How to diagnose a prosthetic hip dislocation

The hip is a ball-and-socket joint, where the ball is the femoral head and the socket is the acetabulum.

Dislocation of a normal hip is pretty unusual. It takes a tremendous amount of force, usually a high-speed car accident. On the other hand, patients who have had hip replacement surgery can dislocate their artificial hips with minimal force, such as rolling out of bed, or getting out of a chair. These dislocations typically happen in the first four months after surgery, and most artificial hip dislocations are posterior.

Physical signs of a prosthetic hip dislocation

Dislocation of the hip forces the femoral head of the prosthesis out of the acetabulum and behind it. As a result, there are four physical signs to look for:

1. Patient’s affected leg appears shortened
2. Leg is flexed at the knee
3. Hip is internally rotated
4. Hip is adducted

Diagnostic tests for a prosthetic hip dislocation

You can confirm the diagnosis with an x-ray. On the x-ray, the femoral head is displaced out of the socket. This is best seen in the lateral view.

Excellent work! You now know the basics for diagnosing a prosthetic hip dislocation.