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Total Hip Arthroplasty (THA) MCQs

Practice Set 1 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 1

Topic: Total Hip Arthroplasty (THA)

A 25-year-old athlete sustains an acute traumatic knee dislocation. In the emergency department, the Ankle-Brachial Index (ABI) is measured at 0.8. A CTA confirms a popliteal artery intimal tear. The vascular surgeon repairs the artery via a posterior approach. What is the most appropriate next orthopedic step?

. Immediate multiligament anatomical reconstruction
. Application of a spanning external fixator
. Application of a hinged knee brace locked in 30 degrees of flexion
. Cylinder cast application and early weight-bearing
. Delayed primary repair of the cruciate ligaments only

Correct Answer & Explanation

. Application of a spanning external fixator

Explanation

Following a vascular repair in the setting of a knee dislocation, a spanning external fixator is recommended to provide absolute skeletal stability and protect the delicate vascular anastomosis.

Question 2

Topic: Total Hip Arthroplasty (THA)

Which of the following statements regarding the treatment of thoracic disk herniations is true:

. The majority of patients can be treated nonoperatively.
. Surgical decompression is necessary in most cases.
. Laminectomy is the surgical procedure of choice.
. The anterior transthoracic approach is used for T1-T4 lesions.
. C ostotransversectomy is used for large central calcified herniations.

Correct Answer & Explanation

. The majority of patients can be treated nonoperatively.

Explanation

The majority (75%) of patients with thoracic disk herniations may be managed nonoperatively. Surgical procedures must adequately decompress the involved nerve root. Posterior approach by laminectomy is usually not adequate, and costotransversectomy is not effective for large central calcified herniations (an anterior approach is preferred). The anterior transthoracic approach is effective for T5-T12 lateral and anterior disk herniations.

Question 3

Topic: Total Hip Arthroplasty (THA)
A 48-year-old man presents with a closed head injury requiring intubation and isolated bilateral facet dislocation. The next appropriate step is:
. Closed reduction with axial traction with Gardner-Wells tongs
. Posterior open reduction and posterior cervical plating
. Emergent magnetic resonance imaging
. Neurostabilization until the patient's neurologic status improves
. Administration of Decadron (Merck & Co., West Point, Pa.) 10 mg/hr intravenously

Correct Answer & Explanation

. Emergent magnetic resonance imaging

Explanation

The patient has a severe closed head injury and is unable to tolerate close reduction maneuvers with Gardner-Wells tongs. Emergent magnetic resonance imaging should be obtained to evaluate the potential presence of a disk herniation at the dislocation. Should a disk herniation be present, anterior approach and diskectomy should be performed prior to reduction maneuvers.

Question 4

Topic: Total Hip Arthroplasty (THA)

A 10-year-old girl is predicted to have a 3.5 cm leg length discrepancy at skeletal maturity, with the right leg being shorter. She and her parents desire a minimal surgical intervention. What is the most appropriate management?

. Right femoral lengthening using a circular frame
. Left proximal tibial hemiepiphysiodesis
. Left femoral and tibial epiphysiodesis
. Shoe lift only
. Right proximal femoral osteotomy

Correct Answer & Explanation

. Left femoral and tibial epiphysiodesis

Explanation

For a predicted leg length discrepancy of 2-5 cm at maturity, an epiphysiodesis of the longer limb is the standard and least invasive surgical treatment. Discrepancies >5 cm generally require lengthening procedures.

Question 5

Topic: Total Hip Arthroplasty (THA)

A 5-year-old girl presents with an enlarged left lower extremity, varicose veins, and a port-wine stain extending from her thigh to her foot. No significant arteriovenous fistulas are noted. Which of the following is the most appropriate initial management for her projected 4 cm leg length discrepancy?

. Epiphysiodesis of the contralateral (unaffected) limb
. Epiphysiodesis of the affected limb
. Femoral lengthening of the affected limb using an external fixator
. Amputation of the affected limb
. Vascular bypass surgery

Correct Answer & Explanation

. Epiphysiodesis of the affected limb

Explanation

Klippel-Trenaunay syndrome involves capillary malformations, venous varicosities, and limb hypertrophy without high-flow AV fistulas. Management of the resulting limb length discrepancy typically involves appropriately timed epiphysiodesis of the hypertrophied (affected) limb.

Question 6

Topic: Total Hip Arthroplasty (THA)

A 4-year-old child presents with an enlarged left lower extremity, cutaneous port-wine stains, and prominent varicose veins. There is a 3 cm leg length discrepancy (left longer than right). What is the most appropriate initial management for the limb length inequality?

