Abstract
Metal-polycarbonate urethane (MPU) bearing is a cutting-edge new bearing technology for hip reconstruction. It consists of a 3mm-thick pliable acetabular cup which biomechanically mimics human cartilage and can be coupled with large diameter metal heads. In pristine sockets, no acetabular bone reaming is required to insert the cup. No cement is needed and the cup is simply snapped by hand into a groove made with a special tool. In deformed sockets, the standard reaming technique must be used. The cup acts as a liner inserted into an uncemented metal shell.
MPU bearing has been analysed in comparative in vitro studies. Clinical and radiographic results have been recorded at a minimum follow-up of 2 years in 202 femoral neck fracture patients.
Polycarbonate-urethane elasticity is 20MPa (70 times less than UMHWPE, 10,500 times less than CoCr, p < 0.001). The number of particles generated per step is 1000 with MPU, 1,000,000 with ceramic-ceramic and metal-metal (MOM) (p< 0.001). Fluid film thickness is 0.25microns with MPU, 0.02 with MOM (p< 0.001). At a minimum follow-up of 2 years, X-rays showed good implant stability. In sockets where the buffer alone was implanted an improvement of the supraacetabular bone density was observed over time. Mean Harris hip score after 1 month was 58 points, increasing to 80 points at 2 years (p < 0.05). One patient was revised, due to non-implant-related pain.
The in vitro and clinical data support the use of this novel bearing technology which has the potential to revolutionize hip arthroplasty.
Correspondence should be addressed to: EFORT Central Office, Technoparkstrasse 1, CH – 8005 Zürich, Switzerland. Tel: +41 44 448 44 00; Email: office@efort.org
Author: Antonio Moroni, Italy
E-mail: a.moroni@ior.it
