Instability after total hip arthroplasty.

The most statistically significant risk factors for hip dislocations following total hip arthroplasty include prior hip surgery, trochanteric nonunion, and posterior surgical approach. Reoperation is required in only about one third of those patients who sustained dislocations. The most reliable surgical procedure is reorientation of the retroverted acetabular component. Care should be exercised to define the precise cause of the instability to plan the surgery that best addresses this particular problem.