O1246 IN VIVO KINEMATICS OF A POSTERIOR STABILIZED TOTAL KNEE ARTHROPLASTYWITH A FIXED OR A MOBILE BEARING COMPONENT

Abstract

Aims: This study compared in vivo kinematics of a posterior stabilized TKA inserted either with a fixed (FBC) or with a mobile bearing component (MBC). Methods: Ten patients with unilateral previously defined TKA were selected among 150 TKA performed in 2000 by a single surgeon according to the following criteria: primary TKA because of osteoarthritis, controlateral knee free of clinical symptoms, patient < 80, TKA flexion > 90°, knee IKS score > 80/100. Ten TKA (10 patients) were selected differing only by the adjunction of the mobile bearing (5 MBC and 5 FBC). The range of the 3 knee rotations (flexion, axial rotation, varus-valgus) were assessed by means of a 6-degree freedom electromagnetic goniometer during: level walking, rising from a chair, non weight-bearing flexion. Non-parametric tests compared motions between TKA and contro-lateral knee and between MBC and FBC. Results: FBC had a better mobility that MBC in valgus-varus, which was related to a larger frontal laxity. According to the increase in frontal laxity, FBC demonstrated better axial rotations that MBC in non-weight-bearing (NS). However, better ranges of axial rotation were recorded in MBC in weight-bearing (p< 0.05) (MBC axial rotation exceeded by 10° the motions of FBC). In patients with MBC, there was no difference in range of motion between the TKA and the controlateral healthy knee. In the FBC group the range of axial rotation was lower in the TKA by comparing with the controlateral knee (p< 0.05). Conclusion: With a unique prosthetic design our study suggests the role of MBC to reproduce a physiological range of axial rotation in weight-bearing. The MBC better reproduced knee kinematics Shoulder instability