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Total Hip Arthroplasty (THA) MCQs

Practice Set 9 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 161

Topic: Total Hip Arthroplasty (THA)

In the setting of recurrent instability after THA, a dual-mobility articulation is often utilized. Which of the following describes the primary tribological mechanism that increases stability in this design?

. The large inner metal head articulates primarily with the small polyethylene liner, preventing cam impingement
. The inner head is constrained within the polyethylene liner to prevent dissociation under distraction forces
. The large outer polyethylene liner articulates with the polished metal acetabular shell at the extremes of motion, increasing the effective head size and jump distance
. The polyethylene liner functions as a bipolar component that locks in full extension
. The skirted modular neck increases the impingement-free range of motion prior to subluxation

Correct Answer & Explanation

. The large outer polyethylene liner articulates with the polished metal acetabular shell at the extremes of motion, increasing the effective head size and jump distance

Explanation

Dual-mobility constructs feature two articulations: a smaller inner articulation (metal/ceramic head in polyethylene) for primary daily motion, and a larger outer articulation (polyethylene liner in a highly polished metal shell) that engages at extremes of motion. This larger outer diameter increases the "jump distance" required for the head to dislocate, significantly reducing the risk of instability.

Question 162

Topic: Total Hip Arthroplasty (THA)

A 78-year-old female presents for revision THA. Radiographs demonstrate a complete transverse separation of the superior and inferior hemi-pelves through the acetabulum. Which of the following surgical constructs is currently considered the most reliable method for achieving initial mechanical stability and long-term biologic fixation in this setting (chronic pelvic discontinuity)?

. Cemented all-polyethylene cup with an ilioischial plate
. Highly porous metal construct (e.g., cup-cage construct or custom triflange acetabular component)
. Impacted cancellous bone graft with a standard hemispherical titanium cup
. Anti-protrusio cage alone
. Bipolar hemiarthroplasty articulating on native acetabular bone

Correct Answer & Explanation

. Highly porous metal construct (e.g., cup-cage construct or custom triflange acetabular component)

Explanation

For chronic pelvic discontinuity, bridging the discontinuity with a construct that provides immediate rigid mechanical stability and allows for biologic ingrowth is the gold standard. Modern techniques heavily favor highly porous metal constructs, such as a cup-cage system, distraction techniques with jumbo tantalum cups, or custom triflange components.

Question 163

Topic: Total Hip Arthroplasty (THA)
Figure 8 shows the radiograph of a 72-year-old man who has had severe pain in the left hip for the past 3 weeks. History reveals alcohol abuse. The next most appropriate step should consist of:
. hip aspiration.
. Doppler ultrasound.
. AP tomograms.
. a CT scan.
. a technetium Tc 99m bone scan.

Correct Answer & Explanation

. hip aspiration.

Explanation

The radiograph reveals destruction of the femoral head with loss of the articular cartilage. These findings are consistent with an infected hip, and aspiration will confirm the diagnosis. Although the patient could have advanced osteonecrosis, typically the cartilage interval is maintained and such destruction is rarely associated with osteonecrosis.

Question 164

Topic: Total Hip Arthroplasty (THA)

A 45-year-old male who underwent a ceramic-on-ceramic total hip arthroplasty 4 years ago complains of a loud squeaking noise from his hip with every step. He denies pain or instability. Which of the following is the most significant risk factor for this phenomenon?

. High patient BMI
. Component malposition leading to edge loading
. The use of a small-diameter femoral head
. The presence of highly cross-linked polyethylene
. Use of a titanium alloy femoral stem

Correct Answer & Explanation

. High patient BMI

Explanation

Squeaking in ceramic-on-ceramic THA is heavily associated with stripe wear caused by edge loading. This most commonly results from component malposition, specifically excessive acetabular cup anteversion or inclination.

Question 165

Topic: Total Hip Arthroplasty (THA)

A 65-year-old female presents with recurrent anterior dislocations of her total hip arthroplasty. Intraoperative evaluation during revision reveals that the well-fixed acetabular component is in 35 degrees of anteversion, and the well-fixed femoral stem is in 20 degrees of anteversion. What is the most appropriate management?

