The bisurface total knee replacement: A unique design for flexion - Four-to-nine-year follow-up study

Background: The Bisurface knee prosthesis was designed in 1989 to improve k nee flexion without affecting the durability of the prosthesis. The prosthe sis has a unique ball-and-socket joint in the midposterior portion of the f emoral and tibial components, which functions as a posterior Stabilizing ca m mechanism and causes femoral: rollback, The femoral component was made of alumina ceramic, The purpose of this study was to review the clinical resu lts of the first 223 arthroplasties performed with this prosthesis in order to assess whether this new implant had achieved its design objectives. Methods: From December 1989 to May 1994, all patients who were scheduled fo r primary total knee arthroplasty were enrolled in a prospective study of t he Bisurface: knee. The patients were evaluated clinically according to The Hospital for Special Surgery knee-rating-system and with a self-administer ed questionnaire, and they were evaluated radiographically according to the system of the Knee Society. Kaplan-Meier survivorship analysis was perform ed,vith revision of the knee or recommendation for revision as the end poin t. Results: One hundred and sixty-six patients treated with a total of 223 con secutive primary total knee arthroplasties were enrolled in the study, and 182 knees were followed for 3.9 to 9.0 years (mean, 5.8 years). Preoperativ ely, the mean Hospital for Special Surgery knee scope was 44.5 points. At t he time of latest followup, the mean knee score was 86.3 points. The mean p reoperative and postoperative ranges of flexion were 119 and 124 degrees, r espectively. The patients, even those with. a good preoperative range of mo tion, rarely lost deep flexion of the knee after the procedure. A revision operation was performed in eight knees (because of infection in five, insta bility in two, and breakage of the peg of the patellar component in one). T wo knees had recurrent medial-lateral subluxations of the femorotibial arti culation, which were treated nonoperatively, No prosthesis had loosened ase ptically and no alumina ceramic femoral component had broken by the time of latest follow-up. The rate of survival of the implant was 94 percent (95 p ercent confidence interval, 90 to 98 percent) at six years. According to th e patient questionnaires, 20 percent of the knees sometimes felt loose in d aily living activities, which prompted us to improve the intrinsic stabilit y of the prosthesis by improving the congruity of the ball-and-socket joint . Conclusions: Total knee arthroplasty with the Bisurface prosthesis resulted in an excellent range of motion and a high level of satisfaction with the operation; the durability of the prosthesis is promising.