Analyses of prosthesis stem failures in noncemented modular hip revision prostheses.

In recent years, hip prosthesis stem revision by means of modular revision systems has reached an essential role in revision prosthetics. It is an extremely successful technique. Reports about mechanical failure in nonmodular revision stems have already been published. This complication is rare, but feared. We report about mechanical failure of four non-cemented modular revision stems over a period of 28 months. All failures became clinically apparent because of severe inguinal or thigh pain and were confirmed by conventional x-ray imaging. All stem failures occurred just below the interface between prosthesis stem and neck, which is a biomechanically stressed area. Distal of the failure, all stems were still firmly fixed. In all cases, there was obvious evidence of loosening at the proximal component. Metallographic and energy-dispensive x-ray analysis of one stem showed a fatigue fracture due to dynamic stress. If new pain arises after revision surgery with modular non-cemented prosthesis systems, the possibility of an implant failure should be kept in mind. Patients should be informed accordingly about the risk of implant failure.