Dislocation of a total hip arthroplasty caused by iliopsoas tendon displacement.

The iliopsoas tendon was caught behind the prosthetic neck after an early anterior dislocation of a revised total hip arthroplasty. The displaced tendon caused instability with successive dislocations that necessitated open reduction. The diagnosis of iliopsoas tendon interposition should be suspected when an early anterior dislocation of a total hip arthroplasty is followed by a concentric reduction and a dramatic change in stability.