In a mobile-bearing unicondylar knee arthroplasty (UKA) stability is very important for the knee function and to prevent dislocation of the insert. A tension-guided technique to determine the position of the optimal posterior bone cut should theoretically lead to a better varus-valgus stability. The goal of this study was to measure the difference in valgus laxity in flexion and extension between a tension-guided and spacer-guided system for mobile-bearing UKA. Also clinical function was evaluated between the groups. A tension-guided UKA system (BalanSysTM, Mathys, Bettlach, Switzerland) was compared with a retrospective group of a spacer-guided system (Oxford, Biomet Ltd, Bridgend, UK). A total of 30 tension-guided UKAs were placed and compared to 35 spacer-guided prostheses. Valgus laxity was measured at least 6 months postoperatively in both groups using stress radiographs. The flexion stress radiographs were made fluoroscopically aided in 70 degrees of knee flexion. Laxity measurements in extension were performed on stress radiographs obtained with the Telos device. Knee Society Scores (KSS) were obtained at follow-up.Background
Patients and Methods
Between February 1975 and August 1976, 195 total hip replacements using Stanmore components were performed; of these, 146 were in 135 patients who had not had previous hip surgery. At review 52 had died, but none of the others was lost to follow-up. Of the 52, two had had a second operation, one for infection and one for recurrent dislocation. In the remaining 83 patients (92 hips) five revisions were necessary: four for aseptic loosening, and one for stem fracture. The remaining 78 patients had little or no pain and little restriction of activity. After a follow-up period of at least nine years, the survival rate of the prosthesis was 95%. There had been migration of the femoral component in five cases and migration of the acetabular cup in one case, but no wear of the acetabular component could be demonstrated.
