Comparative Survivorship of Different Tibial Designs in Primary Total Knee Arthroplasty.

BACKGROUND: Few registry-based studies in the United States have compared the survivorship of different knee implant designs in total knee arthroplasty. The purpose of this study was to compare differences in survivorship of commonly used tibial implant designs in primary total knee arthroplasty.
METHODS: A total of 16,584 primary total knee arthroplasties in 11,992 patients were performed at a single institution from 1985 to 2005. Patients were prospectively followed at regular intervals to ascertain details of subsequent revisions. Overall revision rates and revisions for aseptic loosening, wear, and osteolysis were compared across twenty-two tibial implant designs using Cox proportional hazards regression models adjusting for age, sex, calendar year, and body mass index.
RESULTS: In comparison with metal-backed modular implants, all-polyethylene tibial components had a significantly lower risk of revision (hazard ratio, 0.3; 95% confidence intervals: 0.2, 0.5 [p < 0.0001]). The risk reduction with all-polyethylene tibial components was not affected by age, sex, or body mass index. With metal-backed modular tibial designs, cruciate-retaining knees performed better than the posterior-stabilized knees (p = 0.002), but this finding was limited to one specific metal-backed modular tibial component, the Press Fit Condylar design. With all-polyethylene tibial components, there was no survivorship difference between cruciate-retaining and posterior-stabilized designs.
CONCLUSIONS: All-polyethylene tibial components were associated with better outcomes than metal-backed modular components. Cruciate-retaining and posterior-stabilized designs performed equally well, except with the Press Fit Condylar design. Obese patients may have superior results with all-polyethylene and posterior-stabilized components. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.