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Total Hip Arthroplasty (THA) MCQs

Practice Set 7 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 121

Topic: Total Hip Arthroplasty (THA)

A 32-year-old male presents for evaluation of progressive genu varum. Preoperative planning requires a full-length standing anteroposterior (AP) radiograph of the lower limbs. The radiologic technologist positions the patient with their feet pointing straight forward, ensuring the X-ray beam is centered appropriately. However, the surgeon notes that the patellae appear internally rotated on the initial film. According to Paley's principles, what is the most likely consequence of this rotational error?

. The Mechanical Axis Deviation (MAD) will be underestimated, leading to undercorrection.
. The Joint Orientation Angles (e.g., mLDFA, MPTA) will be accurately measured, but the CORA will be misplaced.
. The frontal plane projection of the knee joint will be distorted, rendering joint orientation angle measurements inaccurate.
. The leg length discrepancy will be exaggerated, requiring additional compensatory blocks.
. The sagittal plane deformity will be masked, leading to an incorrect assessment of procurvatum or recurvatum.

Correct Answer & Explanation

. The frontal plane projection of the knee joint will be distorted, rendering joint orientation angle measurements inaccurate.

Explanation

Correct Answer: CThe case explicitly states that the 'Patella-Forward Rule' is the single most critical parameter in radiographic acquisition. Aligning the feet forward when there is inherent femoral anteversion or tibial torsion can induce significant rotation at the knee. This rotation distorts the frontal plane projection, making all subsequent joint orientation angle measurements (like the mLDFA and MPTA) completely inaccurate. The patella-forward position ensures a true AP view of the knee joint, which is essential for accurate frontal plane analysis.Option A is incorrectbecause while an inaccurate frontal plane projection can lead to errors in MAD calculation and subsequent under/overcorrection, the primary and direct consequence of rotational error at the knee is the distortion of joint orientation angles, which then cascades to MAD errors. The statement focuses on the direct impact.Option B is incorrectbecause the text clearly states that rotation 'distorts the frontal plane projection, rendering all subsequent joint orientation angle measurements completely inaccurate.' Therefore, the mLDFA and MPTA would not be accurately measured.Option D is incorrectbecause rotational alignment primarily affects frontal plane angular measurements, not leg length discrepancy. LLD is assessed by the overall length and is compensated by blocks to level the pelvis, independent of knee rotation.Option E is incorrectbecause rotational errors primarily affect frontal plane assessment. Sagittal plane deformities (procurvatum/recurvatum) are assessed on lateral views or by specific techniques to overcome their distortion on AP views, but they are not directly masked by a rotational error in the AP view itself in the manner described.

Question 122

Topic: Total Hip Arthroplasty (THA)

A 50-year-old patient with a complex multiplanar deformity of the distal femur is undergoing preoperative planning. The surgeon obtains a standard full-length standing AP radiograph. However, the patient has a significant sagittal plane deformity (procurvatum) at the knee. According to Paley's principles, what is the primary concern regarding the interpretation of this AP radiograph?

. The Mechanical Axis Deviation (MAD) will be accurately represented, but joint line obliquity will be exaggerated.
. The radiograph will appear highly distorted, making accurate assessment of frontal plane angles unreliable.
. The patella-forward rule cannot be applied, leading to inevitable rotational errors.
. The leg length discrepancy will be underestimated due to the sagittal plane component.
. The Sugioka view will be required to correct for the sagittal plane distortion.

Correct Answer & Explanation

. The radiograph will appear highly distorted, making accurate assessment of frontal plane angles unreliable.

Explanation

Correct Answer: BThe text specifically addresses this scenario under 'Overcoming Distortion in Sagittal and Frontal Plane Deformities': 'When there is a significant sagittal plane component of deformity (such as severe procurvatum or recurvatum), an AP view radiograph obtained in the usual fashion will appear highly distorted.' This distortion makes accurate assessment of frontal plane angles and overall alignment unreliable.Option A is incorrectbecause the text states the AP view will be 'highly distorted,' implying that the MAD and other frontal plane measurements will be unreliable, not accurately represented.Option C is incorrectbecause while a severe sagittal deformity can make positioning difficult, the patella-forward rule is about rotational alignment in the transverse plane, not directly about sagittal plane distortion on an AP view. The issue here is the projection of a sagittal deformity onto the frontal plane.Option D is incorrectbecause sagittal plane deformity primarily affects the projection of angular alignment in the frontal plane, not directly the measurement of leg length discrepancy.Option E is incorrectbecause the Sugioka view is for assessing proximal femoral deformities in the sagittal plane (true lateral of the femoral neck), not for correcting distortion caused by knee procurvatum/recurvatum on a full-length AP view. Specialized techniques for sagittal plane deformities would involve true lateral films or specific beam angulation, not the Sugioka view.

