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Total Hip Arthroplasty (THA) MCQs

Practice Set 14 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 261

Topic: Total Hip Arthroplasty (THA)

When revising a total hip arthroplasty to reduce the risk of postoperative dislocation, increasing the femoral head size (e.g., from 28 mm to 36 mm) primarily improves stability by increasing the impingement-free range of motion and increasing which of the following parameters?

. Volumetric wear rate
. Jump distance
. Medialization of the center of rotation
. Risk of trunnionosis
. Acetabular component version

Correct Answer & Explanation

. Jump distance

Explanation

A larger femoral head enhances THA stability via two main mechanisms: 1) Increasing the head-neck ratio, which improves the impingement-free range of motion, and 2) Increasing the 'jump distance,' which is the vertical distance the femoral head must travel out of the acetabular socket before it dislocates. While a larger head may increase volumetric wear, that is an adverse effect, not a mechanism of stability.

Question 262

Topic: Total Hip Arthroplasty (THA)

When comparing ceramic-on-ceramic (CoC) to metal-on-polyethylene (MoP) total hip arthroplasties, which of the following is an established advantage of the CoC articulation?

. Elimination of the risk of bearing fracture
. Increased resistance to third-body wear
. Complete absence of squeaking
. Higher tolerance for component malposition
. Lower rate of impingement at the extremes of motion

Correct Answer & Explanation

. Increased resistance to third-body wear

Explanation

Ceramic-on-ceramic bearings have very high scratch resistance and are highly resistant to third-body wear compared to MoP bearings. However, they carry a known risk of catastrophic component fracture, have a lower tolerance for malposition (which can lead to edge loading, stripe wear, and squeaking), and do not inherently lower the rate of mechanical impingement.

Question 263

Topic: Total Hip Arthroplasty (THA)

A 55-year-old active male underwent a ceramic-on-ceramic total hip arthroplasty 2 years ago. He complains of a new-onset squeaking noise from his hip during certain movements. Evaluation reveals proper component fixation. Which factor is most strongly associated with squeaking in ceramic-on-ceramic THA?

. Use of an un-cemented femoral stem
. Smaller femoral head diameter
. Stripe wear from edge loading due to component malposition
. High patient BMI
. Excessive femoral anteversion

Correct Answer & Explanation

. Stripe wear from edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic bearings is strongly correlated with edge loading, which leads to localized stripe wear, fluid film disruption, and vibration. This is typically related to component malposition, particularly acetabular cup anteversion or inclination outside the safe zone, or microseparation during swing phase.

Question 264

Topic: Total Hip Arthroplasty (THA)

A 68-year-old male undergoes a primary Total Hip Arthroplasty via a posterior approach. Postoperatively, he exhibits a complete foot drop and inability to extend his toes. Which specific neural structure is most commonly injured to produce this deficit during THA?

. Tibial division of the sciatic nerve
. Common peroneal division of the sciatic nerve
. Femoral nerve
. Deep peroneal nerve
. Superior gluteal nerve

Correct Answer & Explanation

. Common peroneal division of the sciatic nerve

Explanation

The common peroneal division of the sciatic nerve is the most frequently injured nerve during a THA (most commonly from stretch during leg lengthening or retractor placement). It is more susceptible than the tibial division because it is tethered at the fibular head, is positioned more laterally, and has less connective tissue support within the sciatic sheath.

Question 265

Topic: Total Hip Arthroplasty (THA)

A surgeon is templating for a primary Total Hip Arthroplasty (THA) and wishes to maximize the primary arc of motion to delay mechanical impingement of the components, thereby reducing dislocation risk. Which of the following geometric modifications to the implant will most effectively achieve this goal?

. Maximizing the head-to-neck ratio
. Minimizing the head-to-neck ratio
. Increasing the femoral neck diameter
. Using a skirted modular femoral head
. Decreasing the lateral femoral offset

Correct Answer & Explanation

. Maximizing the head-to-neck ratio

Explanation

The impingement-free primary arc of motion in a THA is mathematically driven by the head-to-neck ratio. Maximizing this ratio (by using a larger diameter femoral head and a smaller diameter femoral neck) allows for greater excursion of the neck before it contacts the acetabular rim. Skirted heads and thicker necks decrease this ratio, causing earlier impingement and increasing dislocation risk.