. Immediate tibial lengthening of the contralateral side
. Immediate femoral shortening of the affected side
. Prophylactic epiphysiodesis of the unaffected limb
. Shoe lift on the short side and observation
. Sclerotherapy of the vascular malformations to halt growth

Correct Answer & Explanation

. Shoe lift on the short side and observation

Explanation

Klippel-Trenaunay syndrome involves overgrowth of the affected limb. Initial management of the limb length discrepancy is conservative with a shoe lift and observation until skeletal maturity approaches or the discrepancy warrants epiphysiodesis.

Question 7

Topic: Total Hip Arthroplasty (THA)

Which part of the body is removed last in a posterior vertebral column resected via a posterior approach:

. The lamina
. The pedicles
. The anterior wall of the vertebral body
. The posterior vertebral cortex
. The transverse process

Correct Answer & Explanation

. The posterior vertebral cortex

Explanation

To protect and stabilize the neural elements, the posterior vertebral cortex is left intact to be resected last.

Question 8

Topic: Total Hip Arthroplasty (THA)

A 10-year-old girl is projected to have a 3.5 cm leg length discrepancy at skeletal maturity due to a prior distal femoral physeal arrest. Her current bone age matches her chronological age. Which of the following is the most appropriate surgical management?

. Contralateral proximal tibial epiphysiodesis
. Ipsilateral femoral lengthening
. Contralateral distal femoral epiphysiodesis
. Shoe lift only
. Ipsilateral distal femoral osteotomy

Correct Answer & Explanation

. Contralateral distal femoral epiphysiodesis

Explanation

For projected discrepancies between 2 and 5 cm, contralateral epiphysiodesis is the standard of care. Because the discrepancy originates in the femur, performing a distal femoral epiphysiodesis on the longer leg is the most appropriate choice.

Question 9

Topic: Total Hip Arthroplasty (THA)

A 65-year-old woman undergoes a total hip arthroplasty (THA) via a posterior approach. Postoperatively, she suffers recurrent posterior dislocations. Radiographs reveal the acetabular cup is placed in 30 degrees of inclination and 5 degrees of retroversion. Which surgical adjustment is most appropriate to stabilize the joint?

. Increase anteversion of the acetabular cup
. Increase retroversion of the acetabular cup
. Increase inclination of the acetabular cup
. Decrease anteversion of the acetabular cup
. Change to a smaller femoral head

Correct Answer & Explanation

. Increase anteversion of the acetabular cup

Explanation

A cup placed in retroversion predisposes the patient to posterior instability following a THA. The most appropriate surgical adjustment is to revise the component to increase its anteversion, targeting the Lewinnek safe zone of 15 (+/- 10) degrees.

Question 10

Topic: Total Hip Arthroplasty (THA)

A 68-year-old woman presents with her third posterior dislocation of a total hip arthroplasty (THA) performed 6 weeks ago via a posterior approach. Radiographs demonstrate well-fixed components with the acetabular cup in 45 degrees of abduction and 0 degrees of anteversion. What is the most likely primary cause of her recurrent instability?

. Abductor mechanism deficiency
. Inadequate acetabular component anteversion
. Excessive femoral offset
. Inadequate acetabular component abduction
. Polyethylene liner wear

Correct Answer & Explanation

. Inadequate acetabular component anteversion

Explanation

The patient's recurrent posterior dislocations are primarily due to inadequate acetabular anteversion (0 degrees). The safe zone for acetabular component placement is generally considered to be 15 +/- 10 degrees of anteversion and 40 +/- 10 degrees of abduction.

Question 11

Topic: Total Hip Arthroplasty (THA)

A 65-year-old female undergoes a right total hip arthroplasty via a posterior approach. On postoperative day 1, she exhibits a profound right foot drop and inability to dorsiflex her great toe. A compressive hematoma has been ruled out by urgent MRI. What is the most appropriate management?

. Immediate surgical exploration of the sciatic nerve
. Prescription of an ankle-foot orthosis (AFO) and observation
. Revision surgery to shorten the femoral offset
. Immediate administration of high-dose intravenous corticosteroids
. Lumbar epidural steroid injection

Correct Answer & Explanation

. Prescription of an ankle-foot orthosis (AFO) and observation

Explanation

Sciatic nerve palsy (specifically the peroneal division) is a known complication of THA. In the absence of a compressive hematoma or obvious intraoperative transection, the management is observation and an AFO to prevent equinus contracture while awaiting recovery.

