Introduction: Mobile bearing total knee arthroplasty (TKA) has been developed to theoretically provide better, more physiological function of the knee and produce less PE wear. The theoretical superiority of mobile bearing TKAs over fixed bearing devices has not yet been proven in clinical studies. The objective of the present study was to prospectively analyze clinical and functional outcomes of randomized fixed and mobile bearing total knee arthroplasty patients by means of gait analysis, electromyography and established clinical scores.
Methods: In a prospective, randomized, patient- and observer-blinded, clinical study, 33 patients (mean age 63 years) received a cruciate retaining Genesis II TKA for primary osteoarthritis. 16 patients received a mobile bearing and 17 patients a fixed bearing device. The day before surgery and 24 months postoperatively, established clinical (KSS, HSS, WOMAC, UCLA, VAS) and quality of life (SF-36) scores were used to compare both patient groups. Electromyography of standardized locations was measured with the MyoSystem 2000 and analyzed with Myoresearch software. Gait analysis was performed with a six camera motion analysis system and force platforms.
Results: Both groups showed significant improvements between pre- and postoperative evaluation in gait analysis and electromyography, but gait analysis results as well electromyography did not show any difference between both groups at follow-up. Clinical and quality of life results significantly improved from pre- to postoperative evaluation, but only the Knee Society Score showed a significant superiority of the mobile bearing group (mean 159.0; SD 27.7; range, 105–196) over the fixed bearing group (mean 134.4; SD 41; range, 56–198) (p=0.0022).
Conclusions: In the present study, no functional advantage of mobile bearing TKA over fixed bearing devices could be found, although the mobile bearing group had better clinical results. Thus, long-term clinical results and in-vivo wear analyses have to be followed, and more subtle functional analyses (e.g. fluoroscopy) have to be employed to finally judge over the theoretical advantage of mobile bearing TKAs.
