Which hip positions increase the risk of dislocation after total hip arthroplasty?

• A. Flexion with adduction and internal rotation
• B. Flexion with abduction and external rotation
• C. Extension with adduction
• D. Neutral with flexion

Answer: (A)

Dislocation after total hip arthroplasty is driven by how hip position moves the femoral head relative to the acetabular cup. The most dislocation-prone combination is hip flexion with adduction and internal rotation. In this position the femoral head lines up toward the posterior rim of the socket, and after a posterior approach the posterior capsule and short external rotators are already at risk, making it easier for the head to slip out. As a result, bending forward with the leg pulled toward the midline and rotated inward is the scenario that most commonly causes dislocation. Safer alternatives include positions with flexion plus abduction and external rotation, or neutral/slightly flexed positions, which keep the head away from the posterior rim and reduce dislocation risk.