Question 12

Topic: Total Hip Arthroplasty (THA)

A 70-year-old woman presents with recurrent posterior dislocations following a primary total hip arthroplasty performed via a posterior approach. Radiographic evaluation demonstrates an acetabular component in 5 degrees of retroversion and 45 degrees of abduction. The femoral stem is stable and placed in 15 degrees of anteversion. What is the most definitive surgical management?

. Revision of the femoral stem to increase its anteversion
. Revision of the acetabular component to increase anteversion
. Placement of a constrained acetabular liner without removing the shell
. Soft tissue repair of the posterior capsule and external rotators
. Conversion to a bipolar hemiarthroplasty

Correct Answer & Explanation

. Revision of the acetabular component to increase anteversion

Explanation

The normal target for acetabular component positioning is 15-20 degrees of anteversion and 40-45 degrees of abduction. Revising the malpositioned, retroverted acetabular shell to achieve proper anteversion addresses the primary biomechanical cause of her posterior instability.

Question 13

Topic: Total Hip Arthroplasty (THA)

A 68-year-old female undergoes a primary total hip arthroplasty (THA) via a posterior approach for severe osteoarthritis. Six weeks postoperatively, she sustains a posterior dislocation of the THA while bending forward to tie her shoes. Recurrent posterior dislocations are most strongly associated with which of the following technical component malpositioning errors?

. Excessive anteversion of the acetabular cup
. Retroversion of the acetabular cup or femoral stem
. Excessive lateral offset of the femoral stem
. Valgus positioning of the acetabular cup beyond 55 degrees
. Excessive intentional leg lengthening

Correct Answer & Explanation

. Retroversion of the acetabular cup or femoral stem

Explanation

Acetabular cup retroversion or insufficient femoral anteversion severely limits impingement-free internal rotation and flexion. This technical error predisposes a total hip arthroplasty to posterior dislocation when the hip is flexed, adducted, and internally rotated.

Question 14

Topic: Total Hip Arthroplasty (THA)

Correction of the congenital gibbus in spina bifida must follow which of these surgical principles:

. Long instrumentation
. Short instrumentation
. Avoidance of instrumentation
. Avoidance of bony resection
. Anterior approach to deformity

Correct Answer & Explanation

. Long instrumentation

Explanation

The leverage provided by long instrumentation prevents loss of correction and junctional deformity. Short instrumentation poses a risk of junctional kyphosis or loss of fixation. Because of the severe angular deformity, fusion in situ without correction will be followed by increasing deformity. Resection of one to three of the vertebrae on the lower limb of the kyphosis is essential to allow safe correction without excessive tension on vessels and viscera. The anterior approach to the gibbus is deep and impractical. This approach does not allow mechanically efficient instrumentation.

Question 15

Topic: Total Hip Arthroplasty (THA)

A 6-year-old boy has an enlarged right lower extremity compared to the left. Examination reveals a lateral port-wine stain and extensive superficial varicose veins. If his projected leg length discrepancy at skeletal maturity is 3 cm, what is the most appropriate initial orthopedic management?

. Immediate femoral shortening
. Contralateral epiphysiodesis timed appropriately before skeletal maturity
. Amputation and prosthetic fitting
. Ipsilateral femoral lengthening using an Ilizarov frame
. Observation with elastic compression stockings only

Correct Answer & Explanation

. Contralateral epiphysiodesis timed appropriately before skeletal maturity

Explanation

This patient has Klippel-Trenaunay syndrome, characterized by the triad of a capillary malformation (port-wine stain), venous malformations, and soft tissue/bony hypertrophy. A predicted limb length discrepancy of 2 to 5 cm at maturity is best treated with a timed contralateral epiphysiodesis.

Question 16

Topic: Total Hip Arthroplasty (THA)

A 1-year-old girl presents with a right lower extremity abnormality. Her parents report that she has been attempting to stand, but she has not yet walked. C linically, she has a stiff, flexed, varus right knee with an obvious leg length discrepancy. Her ankle is also in a varus position. She does not spontaneously flex or extend the knee from its flexed position. Radiographs show that she has complete tibial hemimelia. The best choice of treatment at this time for the condition is:

. Observation
. Syme amputation
. Limb lengthening
. Knee disarticulation
. Brown procedure

Correct Answer & Explanation

. Knee disarticulation

Explanation

Knee disarticulation eliminates the malformed knee and ankle, allows the use of a prosthesis at an early age to promote ambulation development, and has good long-term results. Observation is a poor option due to the severity of the deformity and the need for treatment to develop ambulation. Syme's amputation does not address the deformity of the knee. In general, joint malformation or instability precludes lengthening procedures. The Brown procedure centralizes the fibula at the knee and includes a Syme's amputation for the abnormal ankle. However, a functioning quadriceps is a prerequisite and there is a high likelihood of flexion contracture postoperatively.

