Clinical results of the Oxford knee. Surface arthroplasty of the tibiofemoral joint with a meniscal bearing prosthesis.

The Oxford method of knee arthroplasty replaces the femoral condyles with convex spherical metal components and relines the tibial plateaus with flat metal components. Free meniscal bearings of polyethylene, spherically concave above and flat below, lie between the fixed metal components, held in place by their geometry and ligamentous tension. Advantages of the design include: congruity of the articulating surfaces; unconstrained tibiofemoral movement; preservation of all the ligaments with facility to tension them accurately from a range of bearing thicknesses; minimal bone excision; applicability to unicondylar use. Laboratory studies showed that combined rolling and sliding at meniscofemoral and meniscotibial interfaces mimic normal joint kinematics and mechanics. One hundred twenty-five bicompartmental implants were followed for two to six years. Pain was relieved in 90%; mean flexion limit was 99 degrees and mean flexion deformity 7 degrees. Stability and alignment were recovered in nearly all joints. Six knees failed and were successfully arthrodesed (two) or converted to another prosthesis (four). Eight knees required revision to replace a dislocated bearing (five) or to recement a loose component (three). In knees with an intact anterior cruciate ligament, there were no failures and a low revision rate (4.8%). The prosthesis is proposed as a reliable and safe alternative to more invasive prostheses in rheumatoid and osteoarthritic joints in which the disease is still limited to the articular surfaces.