Fixed bearing (FB) total knee replacement is a well established technique against which new techniques must be compared. Mobile bearing (MB) prostheses, in theory, reduce polyethylene wear but the literature is yet to provide evidence that they are superior in terms of function or long-term survivorship. In addition there has been no comparison of patella resurfacing on the outcome of either design. The aims of this randomised prospective study were firstly to determine whether a mobile bearing prosthesis produced better clinical outcome and range of motion at two year follow-up and secondly to assess the effect of patella resurfacing on the outcomes of both types of bearing design.
Three hundred fifty-two patients were randomised into receiving either a PFC Sigma© cruciate sacrificing total knee arthroplasty either with a mobile bearing or a fixed bearing, with a sub-randomisation to either patella resurfacing or patella retention. All patients participated with standard clinical outcome measures and had their range of motion measured both pre-operatively and at follow-up.
The mobile bearing TKR design had no impact on range of motion; Oxford Knee Score and American Knee Society knee and function scores when compared to its fixed bearing equivalent.
At two year follow-up there was no difference between the PFC Sigma© fixed and mobile bearing designs. With no clinical difference between the cohorts, we cannot recommend one design over the other. Long term benefits, particularly with regards to polyethylene wear, may yet be demonstrated. Level of evidence--1B.