Question 17

Topic: Total Hip Arthroplasty (THA)

Which of the following factors most significantly increases the risk of "squeaking" in a ceramic-on-ceramic total hip arthroplasty?

. A 28-mm femoral head
. Excessive acetabular cup anteversion
. Excessive femoral stem retroversion
. Use of a cemented femoral stem
. High body mass index

Correct Answer & Explanation

. Excessive acetabular cup anteversion

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which often results from a malpositioned acetabular component. Excessive cup anteversion or inclination disrupts the fluid film lubrication, leading to stripe wear and subsequent squeaking.

Question 18

Topic: Total Hip Arthroplasty (THA)

A 65-year-old woman undergoes a primary total hip arthroplasty via a posterior approach. Six weeks postoperatively, she presents to the emergency department with a posterior dislocation that occurred while rising from a low toilet seat. Which of the following component positions is most likely responsible for this instability?

. Excessive acetabular anteversion
. Decreased femoral anteversion
. Increased acetabular abduction
. Increased femoral offset
. Excessive anterior pelvic tilt

Correct Answer & Explanation

. Decreased femoral anteversion

Explanation

Decreased femoral anteversion (or retroversion) of the femoral component strongly predisposes a THA to posterior dislocation, particularly during hip flexion and internal rotation. Excessive acetabular anteversion typically leads to anterior instability.

Question 19

Topic: Total Hip Arthroplasty (THA)
Based on the CT scan findings described in the case, the acetabular bone defect is classified as Paprosky Type IIIA. Which of the following best describes the key characteristics of a Paprosky Type IIIA acetabular defect?
. Intact acetabular rim with cavitary defects in the superior dome.
. Segmental bone loss involving less than 50% of the superior dome, with an intact medial wall.
. Extensive superior segmental and cavitary bone loss, with a deficient superior dome and often medial wall perforation.
. Complete loss of host bone stock, requiring a custom triflange component.
. Minor cavitary defects with an intact acetabular column and rim.

Correct Answer & Explanation

. Extensive superior segmental and cavitary bone loss, with a deficient superior dome and often medial wall perforation.

Explanation

The case explicitly states the CT scan confirmed a Paprosky Type IIIA defect, characterized by 'extensive superior segmental and cavitary bone loss, with a deficient superior dome and medial wall perforation.' This classification indicates significant loss of more than 50% of host bone stock in the superior region, making primary cup fixation challenging. Option A describes a less severe defect, often Paprosky Type IIA or IIB. Option B is incorrect as Type IIIA involves significant segmental loss, typically more than 50%. Option D describes a Paprosky Type IV defect, which is more severe than IIIA, involving complete loss of host bone. Option E describes a Paprosky Type I defect, which is the least severe. Therefore, extensive superior segmental and cavitary bone loss with a deficient superior dome and often medial wall perforation accurately defines a Paprosky Type IIIA defect as described in the case.

Question 20

Topic: Total Hip Arthroplasty (THA)

The CT scan also confirmed a Paprosky Type IIB femoral bone defect. Considering this classification, what is the most appropriate surgical strategy for femoral reconstruction in this patient?

. A short, proximally coated cementless stem for metaphyseal fixation.
. A cemented femoral stem with extensive cancellous allografting.
. A long, modular, uncemented femoral stem designed for diaphyseal fixation, bypassing proximal bone loss.
. A custom-made femoral component with a proximal femoral replacement.
. Non-operative management with activity modification and analgesics.

Correct Answer & Explanation

. A long, modular, uncemented femoral stem designed for diaphyseal fixation, bypassing proximal bone loss.

Explanation

Correct Answer: CA Paprosky Type IIB femoral defect is characterized by proximal femoral bone loss with a widened femoral canal and a deficient metaphysis, but with an intact distal diaphysis capable of providing stable fixation. The case specifically states that templating favored 'a long, proximally coated, distally fixing modular revision stem' to 'bypass the proximal bone loss and achieve diaphyseal fixation.' Option A (short, proximally coated stem) is suitable for Paprosky Type I or IIA defects where the metaphysis is largely intact. Option B (cemented stem) is generally avoided in revision THA with significant bone loss due to concerns about cement mantle integrity and long-term fixation, especially when the canal is widened. Option D (proximal femoral replacement) is reserved for more severe defects (Paprosky Type IV) or tumor resections. Option E (non-operative management) is inappropriate given the patient's debilitating pain and progressive mechanical failure. Therefore, a long, modular, uncemented femoral stem designed for diaphyseal fixation, bypassing the area of proximal bone loss, is the correct strategy.

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