Question 123

Topic: Total Hip Arthroplasty (THA)

In pre-operative planning for deformity correction, the Joint Line Convergence Angle (JLCA) is measured. What is its normal value, and what does an abnormally increased JLCA typically indicate?

. Normal is 0-2 degrees; increased indicates ligamentous laxity or cartilage loss
. Normal is 5-7 degrees; increased indicates bony deformity
. Normal is 0-2 degrees; increased indicates femoral shaft bowing
. Normal is 3-5 degrees; increased indicates rotational malalignment
. Normal is 8-10 degrees; increased indicates leg length discrepancy

Correct Answer & Explanation

. Normal is 0-2 degrees; increased indicates ligamentous laxity or cartilage loss

Explanation

The normal JLCA is 0 to 2 degrees. An increased JLCA suggests intra-articular pathology, such as asymmetric cartilage loss or collateral ligament laxity.

Question 124

Topic: Total Hip Arthroplasty (THA)
A 59-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

DISCUSSION: 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 125

Topic: Total Hip Arthroplasty (THA)

You are planning a deformity correction for a patient with a tibial malunion. During pre-operative templating, you determine the Center of Rotation of Angulation (CORA). If you perform your closing wedge osteotomy at a level proximal to the CORA and only correct the angular deformity (without any translation at the osteotomy site), what will be the effect on the mechanical axis?

. Complete and anatomic correction of the mechanical axis
. Secondary translational deformity of the bone and mechanical axis
. Significant leg length discrepancy due to shortening
. Reversal of the joint line orientation
. Induction of a rotational deformity

Correct Answer & Explanation

. Secondary translational deformity of the bone and mechanical axis

Explanation

According to the rules of osteotomy formulated by Paley: If an osteotomy is performed at the CORA, angulation corrects the deformity fully. If the osteotomy is performed at a level different from the CORA, correcting the angular deformity without concurrent translation at the osteotomy site will result in a secondary translational deformity (the anatomical axis will end up with a zigzag or parallel shift).

Question 126

Topic: Total Hip Arthroplasty (THA)
A 14-year-old girl with a 4 cm leg length discrepancy is being evaluated for an intramedullary motorized magnetic lengthening nail. Which of the following is an absolute contraindication to utilizing this specific device technology?
. History of prior external fixation on the contralateral leg
. Leg length discrepancy greater than 3 cm
. Expected postoperative need for frequent MRI screening
. Presence of a closed proximal tibial physis
. Concurrent administration of oral contraceptives

Correct Answer & Explanation

. Expected postoperative need for frequent MRI screening

Explanation

Motorized magnetic lengthening nails (such as the PRECICE nail) contain complex internal magnetic driving mechanisms. Placing a patient with this device into a Magnetic Resonance Imaging (MRI) scanner can lead to implant demagnetization, spontaneous lengthening or shortening, and implant heating or failure. Thus, an absolute requirement for ongoing MRI studies (e.g., for tumor surveillance) is an absolute contraindication for a magnetic lengthening nail.

Question 127

Topic: Total Hip Arthroplasty (THA)

In a metal-on-polyethylene Total Hip Arthroplasty, what specific design factor significantly increases the risk of mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction?

. Use of a highly cross-linked polyethylene liner
. Decreased femoral offset
. Use of a ceramic femoral head
. Increased femoral head diameter
. Use of an uncemented femoral stem

Correct Answer & Explanation

. Increased femoral head diameter

Explanation

Mechanically assisted crevice corrosion (MACC), or trunnionosis, is mediated by micromotion and fretting at the taper junction between the stem and the modular head. The use of larger diameter femoral heads (e.g., >36 mm) increases the frictional torque and lever arm acting on the head-neck junction during gait, significantly increasing the risk of trunnionosis. Ceramic heads are essentially inert and reduce the risk of corrosion.

Question 128

Topic: Total Hip Arthroplasty (THA)

In the preoperative planning for a high tibial osteotomy to correct a varus deformity, the surgeon applies Osteotomy Rule 1. According to this principle, what is the expected geometric outcome if both the osteotomy cut and the mechanical hinge are located exactly at the center of rotation of angulation (CORA)?

. Pure angulation without translation
. Angulation with simultaneous medial translation
. Pure translation without angulation
. Angulation with simultaneous lateral translation
. Correction of both angulation and leg length discrepancy

Correct Answer & Explanation

. Pure angulation without translation

Explanation

Osteotomy Rule 1 states that if the osteotomy and the mechanical hinge are both placed at the CORA, the bone ends will angulate purely without any translational deformity.

