Total Hip Replacement Complication — ABOS Oral Boards Preparation
What examiners expect and how to prepare
Clinical Scenario
A 58-year-old right-hand-dominant female nurse presents to the emergency department 3 weeks after a right total hip arthroplasty performed through a posterior approach for end-stage osteoarthritis. She was doing well until today when she bent forward to pick up her grandchild and felt a pop in her right hip, followed by immediate severe pain and inability to bear weight. She reports that her leg feels short. On exam, the right lower extremity is shortened, internally rotated, and adducted. She has intact distal neurovascular function. She has no wound drainage or signs of infection.
AP pelvis radiograph confirms a posterior dislocation of the right total hip arthroplasty. The acetabular and femoral components appear well-positioned — cup abduction angle is approximately 42 degrees and anteversion appears adequate on the AP film. There is no periprosthetic fracture.
You performed closed reduction in the emergency department under procedural sedation with fluoroscopic guidance. Reduction was achieved and confirmed to be stable through a functional range of motion — stable in 90 degrees of flexion with internal rotation to 30 degrees. Post-reduction radiographs confirm concentric reduction with no fracture. CT scan obtained post-reduction shows cup anteversion of 10 degrees (low end of the safe zone) and combined anteversion of 28 degrees. You placed the patient in a hip abduction brace and counseled her on posterior hip precautions with close follow-up.
What Examiners Look For
- Data gathering: Mechanism of dislocation — posterior approach dislocations typically occur with flexion, adduction, and internal rotation. Timing and activity at the time of dislocation matter.
- Diagnosis: How do you differentiate anterior from posterior dislocation on clinical exam and radiographs? Why does this matter for management?
- Treatment plan: When is closed reduction sufficient and when should you go to the OR? What are the criteria for a stable versus unstable reduction?
- Technical skill: Describe the closed reduction technique — patient positioning, direction of force, and sedation requirements.
- Indications: What component positions constitute the safe zone, and when does a malpositioning require revision? Discuss the Lewinnek safe zone and its limitations.
- Complications: What if the hip dislocates again? Describe your algorithm — constrained liner, revision of cup position, dual-mobility bearing, or approach change.
- Applied knowledge: Discuss the dislocation rates between posterior and anterior approaches and how surgical technique mitigates risk.
Common Pitfalls
- Not measuring component position accurately — CT is the gold standard for anteversion, not plain films.
- Relying solely on the Lewinnek safe zone — recent evidence shows that patient-specific spinopelvic mechanics play a larger role.
- Not counseling the patient on hip precautions and dislocation risk modification — education is part of the treatment.
- Jumping to revision surgery after a single dislocation — most first-time dislocators can be managed with closed reduction and precautions.
- Not discussing the role of dual-mobility bearings, larger femoral heads, and constrained liners in the recurrent dislocator.
Key Classifications
Related Scenarios
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