and superior border of the quadratus femoris must be identified and ligated. From which major artery does this branch originate?

. Lateral femoral circumflex artery
. Medial femoral circumflex artery
. Inferior gluteal artery
. Superior gluteal artery
. Obturator artery

Correct Answer & Explanation

. Medial femoral circumflex artery

Explanation

Correct Answer: Medial femoral circumflex arteryDuring the posterior approach to the hip (Moore or Southern approach), the short external rotators (piriformis, superior gemellus, obturator internus, inferior gemellus) are released from the greater trochanter. The ascending branch of the medial femoral circumflex artery (MFCA) is consistently found coursing vertically near the inferior border of the obturator externus and the superior border of the quadratus femoris. It is critical to identify, coagulate, or ligate this vessel during the deep dissection to prevent excessive intraoperative bleeding and postoperative hematoma formation. The MFCA is the primary blood supply to the adult femoral head, but in the setting of THA, the head is resected, so ligating this branch is standard practice.

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