Volume 9, Issue 2 (February 2012)
31 Year Evolution of the Rotating-Platform Total Knee Replacment: Coping With “Spinout” and Wear
Low-contact-stress rotating-platform knee replacements were the original mobile-bearing knees developed by the senior authors in 1978 to improve fixation and minimize wear, however, 1-2 % experienced “spin-out” and wear resulting in the development of a third generation rotating platform (Buechel-Pappas, or B-P) in 1991. The purpose of this study is to evaluate design modifications incorporated into the B-P device based upon clinical outcomes. Clinical results of the initial 310 cementless B-P rotating platform total knee replacements in 257 patients were analyzed using a strict knee scoring scale. Of that group, 259 total knees in 206 patients were followed for 2–18 years (mean: 7.6 years). The titanium alloy metallic implants had a 10 μm thick titanium nitride (TiN) coating on all bearing and fixation surfaces and sintered-bead porous-coating, pore size of 350 microns, on all fixation surfaces. The rotating-platform bearing allowed 45° of internal and external rotation with further rotation limited by a stop pin on the tibial component to block complete rotary subluxation/dislocation of the bearing in the event of significant flexion instability or rotational trauma. The study showed 86.4 % excellent, 12.3 % good, 0.3 % fair, and 1.0 % poor results using a strict knee scoring scale. Complications requiring revision included tibial component loosening in 2 super-obese (BMI >50), osteoarthritic patients (0.6%) and 1 late deep infection (0.3%) in a rheumatoid patient after 3.3 years. There were no cases of bearing wear, subluxation, or dislocation seen. Radiographic analysis, using >2 mm lucency in any implant zone, demonstrated 0 % of radiolucencies around femoral components, 2.6 % around tibial components, and 0 % around patella components. Survivorship, using an end point of revision for wear or component loosening was 99.4 % at the 18-year interval.