Randomized Clinical Trial of Rotating-Platform and Fixed-Bearing Total Knee Arthroplasty: No Clinically Detectable Differences at Five Years

Background: For some surgeons, rotating-platform total knee designs are an intellectually appealing option to use for total knee arthroplasty because of the contention that they can self-align and accommodate small mismatches in the rotational position of the tibial and femoral components. We carried out a randomized clinical trial to determine if a posterior-stabilized, rotating-platform knee design provided better maximum knee flexion, better function, or better durability at five years of follow-up when compared with a fixed-bearing design. Methods: This randomized clinical trial of 240 primary total knee arthroplasties involved a single type of distal femoral implant (posterior-stabilized) and three different types of tibial implant (all-polyethylene fixed-bearing, modular-metal-backed fixed-bearing, and rotating-platform). The three tibial implant groups were balanced dynamically with a computerized randomization process that accounted for patient age, sex, and body mass index; surgeon; and implant type. Patients returned for examination and radiographs at three months, one year, two years, and five years postoperatively. Results: Knee range of motion was not significantly different among the all-polyethylene, modular-metal-backed, and rotating-platform tibial component groups at two years (mean, 111 degrees, 111 degrees, and 110 degrees, respectively) or five years (mean, 110 degrees, 109 degrees, and 109 degrees, respectively). Function, as measured with Knee Society scores, was not significantly different among the all-polyethylene, modular-metal-backed, and rotating-platform groups at two years (mean, 90, 91, and 91 points, respectively) or five years (mean, 88, 89, and 88 points, respectively). Stair-climbing scores were not significantly different among the three groups at two years (mean, 39, 40, and 39 points, respectively) or five years (mean, 37, 40, and 36 points, respectively). There were four revisions: one in the all-polyethylene group (patellar fracture), two in the modular-metal-backed group (aseptic loosening), and one in the rotating-platform group (deep infection). Conclusions: In this randomized clinical trial, the rotating-platform total knee design was reliable and durable but did not provide better maximum knee flexion, better function, or better durability at five years postoperatively when compared with a posterior-stabilized, fixed-bearing design incorporating either an all-polyethylene or a modular-metal-backed tibial component.