Mobile-Bearing Knee Replacement

Durable long-term fixation has been documented for many designs of fixed-bearing total knee replacement20,30,59,69. However, in the late 1970s and the early 1980s, implant fixation and polyethylene wear became recognized as long-term causes of late failure. Mobile-bearing knee replacements, with a polyethylene insert that articulates with a metallic femoral component and a metallic tibial tray, were designed to create a dual-surface articulation. This feature was intended to reduce the surface and subsurface stress states at the bearing surfaces and at the bone-implant surfaces by maximizing the conformity of the tibial and femoral components and allowing mobility of the bearing surface. We reserve the description “meniscal-bearing” for implants in which the femoral condyle is spherical and the bearing can function like its analogue in nature. These design features were developed to decrease the fatigue wear associated with failure of the polyethylene in knee arthroplasty. Currently, there are few intermediate-term follow-up reports and no long-term follow-up reports, as far as we know, on the use of these devices, but almost every manufacturer of total knee-replacement components is developing a product that they hope to introduce to the market. In this Instructional Course Lecture, we explore the rationale for the use of mobile-bearing knee devices and we update the clinical follow-up of these devices. The clinical results of use of the Oxford unicompartmental replacement (Biomet, Warsaw, Indiana), the Low-Contact Stress knee replacement (LCS; DePuy, Warsaw, Indiana), and the Self-Aligning knee replacement (SAL; Sulzer, Austin, Texas) are highlighted, as these devices have been followed for at least five years.