Question 129

Topic: Total Hip Arthroplasty (THA)

A 54-year-old male who underwent a ceramic-on-ceramic total hip arthroplasty 3 years ago reports a loud, audible squeaking sound from his hip when walking or bending. What acetabular component orientation is most strongly associated with the onset of this specific phenomenon?

. High cup inclination and high cup anteversion
. Low cup inclination and low cup anteversion
. High cup inclination and retroversion
. Low cup inclination and excessive medialization
. Neutral cup alignment with a 36-mm head

Correct Answer & Explanation

. High cup inclination and high cup anteversion

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading of the components. Edge loading most frequently occurs when the acetabular cup is placed in excessive inclination (steep angle) and excessive anteversion.

Question 130

Topic: Total Hip Arthroplasty (THA)

A patient has a painful metal-on-metal (MOM) left total hip arthroplasty (THA). Which test(s) best correlate with 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
. Metal artifact reduction sequence (MARS) MRI
. CT scan of pelvis

Correct Answer & Explanation

. Metal artifact reduction sequence (MARS) MRI

Explanation

DISCUSSIONPainful 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 131

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)
. 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 132

Topic: Total Hip Arthroplasty (THA)
A 63-year-old 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

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 133

Topic: Total Hip Arthroplasty (THA)
Which of the following factors increases the risk of sciatic nerve injury in primary total hip arthroplasty (THA)?
. Male gender
. Anterolateral approach
. Posterior superior quadrant acetabular screw placement
. Osteonecrosis
. Developmental dysplasia of the hip

Correct Answer & Explanation

. Developmental dysplasia of the hip

Explanation

DISCUSSION: Injury to the sciatic nerve is a relatively rare but serious complication of THA. Dissection of the sciatic nerve is not typically done during primary THA, although the nerve can be identified during the surgical approach. An anterolateral approach to THA would not necessarily be associated with any greater incidence of sciatic nerve injury than other approaches. Screw fixation for the acetabular component is often a matter of surgeon preference. Provided that the anatomic safe zones for screw fixation (posterior inferior and posterior superior) are recognized, injury to the sciatic nerve from acetabular screws can be minimized. Restoration of anatomic length is important in primary THA. Overlengthening can result in sciatic nerve palsy. Developmental dysplasia of the hip can lead to a congenitally shortened extremity with concomitant congenital shortening of the associated neurovascular structures. Overlengthening of the extremity during THA for developmental dysplasia of the hip can lead to sciatic palsy. Osteonecrosis is not an associated risk factor for sciatic nerve palsy. REFERENCES: DeHart MM, Riley LH Jr: Nerve injuries in total hip arthroplasty. J Am Acad Orthop Surg 1999;7:101-111. Anas P, Felix B: Evaluation and prevention of postoperative complications, in Neurologic Injury in Revision THA. New York, NY, Springer Verlag, 1999, pp 361-371.

Question 134

Topic: Total Hip Arthroplasty (THA)
A 68-year-old man presents with chronic progressive right shoulder pain and loss of motion. He has active shoulder elevation of 120° and 5-/5 shoulder forward flexion strength limited by pain. He has exhausted nonsurgical management over the past year and is now interested in surgical intervention. Figure 1 is the preoperative axial CT scan of his shoulder. During surgical reconstruction, the surgeon should anticipate the location of maximal glenoid erosion to be?
. Posterior
. Anterior
. Superior
. Inferior

Correct Answer & Explanation

. Posterior

Explanation

In patients with chronic progressive shoulder pain and glenohumeral osteoarthritis, the humeral head typically subluxates posteriorly, leading to maximal glenoid erosion in the posterior quadrant.

Question 135

Topic: Total Hip Arthroplasty (THA)
Figure 29 shows the radiograph of a 55-year-old patient who has recurrent total hip dislocation. Dislocation is most likely to occur in this patient when the hip is in which of the following positions?
. Neutral rotation
. External rotation
. Internal rotation
. Hyperflexion
. Midstance phase of gait

Correct Answer & Explanation

. Internal rotation

Explanation

DISCUSSION: The patient has an acetabular component that is placed in excessive anteversion; this is confirmed by the shoot-through radiograph. The most common reasons for dislocation of a total hip replacement include inappropriate positioning of the components, inadequate abductor tension, or impingement. Implants placed without adequate total anteversion tend to dislocate posteriorly, and implants with excessive anteversion tend to dislocate anteriorly. Superior dislocations can occur if the acetabular component is placed in a severely vertical position with inadequate lateral coverage. REFERENCE: Paterno SA, Lachiewicz PF, Kelley SS: The influence of patient-related factors and the position of the acetabular component on the rate of dislocation after total hip replacement. J Bone Joint Surg Am 1997;79:1202-1210.

