Background: Mobile-bearing knee designs represent an alternative to conventional fixed-bearing total knee arthroplasty. We present the results of a prospective, intermediate-term clinical follow-up study of the bicruciate ligament-sacrificing porous-coated Low Contact Stress rotating-platform total knee design.
Methods: Between February 1984 and January 1994, 528 uncemented primary knee replacements were performed in 421 patients. All patellae were resurfaced with use of the Low Contact Stress rotating patellar component. The average age of the patients at the time of the index procedure was sixty-nine years. The study group included 261 women and 160 men. Patients were evaluated at three months, six months, and yearly thereafter with use of the 100-point New Jersey Orthopaedic Hospital knee-scoring system. In addition, a radiographic analysis of the tibial, femoral, and patellar components was performed at each interval.
Results: There were twenty-nine failures that resulted in revision. The Kaplan-Meier estimate of implant survival at twelve years was 89.5% (95% confidence interval, 83.4% to 95.6%). The total clinical scores improved significantly compared with the preoperative scores for the first twelve months postoperatively and then plateaued. Three hundred and twenty-one knees had adequate radiographic follow-up (average, 8.1 years; range, five to twelve years). Zonal radiographic analysis revealed ninety-three instances of radiolucent lines (eighty-two of which measured <1 mm in width), with the greatest number of radiolucent lines (thirty-nine) being located around the tibial tray stem. None of these lines were deemed to be progressive, and no knee with a radiolucent line that measured >2 mm was revised because of failure.
Conclusions: This first-generation uncemented, mobile-bearing, bicruciate ligament-sacrificing knee replacement was associated with a good survival rate and demonstrated clinical efficacy during the five to twelve-year follow-up interval. .