Background: Currently, the use of metal-backed tibial components is more common than the use of all-polyethylene components in total knee arthroplasty. However, the available literature indicates that all-polyethylene tibial components are not inferior to the metal-backed design. We hypothesized that there would be no difference in the ten-year survival rate between all-polyethylene and metal-backed tibial components of a specific design in a large nationwide cohort.
Methods: In the Swedish Knee Arthroplasty Register, we identified 27,733 cruciate-retaining total knee replacements using the press-fit condylar prosthesis with either metal-backed or all-polyethylene tibial components inserted from 1999 to 2011. Unadjusted survival functions were calculated with the end points of revision for any reason, revision due to infection, and revision due to reasons other than infection, and the differences between the groups were investigated with the log-rank test. Cox proportional hazard models were fitted to analyze the influence of various covariates on the adjusted relative risk of revision.
Results: The median duration of follow-up was 4.5 years (range, zero to 12.9 years). Of all total knee replacements, 16,896 (60.9%) were in women and 10,837 (39.1%) were in men. Metal-backed components were used in 16,011 total knee arthroplasties (57.7%) and all-polyethylene in 11,722 total knee arthroplasties (42.3%). With revision for any reason as the end point, the all-polyethylene tibial component had slightly superior, unadjusted ten-year survival compared with the metal-backed component: 97.2% (95% confidence interval [CI], 96.7% to 97.7%) compared with 96.6% (95% CI, 96.2% to 96.9%; p = 0.002). Cox multiple regression analysis adjusting for age group, sex, and patellar resurfacing showed that all-polyethylene components had a reduced risk of revision for any reason (relative risk = 0.75; 95% CI, 0.64 to 0.89) and a reduced risk of revision due to infection (relative risk = 0.63; 95% CI, 0.46 to 0.86). Patellar resurfacing and male sex increased the risk of revision due to infection (relative risk = 2.22 [95% CI, 1.37 to 3.62] and 2.21 [95% CI, 1.66 to 2.94], respectively).
Conclusions: These all-polyethylene tibial components were at least as good as or superior to metal-backed tibial components with respect to implant survivorship at ten years in cruciate-retaining total knee replacements. We concluded that these less expensive all-polyethylene tibial components can be safely and effectively used in total knee arthroplasty.
Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
1Department of Orthopedics, Institute of Surgical Sciences, Uppsala University Hospital, SE-751 85, Uppsala, Sweden. E-mail address: firstname.lastname@example.org
2The Swedish Knee Arthroplasty Register, Department of Orthopedics and Clinical Sciences, Lund University, SE-221 85, Lund, Sweden