Question 266

Topic: Total Hip Arthroplasty (THA)

A 60-year-old male undergoes a total hip arthroplasty using a ceramic-on-ceramic bearing. Two years postoperatively, he complains of an audible squeaking sound from the hip during walking, but denies pain. Which of the following factors is most strongly mechanically associated with squeaking in ceramic-on-ceramic THA?

. Acetabular component retroversion
. Use of a smaller diameter femoral head
. Impingement and edge loading
. Increased femoral stem offset
. Use of a highly cross-linked polyethylene liner

Correct Answer & Explanation

. Impingement and edge loading

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is multifactorial but is highly associated with edge loading due to component malposition, specifically acetabular cup malposition (steep cup inclination, excessive anteversion, or retroversion). This leads to impingement, micro-separation, and stripe wear, generating the characteristic squeaking sound.

Question 267

Topic: Total Hip Arthroplasty (THA)

A 55-year-old man who underwent a ceramic-on-ceramic total hip arthroplasty 3 years ago complains of a loud squeaking noise from his hip with bending and walking. Radiographs are unremarkable. Which of the following component positions is most strongly associated with this phenomenon?

. Acetabular component inclination of 35 degrees
. Acetabular component inclination of 55 degrees
. Femoral stem retroversion of 10 degrees
. Femoral stem anteversion of 15 degrees
. Increased lateral femoral offset

Correct Answer & Explanation

. Acetabular component inclination of 55 degrees

Explanation

Squeaking in ceramic-on-ceramic (CoC) THA is strongly correlated with edge loading and subsequent stripe wear of the ceramic components. Edge loading is most frequently caused by malpositioning of the acetabular component, particularly cup inclination greater than 45-50 degrees, or excessive anteversion/retroversion. An inclination of 55 degrees significantly increases the risk of edge loading and squeaking.

Question 268

Topic: Total Hip Arthroplasty (THA)

A 65-year-old female presents with groin pain and swelling three years after undergoing a primary total hip arthroplasty utilizing a metal head on a highly cross-linked polyethylene liner with a titanium femoral stem. Metal ion analysis and MRI are suggestive of trunnionosis (mechanically assisted crevice corrosion). Which of the following serum metal ion profiles is most characteristic of this specific complication?

. Significantly elevated Titanium with normal Cobalt and Chromium
. Markedly elevated Chromium with normal Cobalt
. Elevated Cobalt disproportionately higher than Chromium
. Elevated Chromium disproportionately higher than Cobalt
. Elevated Vanadium and Aluminum with normal Cobalt and Chromium

Correct Answer & Explanation

. Elevated Cobalt disproportionately higher than Chromium

Explanation

Trunnionosis, or mechanically assisted crevice corrosion at the head-neck junction of a total hip arthroplasty, typically involves a cobalt-chromium (CoCr) head on a titanium (Ti) alloy stem. Corrosion at this modular junction leads to the preferential release of cobalt ions. Consequently, patients with trunnionosis characteristically present with an elevated serum cobalt-to-chromium ratio (Co > Cr), distinguishing it from wear at a metal-on-metal articular surface where Co and Cr are typically elevated more equally.

Question 269

Topic: Total Hip Arthroplasty (THA)

A 68-year-old female experiences recurrent anterior dislocations following a right total hip arthroplasty performed via a posterior approach. Radiographs show the acetabular component has 55 degrees of inclination and 35 degrees of anteversion. The femoral stem is in neutral version. Which of the following is the most appropriate definitive management?

. Prescribe an abduction brace for 6 weeks.
. Revise the femoral stem to a retroverted position.
. Revise the acetabular component to decrease anteversion.
. Perform a greater trochanteric advancement.
. Exchange the femoral head to a larger diameter and add a constrained liner without changing the shell.

Correct Answer & Explanation

. Revise the acetabular component to decrease anteversion.

Explanation

The acetabular component is excessively anteverted (35 degrees) and over-inclined (55 degrees). The normal target (Lewinnek safe zone) is typically 15-20 degrees of anteversion and 40-45 degrees of inclination. Excessive anteversion strongly predisposes to anterior dislocation. The appropriate definitive treatment is revision of the malpositioned acetabular component to restore appropriate anteversion and inclination.

Question 270

Topic: Total Hip Arthroplasty (THA)

A patient with a ceramic-on-ceramic total hip arthroplasty (THA) complains of a loud squeaking noise during gait. This phenomenon is strongly associated with 'edge loading' of the ceramic components. Which of the following acetabular component position errors most significantly increases the risk of edge loading?

