Influence of joint area design on tibial component migration: comparison among a fixed symmetrical, asymmetrical, and moveable bearing.

Abstract

Fifty-four knees (50 patients) were allocated to three different tibial polyethylene inserts (standard/rotating platform/FS1000) in the Freeman-Samuelson (Finsbury Orthopaedics Ltd, Surrey, United Kingdom) total knee arthroplasty. The FS1000 design has a spherical medial and a roller-in-trough configuration laterally. Radiostereometric examinations were done postoperatively and after 3, 12, and 24 months. The median migration of the metal-backing and the Hospital for Special Surgery scores did not differ between the three groups. At 2 years, the median external/ internal displacements for the rotating platforms were 2.8 degrees and 0.2 degrees, respectively (rotating platforms versus standard inserts/rotating platforms versus FS1000: P < .0005). Longitudinal rotations above the detection limits for radiostereometry were observed in some of the fixed implants (standard and FS1000 designs), indicating conditions for backside wear.