Abstract
Introduction
Metal-on-polycarbonate urethane (MPU) is a cutting-edge new bearing technology for hip arthroplasty. The acetabular component consists of a 2.7mm-thick polycarbonate-urethane liner inserted into a specially manufactured uncemented titanium shell coated with hydroxyapatite [(HA) Fig. 1]. The liner is pliable and biomechanically mimics human cartilage. In vitro studies have shown minimal wear, fluid film lubrication, physiological load transmission and shock absorption capacity equal to the normal hip. This system includes prosthetic heads of a diameter 12mm less than the socket diameter. The aim of this study was to clinically assess patients treated with this novel technology in a retrospective single centre study.
Methods
Twenty-seven patients with osteoarthritis treated with MPU bearing arthroplasty were included. Mean patient age was 67.9±10.35 years (44–84). Sixteen patients were female and 11 were male. Twenty-four of these had an uncemented HA-coated stem while 3 had a hip resurfacing metal femoral component. All patients were operated on by a single surgeon using a postero-lateral approach.
Results
No patients were lost to follow-up. Mean follow-up time was 29 months (minimum 24 months). There were no major complications. At follow-up, the mean Harris hip score was 98 points (80–99). X-rays showed good bone-implant contact without any osteolysis or bone rarefaction.
Discussion and conclusion
Our promising short-term results confirm the in vitro findings. Advantages of this new bearing technology include the possibility to use large diameter metal heads without exposing the patients to elevated levels of metal ions as is the case with metal-on-metal bearings, the minimal wear and the superior biomechanical characteristics.
