Total Hip Arthroplasty (THA) MCQs

During a primary THA, accurate acetabular component positioning is critical to prevent dislocation. According to the classic Lewinnek 'safe zone', what are the optimal target angles for acetabular cup inclination (abduction) and anteversion, respectively?

A 60-year-old male presents with groin pain and a palpable mass 6 years after a primary metal-on-polyethylene total hip arthroplasty. He received a titanium stem with a 36-mm cobalt-chromium head. Inflammatory markers are normal, and joint aspiration reveals no growth. MRI shows a cystic mass compressing the femoral nerve. Which of the following serum metal ion profiles is most characteristic of his underlying diagnosis?

During a total hip arthroplasty, the surgeon elects to use an extended offset femoral stem instead of a standard offset stem, without changing the vertical height or leg length. What is the primary biomechanical consequence of increasing femoral offset?

A 45-year-old patient undergoes a ceramic-on-ceramic total hip arthroplasty. Three years later, the patient complains of an audible squeaking noise from the hip during ambulation. What surgical factor is most strongly associated with the development of this complication?

A surgeon is performing a THA using the direct lateral (Hardinge) approach. To protect the superior gluteal nerve, the proximal split in the gluteus medius should not extend beyond a certain distance from the tip of the greater trochanter. What is the generally accepted safe distance limit for this split?

A 45-year-old male complains of a loud 'squeaking' noise coming from his hip while walking, 4 years following a ceramic-on-ceramic THA. Which of the following biomechanical factors is most strongly associated with the development of squeaking in ceramic-on-ceramic hips?

A 70-year-old female experiences recurrent anterior dislocations of her THA. Operative notes and CT imaging indicate that the combined version (McKibbin index) of her acetabular and femoral components is significantly abnormal. Which of the following combinations of component version is most likely responsible for anterior dislocation?

A 65-year-old male with a history of multiple revision THAs presents with severe groin pain. Radiographs demonstrate an acetabular component that has migrated 3 cm superomedially. A CT scan reveals discontinuity of the anterior and posterior columns of the hemipelvis. Which of the following reconstructive options provides the most rigid mechanical fixation for pelvic discontinuity in this setting?

Dual mobility acetabular components are frequently used in revision THA to minimize the risk of dislocation. Which biomechanical principle provides the primary enhancement of stability in dual mobility constructs?

A surgeon is templating a primary total hip arthroplasty and decides to utilize a high-offset femoral stem to restore the patient's native anatomy without increasing the leg length. Biomechanically, what is the primary consequence of successfully increasing the femoral offset?

During a posterior approach to the hip (Kocher-Langenbeck), the surgeon isolates the short external rotators. To protect the blood supply to the femoral head, particularly the medial femoral circumflex artery (MFCA), where should the obturator externus tendon be transected if its release is necessary?

A 65-year-old man is undergoing a primary total hip arthroplasty (THA). The surgeon selects a high-offset femoral stem that increases femoral offset without altering leg length. Compared to a standard offset stem, what is the primary biomechanical consequence of this modification?

During a standard posterior approach (Moore/Southern) to the hip, which critical blood vessel is typically encountered near the superior border of the quadratus femoris and must be identified and coagulated to prevent significant postoperative hematoma?

When placing acetabular screws during a primary THA, the surgeon must be aware of the pelvic safe zones to avoid catastrophic neurovascular injury. Placement of a screw in the anterior-inferior quadrant places which of the following structures at highest risk?

A 55-year-old female presents with recurrent posterior dislocations following a primary THA. Radiographs demonstrate the acetabular component is placed in 10 degrees of retroversion. What is the primary biomechanical mechanism of dislocation in this specific setting?

A 45-year-old active male underwent a THA with a ceramic-on-ceramic bearing. Three years later, he complains of an audible squeaking sound during movement but denies pain. What is the most likely biomechanical etiology of this phenomenon?

During acetabular shell fixation in a primary THA, a screw is placed in the anterosuperior quadrant of the acetabulum (based on the Wasielewski quadrant system). Which vascular structure is at greatest risk of iatrogenic injury?

In preoperative templating for a primary THA, medializing the center of rotation of the acetabulum without altering femoral offset achieves which distinct biomechanical advantage?

A 45-year-old woman reports an audible 'squeaking' sound from her hip when walking, 3 years after a ceramic-on-ceramic THA. Which of the following biomechanical phenomena is most strongly associated with the onset of squeaking in these bearings?

A patient with a failed metal-on-metal THA presents with systemic symptoms, including fatigue, visual impairment, and exertional dyspnea. Laboratory testing reveals elevated serum cobalt levels. Which of the following cardiac manifestations is a recognized complication of cobalt toxicity?