. Revision of the femoral stem to a retroverted position
. Revision of the acetabular component to decrease anteversion
. Application of a constrained acetabular liner
. Advancement of the greater trochanter
. Conversion to a bipolar hemiarthroplasty

Correct Answer & Explanation

. Revision of the femoral stem to a retroverted position

Explanation

Combined anteversion in THA should ideally be between 25 and 45 degrees. With a combined anteversion of 55 degrees, the patient is highly prone to anterior dislocation, and revising the cup to decrease anteversion addresses the source of instability.

Question 166

Topic: Total Hip Arthroplasty (THA)

A patient complains that their operative leg feels longer after a primary THA. Clinical examination reveals the distance from the umbilicus to the medial malleolus is equal bilaterally, but the distance from the anterior superior iliac spine (ASIS) to the medial malleolus is 2 cm longer on the operative side. Which of the following best explains these findings?

. True leg length discrepancy
. Apparent leg length discrepancy due to pelvic obliquity
. Abductor muscle weakness
. Fixed adduction contracture of the hip
. Lumbar scoliosis

Correct Answer & Explanation

. True leg length discrepancy

Explanation

Measurements from the ASIS to the medial malleolus evaluate true leg length, while measurements from the umbilicus to the medial malleolus evaluate apparent leg length. A longer ASIS-malleolus distance confirms a true leg length discrepancy, with pelvic tilt masking the apparent length.

Question 167

Topic: Total Hip Arthroplasty (THA)
A 65-year-old active woman undergoes elective total hip replacement in which a posterior approach is used. She has minimal pain and is discharged to home 2 days after surgery. Four weeks later, she dislocates her hip while shaving her legs. She undergoes a closed reduction in the emergency department. Postreduction radiographs show a reduced hip with well-fixed components in satisfactory alignment. What is the most appropriate management of this condition from this point forward?
. Observation and patient education regarding hip dislocation precautions
. Revision to a larger-diameter femoral head
. Revision to a constrained acetabular component
. Application of a hip orthosis for 3 months

Correct Answer & Explanation

. Observation and patient education regarding hip dislocation precautions

Explanation

First-time early dislocations are often treated successfully without revision surgery, especially when no component malalignment is present. In this clinical scenario, it appears the patient would benefit from better education about dislocation precautions. Hip orthoses are of questionable benefit unless the patient is cognitively impaired. Revision surgery can be successful but is usually reserved for patients with recurrent dislocations.

Question 168

Topic: Total Hip Arthroplasty (THA)
A 70-year-old man undergoes removal of an infected total hip arthroplasty (THA) and insertion of an articulating antibiotic-loaded spacer to treat a deep periprosthetic hip infection. While in a nursing home receiving intravenous antibiotics 3 weeks after surgery, the patient trips and falls. Examination reveals swelling in the mid and distal thigh, intact skin and neurovascular structures, and severe pain with knee or hip movement. Radiographs of the femur are shown in Figures 1 through 4. What is the most appropriate treatment for the fracture below the implant?
. Balanced traction to address concern for persistent infection with reoperation
. Open reduction and internal fixation of the fracture with a lateral plate and screws
. Removal of the articulating spacer and revision to a longer-stem antibiotic-loaded articulating spacer
. Removal of the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement

Correct Answer & Explanation

. Open reduction and internal fixation of the fracture with a lateral plate and screws

Explanation

This patient has a type C periprosthetic femoral fracture. The articulating spacer is not involved in the fracture, which is well distal to the implant. The most appropriate treatment is open reduction and internal fixation of the fracture. Traction is not appropriate for this fracture because the injury can be treated surgically despite the history of previous hip infection.

Question 169

Topic: Total Hip Arthroplasty (THA)

A patient has pain 2 years after undergoing a metal-on-metal (MOM) left total hip arthroplasty (THA). Which test(s) best correlate with a prognosis if this patient is having a reaction to metal debris?

