A roentgen stereophotogrammetric analysis of unicompartmental knee arthroplasty

Roentgen stereophotogrammetric analysis (RSA) was used to investigate the stability of the tibial component in unicompartmental knee arthroplasty. Twenty patients were implanted with a Howmedica Duracon UNI prosthesis (Limerick, Ireland) and studied for an average follow-up of 30 months. In most cases, the displacements detected at 1-year follow-up were small (ie, not exceeding 0.5 mm for translations and not exceeding 1.0 degrees for rotations). Only 1 patient showed signs of mechanical loosening as the prosthesis continued to migrate, reaching 3.2 mm of total motion at 4-year follow-up. RSA did not show any deformation in the polyethylene except for the case of loosening. The clinical results were excellent and good according to the Hospital for Special Surgery scoring system. No correlation was found among demographic, clinical, and RSA data.