Review Question - QID 4509

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THA Revision Etiology Indications QID: 4509 (OBQ12.149)

QID 4509 (Type "4509" in App Search)

A 91-year-old male with a history of chronic leukemia and dementia falls and sustains the hip fracture shown in Figure A. He undergoes a hemiarthroplasty through a posterior approach. A post-operative radiograph is shown in Figure B. Three weeks later he dislocates the hip arising from the toilet seat. A radiograph is shown in Figure C. The patient undergoes a closed reduction and is placed in a hip abduction brace. Post reduction radiograph is shown in Figure D. One month later he returns to clinic complaining of pain and inability to bear weight through the leg. A radiograph of the hip is included in Figure E. Which of the following factors has MOST likely contributed to the instability of the hip hemiarthroplasty?

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Femoral stem subsidence

82/5063

Increased offset

11%

568/5063

Inadequate femoral stem neck length

13%

650/5063

Patient's dementia status

73%

3682/5063

Patient's gender

36/5063

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The most likely contributing factor to the instability include the patient's dementia.

Sultan et al use a basic science model to show liners with elevated rims placed in the posterior superior quadrant allow greater range of motion to dislocation than standard liners. They also show that 32 mm heads have greater range of motion to dislocation compared to 28 mm heads.

Morrey et al reviewed a series of 19,680 primary THA's for late dislocation (first dislocation greater than 5 years after surgery). 165 hips (0.8%) had a late dislocation. Factors associated with late dislocation include implant malposition, neurologic decline, trauma, and polyethylene wear.

Figure A shows a femoral neck fracture. Figures B and D show a hip hemiarthroplasty in appropriate position. Figure C and E show a dislocated hip hemiarthroplasty

This patient's instability was managed by converting the hip hemiarthroplasty to a total hip arthroplasty with a constrained liner as shown in illustration A. No further instability episodes occurred following the revision.

Incorrect Answers:
Answer 1: There is no evidence of femoral neck subsidence on any of these radiographs.
Answer 2: Increased offset would not lead to an increased risk of hip dislocation.
Answer 3: Post-operative radiographs suggest that the native femoral neck length has been re-established adequately.
Answer 5: Females have higher rates of dislocation than males.

ILLUSTRATIONS: