Abstract
Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL® (mobile bearing) versus the AMK® and Genesis II® (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System).
The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL®, Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK®, Depuy and Genesis II®, Smith and Nephew).
Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.
No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two year follow up, and one patient was revised for infection at 6 months leaving eighty-seven patients at an average follow-up of 3.37 years (range 2.91 – 4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL - 167, AMK – 158, GenesisII – 166). There were no differences in knee flexion at two years (SAL – 117°, AMK – 115°, GenesisII – 118°).
No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.
In this prospective randomized clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.
Funding: London Health Sciences Centre Internal Research Fund
Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada
