Minimum twenty-year follow-up of fixed-vs mobile-bearing total knee arthroplasty: Double blinded randomized trial

Mobile-bearing (MB) inserts, designed to minimize aseptic loosening and to reduce contact stresses leading to polyethylene wear, are an alternative to fixed-bearing (FB) inserts. Most studies have shown no significant difference between MB and FB constructs, and there is limited long-term data comparing the two constructs [1,2,3,4]. The purpose of this study was to report the outcomes of a randomized controlled trial comparing MB versus FB inserts on patients with minimum 20-year follow-up.

Between 2002 and 2003, 132 patients were randomized intra-operatively to the rotating-platform (RP) prosthesis group or the FB prosthesis group. 40 patients from the previous minimum 12-year follow-up were evaluated to obtain information on implant survival and satisfaction. Basic univariate statistics were used.

26 patients were deceased, and 4 patients were lost to follow-up. This left 10 remaining knees (FB = 5, RP = 5) for inclusion. The mean age at surgery was 56.8 years, and the mean follow-up was 21 years overall for both groups. There were four failures and two revisions in total for each group 12. The RP revisions were for patellar component loosening and deep infections. The revisions on FB knees were for patella fracture and dislocation, pain from an oversized femoral component, and a loose tibial baseplate. The remaining patients expressed satisfaction with their replaced knees. No additional revisions were reported in this follow-up study. With the numbers available for study, there was no difference in ROM at 122° ± 12.5° for RP knees and 119° ± 6.5° for FB knees (p = 0.92).

There were few revisions, and most patients, in both RP and FB groups, expressed satisfaction and limited wear with their knees. While a safe, viable option for TKA, RP inserts did not result in long-term clinical benefit compared to FB.