Mobile bearing and fixed bearing total knee arthroplasty

Abstract

The mobile bearing (MB) concept in total knee arthroplasty (TKA) was developed as an alternative to fixed bearing (FB) implants in order to reduce wear and improve range of motion (ROM), especially focused on younger patients. Unfortunately, its theoretical advantages are still controversial. In this paper we exhibit a review of the more recent literature available comparing FB and MB designs in biomechanical and clinical aspects, including observational studies, clinical trials, national and international registries analyses, randomized controlled trials, meta-analyses and Cochrane reviews. Except for some minor aspects, none of the studies published so far has reported a significant improvement related to MBs regarding patient satisfaction, clinical, functional and radiological outcome or medium and long-term survivorship. Thus the presumed superiority of MBs over FBs appears largely inconsistent. The routine use of MB is not currently supported by adequate evidences; implant choice should be therefore made on the basis of other factors, including cost and surgeon experience.

Keywords: Clinical results; fixed bearing (FB); knee joint; mobile bearing (MB); total knee arthroplasty (TKA).

Figure 1

Fixed bearing primary total knee replacement.

Figure 2

Mobile bearing, rotating platform, primary total knee replacement (A); atraumatic dislocation of the insert at 2 years post-surgery in the same patient (B).

Figure 3

Mobile bearing, rotating platform, primary total knee replacement (A); insert failure due to breakage of the retaining socket at 4 years post-surgery in the same patient (B).