. Decreased cup inclination and decreased cup anteversion
. Increased cup inclination and excessive cup anteversion
. Decreased cup inclination and increased femoral offset
. Increased femoral offset and decreased cup anteversion
. Decreased femoral offset and decreased cup inclination

Correct Answer & Explanation

. Increased cup inclination and excessive cup anteversion

Explanation

Edge loading in a ceramic-on-ceramic THA occurs when the femoral head contacts the rim of the acetabular liner rather than the articulating concavity, leading to stripe wear, loss of fluid film lubrication, and squeaking. The risk of edge loading is markedly increased with suboptimal cup positioning, specifically increased cup inclination (a steep cup) and excessive anteversion or retroversion.

Question 271

Topic: Total Hip Arthroplasty (THA)

A 68-year-old male presents with recurrent posterior dislocations following a primary total hip arthroplasty performed via a posterior approach 6 months ago. Plain radiographs and CT evaluation demonstrate a well-fixed, bone-ingrown acetabular component with 20 degrees of abduction and 5 degrees of retroversion. What is the most definitive and appropriate surgical intervention?

. Exchange the modular femoral head for a larger diameter with a standard liner
. Advance the greater trochanter to increase abductor tension
. Revise the acetabular component to achieve proper anteversion and abduction
. Apply a constrained acetabular liner without altering component position
. Increase the femoral offset using a higher offset femoral stem

Correct Answer & Explanation

. Revise the acetabular component to achieve proper anteversion and abduction

Explanation

The patient has a malpositioned acetabular component. Normal 'safe zone' parameters are typically 40-50 degrees of abduction and 15-20 degrees of anteversion. The cup is significantly retroverted (5 degrees) and under-abducted (20 degrees, making it horizontal). Retroversion is a classic cause of posterior instability in flexion and internal rotation. The definitive treatment for recurrent dislocation due to a severely malpositioned, though well-fixed, cup is revision of the component to correct the alignment.

Question 272

Topic: Total Hip Arthroplasty (THA)

A 55-year-old female undergoes a primary total hip arthroplasty using a ceramic-on-ceramic bearing. At 2-year follow-up, she complains of an audible squeaking noise from the hip during specific movements. Which of the following acetabular component positions is most strongly associated with the development of this complication?

. Acetabular inclination of 40 degrees and anteversion of 15 degrees
. Excessive acetabular anteversion and high inclination
. Acetabular inclination of 35 degrees and retroversion
. Excessive cup depth (medialization)
. Inferior cup placement

Correct Answer & Explanation

. Excessive acetabular anteversion and high inclination

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which typically occurs due to component malposition, specifically excessive acetabular inclination (vertical cup) and/or excessive anteversion. Edge loading leads to loss of fluid film lubrication and stripe wear on the femoral head.

Question 273

Topic: Total Hip Arthroplasty (THA)

In complex total hip arthroplasty, a dual mobility articulation may be utilized to decrease the risk of dislocation. The primary biomechanical mechanism by which a dual mobility construct prevents instability is:

. Decreased volumetric wear compared to standard bearings
. Increased jump distance
. Elimination of backside wear
. Increased lateral offset without modularity
. Prevention of trunnionosis

Correct Answer & Explanation

. Increased jump distance

Explanation

A dual mobility construct consists of a small femoral head captive within a larger polyethylene liner, which itself articulates freely within a highly polished metallic acetabular shell. This effectively increases the effective head size (the large poly liner acts as the head during extreme range of motion), thereby massively increasing the 'jump distance' required for the construct to dislocate.

Question 274

Topic: Total Hip Arthroplasty (THA)

A 65-year-old man undergoes primary THA with a ceramic-on-ceramic bearing. At 2-year follow-up, he complains of a reproducible squeaking noise when walking. Which of the following factors is most strongly associated with squeaking in ceramic-on-ceramic total hip arthroplasty?

. Femoral offset less than 35mm
. Cup anteversion of 15 degrees
. Edge loading due to component malposition
. Use of a 28mm femoral head
. Body mass index less than 25

Correct Answer & Explanation

. Edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which typically occurs due to acetabular component malposition (such as steep inclination or improper anteversion). This leads to microseparation and stripe wear, producing the characteristic squeak.