. Erythrocyte sedimentation rate, C-reactive protein, and white blood cell count
. Serum cobalt and chromium ion levels
. MRI with metal artifact reduction sequence (MARS) D. CT of pelvis

Correct Answer & Explanation

. Erythrocyte sedimentation rate, C-reactive protein, and white blood cell count

Explanation

Painful MOM THA and taper corrosion can cause substantial damage to a patient's hip if left untreated. In this case, the workup for a painful MOM THA starts the same as a workup for a painful metal-on- polyethylene bearing couple. Infection must be ruled out in every case with a set of inflammatory markers. If these markers are remotely elevated, this is an indication for joint aspiration. In patients with metal debris, the pathology report often indicates too many cells to count or cellular debris. Metal ion levels do not seem to correlate with prognosis. There are well-functioning patients with high ion levels and poor- functioning  patients  with  low  ion  levels.  Advanced  imaging  with  MARS  MRI  to  evaluate  for peritrochanteric fluid collection, a soft-tissue mass, or synovial/capsular hypertrophy will reveal signs of a metal reaction that indicate the need for a revision discussion. A CT scan can show more advanced bony destruction as an indicator of poor prognosis. These films can be used to determine the need for a structural graft or augments for reconstruction of bone loss attributable to metal debris.

Question 170

Topic: Total Hip Arthroplasty (THA)
A 45-year-old man with a painful varus knee is being considered for an upper tibial osteotomy. Which of the following factors is considered the most compelling argument against this procedure?
. Flexion contracture of 5°
. Subchondral cyst in the medial tibial condyle
. Lateral meniscal degeneration seen in an MRI scan
. Rheumatoid arthropathy
. Previous medial meniscectomy

Correct Answer & Explanation

. Rheumatoid arthropathy

Explanation

DISCUSSION: Proximal tibial osteotomy is appropriate for the younger and/or athletic patient who has mild to moderate medial compartment osteoarthritis. Relative contraindications include limited range of motion (e.g., flexion contracture of 15°), anatomic varus of greater than 10°, advanced patellofemoral arthritis, and tibial subluxation. Inflammatory arthritides involve all the compartments and are a contraindication to osteotomies around the knee. REFERENCE: Kelly MA: Nonprosthetic management of the arthritic knee, in Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 245-249.

Question 171

Topic: Total Hip Arthroplasty (THA)
A woman had a primary total hip arthroplasty 7 years ago that included a proximally coated titanium stem, a cobalt alloy femoral head, a titanium hemispherical acetabular component, and a polyethylene liner. She did well for 4 years but has now had two dislocations and reports pain and weakness around the left hip. She denies any fevers, chills, or constitutional symptoms. On examination, the patient walks well without any signs of an antalgic or Trendelenburg gait. Her abductor mechanism demonstrates good strength. Her erythrocyte sedimentation rate and C-reactive protein level are normal. On radiographs, all components appear well fixed and in good alignment. What is the most appropriate treatment at this time?
. Physical therapy to improve hip stability
. Use of an abduction brace to limit the patient’s range of motion
. Conversion to a constrained acetabular liner
. Cobalt and chromium serum metal ion level testing

Correct Answer & Explanation

. Cobalt and chromium serum metal ion level testing

Explanation

DISCUSSION: Trunnionosis is a recently recognized complication following total hip arthroplasty and can occur when a cobalt alloy femoral head is used on a titanium alloy or cobalt alloy femoral stem. Patients often present with pain or swelling around the hip but at times can present with instability. Certain femoral stem designs have been associated with increased reports of trunnionosis. In a patient with a cobalt alloy femoral head who presents with instability, swelling, and weakness around the hip, the potential for trunnionosis and an adverse local tissue reaction should be considered.

Question 172

Topic: Total Hip Arthroplasty (THA)
Examination of a 30-year-old professional singer who has persistent neck and shoulder pain reveals a positive Hoffman’s sign and clonus because of anterior C2-3 cord compression. The MRI scan shown in Figure 11a and the cervical CT scan shown in Figure 11b reveal focal anterior cord compression at the C2-3 level. Which of the following surgical approaches would least affect her professional career?
. Transoral, transmucosal direct anterior approach to C2-3
. Left-sided anterior approach to C2-3 (Smith-Robinson)
. Right-sided posterior retropharyngeal approach to C2-3 (Whitesides)
. Right-sided anterior approach to C2-3 (Smith-Robinson)
. Right-sided anterior retropharyngeal approach with extended vertical incision (superior extension Smith-Robinson)

Correct Answer & Explanation

. Right-sided anterior retropharyngeal approach with extended vertical incision (superior extension Smith-Robinson)

Explanation

Protection of the superior laryngeal nerve is critical in a professional singer. The nerve is easily injured with retraction when using vertical extension of common anterior surgical approaches to gain exposure to the C2-3 level. McAfee and associates reported on 17 patients with C1-2 and C2-3 pathology. They used a modified submandibular approach as an anterior retropharyngeal exposure with modification of the superior extension of the Smith-Robinson technique that allows visualization of the superior laryngeal nerve and surrounding structures. No incidences of superior laryngeal nerve injury were recorded. The transoral approach should be avoided because of the high rate of infection and limited exposure.

