The Bi-Surface total knee arthroplasty: Minimum 10-year follow-up study

The Bi-Surface Knee System (Japan Medical Material, Kyoto, Japan), which has a unique ball-and-socket joint and whose femoral component is made from alumina ceramic, was designed to improve deep knee flexion and long-term durability after total knee arthroplasty. The purpose of this study was to review the clinical results of a minimum 10-year follow-up. Between 1989 and 1997, 507 total knee arthroplasties were carried out in 371 patients. Forty three patients (56 knees) were lost to follow-up. The mean age of the patients at operation was 68.5 years, and the patients were followed up for a mean of 11.7 years. The knees were evaluated on the basis of Knee Society knee score and functional score, radiographs, and Kaplan–Meier survivorship analysis. The knee score was improved from 38.9 ± 17.4 points preoperatively to 93.3 ± 7.8 points at the latest follow-up ( p < 0.001). The functional score was improved from 34.9 ± 19.3 points to 52.7 ± 24.1 points ( p < 0.001). The mean range of flexion was improved from 118.7 ± 21.7° to 124.2 ± 20.8° ( p < 0.001). The critical angle, which means the border to gain more range of flexion postoperatively, was 130.1°. Kaplan–Meier survivorship at 10-year was 95.9% with any operation or radiographic failure as the end point. The corresponding rate was 97.4% with revision of any component as the end point. No ceramic component fracture occurred. The present study demonstrates that good range of flexion was maintained for a long time after total knee arthroplasty with excellent durability. The Bi-Surface Knee System appears to have achieved its design objectives.