Question 275

Topic: Total Hip Arthroplasty (THA)

A 40-year-old woman sustains a coronal shear fracture of the capitellum extending medially to involve the majority of the trochlea. According to the Dubberley classification, what type of fracture is this, and what is the preferred surgical approach?

. Type 1A, lateral approach
. Type 2A, medial approach
. Type 3B, universal posterior approach with olecranon osteotomy
. Type 1B, anterior approach
. Type 3A, extended lateral approach

Correct Answer & Explanation

. Type 3B, universal posterior approach with olecranon osteotomy

Explanation

A coronal shear fracture involving the capitellum and the trochlea is a Dubberley Type 3. Due to the extensive medial involvement, a universal posterior approach, often combined with an olecranon osteotomy, is required for adequate visualization and fixation.

Question 276

Topic: Total Hip Arthroplasty (THA)

A patient with a modular uncemented total hip arthroplasty presents with unexplained hip pain and rising serum cobalt levels. Radiographs show no loosening. Fretting and mechanically assisted crevice corrosion are most likely occurring at which of the following interfaces?

. Femoral head and polyethylene liner
. Modular taper junction of a femoral stem
. Bone-cement interface
. Cement-implant interface
. Ceramic-ceramic articulation

Correct Answer & Explanation

. Modular taper junction of a femoral stem

Explanation

Mechanically assisted crevice corrosion (MACC), often referred to as trunnionosis, occurs at the modular head-neck taper junction. Micromotion disrupts the passive oxide layer, leading to localized corrosion and release of metal ions.

Question 277

Topic: Total Hip Arthroplasty (THA)

A surgeon is performing a posterior (Moore) approach to the hip. The short external rotators are detached near their trochanteric insertions and reflected posteriorly. Which muscle is intentionally left intact to protect the medial circumflex femoral artery (MFCA) from iatrogenic injury?

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

Correct Answer & Explanation

. Obturator externus

Explanation

The main blood supply to the femoral head is the deep branch of the medial circumflex femoral artery (MFCA). It runs posterior to the obturator externus tendon, which should be preserved during the posterior approach to protect the vessel.

Question 278

Topic: Total Hip Arthroplasty (THA)

During an anterior approach to the ankle for arthrodesis, the surgeon develops the interval between the extensor hallucis longus (EHL) and the extensor digitorum longus (EDL). Which neurovascular bundle lies deep within this interval and must be mobilized and protected?

. Posterior tibial artery and tibial nerve
. Anterior tibial artery and superficial peroneal nerve
. Anterior tibial artery and deep peroneal nerve
. Peroneal artery and sural nerve
. Dorsalis pedis artery and saphenous nerve

Correct Answer & Explanation

. Anterior tibial artery and deep peroneal nerve

Explanation

The primary neurovascular structures at risk during the anterior approach to the ankle are the anterior tibial artery and the deep peroneal nerve. They are consistently found deep to the extensor retinaculum in the interval between the EHL and EDL.

Question 279

Topic: Total Hip Arthroplasty (THA)

During a posterior approach to the hip (Kocher-Langenbeck), the surgeon tags and releases the short external rotators. To preserve the primary blood supply to the adult femoral head, the surgeon must protect the ascending branch of the medial femoral circumflex artery. Where does this crucial vessel typically run?

. Between the piriformis and superior gemellus
. Anterior to the obturator externus
. Superior to the upper border of the quadratus femoris
. Through the substance of the gluteus medius
. Along the anterior border of the gluteus minimus

Correct Answer & Explanation

. Superior to the upper border of the quadratus femoris

Explanation

The ascending branch of the medial femoral circumflex artery (MFCA) typically courses anterior to the quadratus femoris and superior to its upper border. Staying at or above the superior border of the quadratus femoris during rotator release protects this critical blood supply.

Question 280

Topic: Total Hip Arthroplasty (THA)

During a posterior approach to the hip, protecting the primary blood supply to the femoral head is critical. The medial femoral circumflex artery (MFCA) courses deep to which of the following short external rotators?

. Superficial to the piriformis
. Superficial to the superior gemellus
. Deep to the quadratus femoris
. Inferior to the obturator externus
. Along the inferior border of the gluteus minimus

Correct Answer & Explanation

. Deep to the quadratus femoris

Explanation

The deep branch of the MFCA passes deep (anterior) to the quadratus femoris. To protect the blood supply to the femoral head during a posterior approach, the quadratus femoris should be released with a cuff or spared, and the obturator externus must remain intact.

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