Question 136

Topic: Total Hip Arthroplasty (THA)

A 55-year-old male presents with audible squeaking from his total hip arthroplasty, performed three years ago using a ceramic-on-ceramic bearing. Which of the following component malpositions is most strongly associated with the development of this specific acoustic phenomenon?

. Acetabular cup retroversion
. Acetabular cup inclination > 50 degrees
. Femoral stem retroversion
. Excessive femoral offset
. Acetabular cup inclination < 30 degrees

Correct Answer & Explanation

. Acetabular cup retroversion

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which occurs with a steeply positioned acetabular cup (inclination > 50 degrees) or excessive anteversion. This leads to disruption of fluid-film lubrication and localized stripe wear.

Question 137

Topic: Total Hip Arthroplasty (THA)

Varus intertrochanteric osteotomy for coxa valga commonly produces which of the following results?

. Decreased abductor lever arm
. Increased hip joint reaction force
. Increased center edge angle
. Abductor lag and lurch
. Lengthening of the leg

Correct Answer & Explanation

. Decreased abductor lever arm

Explanation

DISCUSSION: The greater trochanter is raised as a by-product of varus osteotomy, and a temporary abductor lag and lurch is common for 6 months following surgery.  In the absence of hip joint subluxation, varus intertrochanteric osteotomy has no effect on the center edge angle of Wiberg.  Varus osteotomy typically increases femoral offset, thereby improving the abductor lever arm and reducing the hip joint reaction force.  Even without taking a wedge, varus osteotomy always produces some degree of shortening.REFERENCE: Millis MB, Murphy SB, Poss R : Osteotomies about the hip for the prevention and treatment of osteoarthrosis.  Instr Course Lect 1996;45:209-226.

Question 138

Topic: Total Hip Arthroplasty (THA)

The patient is given a blood transfusion. After starting the transfusion, nurses note that her temperature is 38.8°C and she has shaking and chills. What is the most likely cause of this problem?

. Bacterial contamination of intravenous tubing
. Transmission of the hepatitis virus
. Reaction to Kidd antigen in transfused blood
. Blood transfusion incompatibility

Correct Answer & Explanation

. Blood transfusion incompatibility

Explanation

DISCUSSIONBlood management and venous thromboembolism prevention are important considerations in the perioperative management of THA. Recommendations now focus on presurgical optimization of hemoglobin, use of antifibrinolytics intrasurgically, and minimized use of transfusions. Current recommendations do not favor autologous blood donation for patients with hemoglobin levels higher than 13 g/dL. There is a move toward increased use of aspirin for venous thromboembolism prophylaxis, but this modality can cause GI bleeding that may necessitate blood transfusion. Transfusion reactions are rare, and the most common cause is administration of an incompatible unit because of clerical error.

Question 139

Topic: Total Hip Arthroplasty (THA)

Which of the following factors is most closely associated with early postoperative migration of “stand-alone” lumbar interbody fusion cages?

. Pseudarthrosis
. Placement of the cage through a posterior approach
. Placement of the cage laparoscopically through an anterior approach
. Use of tapered rather than cylindrical cages
. Use of BMP-2 rather than autograft in the cage

Correct Answer & Explanation

. Pseudarthrosis

Explanation

DISCUSSION: Postoperative migration of lumbar interbody fusion cages is a rare complication.  It is most commonly seen after placement of the cages through a posterior approach, with instability of the final construct.  It is not associated with the design of the cage, the type of graft used, or a resultant pseudarthrosis.REFERENCES: McAfee PC: Interbody fusion cages in reconstructive operations on the spine.  J Bone Joint Surg Am 1999;81:859-880.McAfee PC, Cunningham BW, Lee GA, et al: Revision strategies for salvaging or improving failed cylindrical cages.  Spine 1999;24:2147-2153.

Question 140

Topic: Total Hip Arthroplasty (THA)
Figures 1 and 2 show the radiographs obtained from a 68-year-old 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 and femoral implants is appropriate because of the potential for damage to the existing cup from metal debris and femoral implant contact. Retention of the femoral stem is not recommended because of the concern for failure with only a neck exchange. Femoral stem removal without osteotomy would be difficult due to the fracture of the implant's femoral neck and the inability to gain purchase for extraction.

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