Question 173

Topic: Total Hip Arthroplasty (THA)

In the treatment of thoracolumbar idiopathic scoliosis using an anterior single rod technique with interbody cages, which of the following variables has been associated with pseudoarthrosis. Review Topic

. Thoracic curve coronal correction of > 40%
. Thoracolumbar/lumbar curve coronal correction > 50%
. Smaller adolescents (<50 kg)
. Failure to maintain lumbar lordosis of > 45 degrees
. Thoracic hyperkyphosis (>40 degrees )

Correct Answer & Explanation

. Thoracic curve coronal correction of > 40%

Explanation

In select patients with thoracolumbar idiopathic scoliosis, an anterior approach with a single rod and interbody cages may be indicated. Thoracic hyperkyphosis (>40 degrees ) is a risk factor for pseudoarthrosis in patients treated with this method.In a prospective study, Sweet et al found anterior instrumented fusions using a single solid rod had good radiographic and clinical outcomes. In their treatment group they found common risk factors for pseudarthrosis were smoking, weight >70 kg, and T5-T12 hyperkyphosis of > 40 degrees. They recommend consideration should be given to alternate techniques in larger adolescents (>70 kg) with thoracic hyperkyphosis (>40 degrees ). The average coronal correction of thoracic curves was from 55 degrees to 29 degrees (47%). The average correction of thoracolumbar/lumbar curves was from 50 degrees to 15 degrees (70%). Neither of these variables were associated with pseudoarthrosis. In the sagittal plane, lordosis was maintained in thoracolumbar/lumbar fusions at -58 degrees (T12-sacrum). Improved maintenance of lumbar lordosis is considered one of the advantages of an anterior approach.In an additional study from the same group at Wash U, Hurford et al designed a study to compare the results of anterior DUAL-rod instrumentation with their previous experience using single-rod constructs. They found the two technique were comparable in the amount of radiographic deformity correction obtained. However, they report the absence of any pseudarthroses in the 60 patients with dual-rod is a distinct advantage over the single rod technique.

Question 174

Topic: Total Hip Arthroplasty (THA)

A 68-year-old female presents with an unstable THA. She has dislocated posteriorly 3 times in the past month. Radiographs demonstrate well-fixed implants with the acetabular component at 40 degrees of inclination and 15 degrees of anteversion. The femoral stem is well-fixed in 15 degrees of anteversion. What is the most appropriate surgical intervention?

. Revision of the acetabular component to increase anteversion
. Revision of the femoral component to increase anteversion
. Exchange of the modular head to a longer neck length
. Conversion to a dual-mobility articulation
. Application of a hip abduction brace for 12 weeks

Correct Answer & Explanation

. Revision of the acetabular component to increase anteversion

Explanation

For recurrent instability with acceptable component positioning and well-fixed implants, conversion to a dual-mobility construct is highly effective. It increases the jump distance and the effective head size, reducing dislocation risk.

Question 175

Topic: Total Hip Arthroplasty (THA)

A 60-year-old man undergoes an uncemented THA via a direct anterior approach. Postoperatively, he complains of localized numbness and burning pain over the anterolateral aspect of his thigh. This complication is most likely due to injury to a nerve that courses between which of the following intervals?

. Tensor fasciae latae and gluteus medius
. Sartorius and tensor fasciae latae
. Rectus femoris and vastus lateralis
. Adductor longus and gracilis
. Iliopsoas and pectineus

Correct Answer & Explanation

. Tensor fasciae latae and gluteus medius

Explanation

The lateral femoral cutaneous nerve is highly at risk during the direct anterior approach to the hip. The superficial surgical interval for this approach is between the sartorius and the tensor fasciae latae.

Question 176

Topic: Total Hip Arthroplasty (THA)

Which of the following intraoperative surgical techniques most significantly decreases the risk of postoperative dislocation following a primary THA performed via a posterior approach?

. Use of a 28-mm femoral head
. Meticulous repair of the posterior capsule and short external rotators
. Preserving the ligamentum teres
. Anteverting the acetabular cup to 50 degrees
. Lengthening the limb by 2 cm

Correct Answer & Explanation

. Use of a 28-mm femoral head

Explanation

Enhanced soft tissue repair, specifically the robust reattachment of the posterior capsule and short external rotators, has been definitively shown to significantly reduce the dislocation rate in the posterior approach.

Question 177

Topic: Total Hip Arthroplasty (THA)

A 45-year-old active female undergoes THA with a ceramic-on-ceramic bearing. At 2 years postoperatively, she complains of a loud, reproducible squeaking noise from her hip during normal gait. Which of the following is the most established biomechanical cause for this phenomenon?

. Acetabular component malposition leading to edge loading
. Isolated excessive femoral offset
. Decreased femoral anteversion alone
. Subsidence of an undersized femoral stem
. Use of a 36-mm instead of a 32-mm ceramic head

Correct Answer & Explanation

. Acetabular component malposition leading to edge loading

Explanation

Squeaking in ceramic-on-ceramic THA is heavily associated with edge loading, typically caused by acetabular component malposition (e.g., steep inclination or excessive anteversion/retroversion). This leads to stripe wear and disruption of fluid-film lubrication.

Question 178

Topic: Total Hip Arthroplasty (THA)

A 55-year-old female presents with anterior groin pain 1 year after an uncemented THA. The pain is exacerbated by active hip flexion. Radiographs demonstrate that the acetabular component is placed with 10 degrees of anteversion and overhangs the anterior acetabular rim by 12 mm. Image-guided injection of the psoas bursa temporarily resolves her pain. What is the most appropriate definitive management?

. Iliopsoas tenotomy at the lesser trochanter
. Revision of the acetabular component
. Revision of the femoral component to increase lateral offset
. Hip arthroscopy and labral debridement
. Endoscopic gluteus medius repair

Correct Answer & Explanation

. Iliopsoas tenotomy at the lesser trochanter

Explanation

While iliopsoas tenotomy is an option for functional impingement, an anterior component overhang greater than 8 mm is a structural cause of psoas impingement. Revision of the malpositioned acetabular cup is required for definitive resolution.

Question 179

Topic: Total Hip Arthroplasty (THA)
  • A 45-year-old man sustains the shoulder injury shown in the radiographs in Figure 55a and 55b and the CT scan in Figures 55c and 55d. Management should consist of
. a sling and swathe, with pendulum exercises in 10 days
. open reduction and internal fixation through an anterior approach
. open reduction and internal fixation through a posterior approach
. immobilization with a splint in 45 degrees of abduction for 6 weeks
. arthroscopically assisted reduction and percutaneous screw fixation

Correct Answer & Explanation

. a sling and swathe, with pendulum exercises in 10 days

Explanation

Displaced intra-articular fractures of the glenoid fossa, as in this case, are best treated with open reduction and internal fixation through a posterior approach. ORIF through an anterior approach is very difficult and is not recommended. Significant disabilities are seen if these fractures are treated conservatively including chronic instability and DJD..............................................................

Question 180

Topic: Total Hip Arthroplasty (THA)
Radiographs show a morbidly obese man who underwent left total hip replacement 7 years ago and did well, with no symptoms prior to the current presentation. He recently rose from a seated position and felt a pop in the hip, with immediate pain and inability to bear weight. Any pressure on the left foot now produces a painful, grinding sensation with loss of left hip stability. What is the best next step?
. Revision of the acetabular implant to a constrained bearing with modular exchange of the femoral head and neck
. Revision of the acetabular and femoral implants
. Retention of the acetabular implant with modular exchange of the femoral head and neck
. Revision of the femoral component alone with a new ceramic head

Correct Answer & Explanation

. Revision of the acetabular and femoral implants

Explanation

The modular femoral stem has fractured. Revision of the acetabular implant is appropriate because of the potential for damage to the existing cup from metal debris and femoral implant contact and to convert from a metal-on-metal articulation. Retention of the femoral stem is not recommended because of the concern for failure with only a neck exchange. Revision of both components is necessary.

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