Abstract
The Low Contact Stress (LCS) mobile-bearing total knee replacement (TKR) was designed to minimize polyethylene wear, aseptic loosening and osteolysis. However, registry data suggests there is a significantly greater revision rate associated with the LCS TKR.
The primary aim of this study was to assess long-term survivorship of the LCS implant. Secondary aims were to assess survival according to mechanism of failure and identify predictors of revision.
We retrospectively identified 1091 LCS TKRs that were performed between 1993 and 2006. There was incomplete data available 33 who were excluded. The mean age of the cohort was 69 (SD 9.2) years and there were 577 TKRs performed in females and 481 in males. Mean follow up was 14 years (SD 4.3).
There were 59 revisions during the study period: 14 for infection, 18 for instability, and 27 for polyethylene wear. 392 patients died during follow up. All cause survival at 10-year was 95% (95%CI 91.7–98.3) and at 15-year was 93% (95%CI 88.6–97.8). Survival at 10-years according to mechanism of failure was: infection 99% (95%CI 94–100%), instability 98% (95%CI 94–100%), and polyethylene wear 98% (95%CI92–100). Of the 27 with polyethylene wear only 19 had associated osteolysis requiring component revision, the other 8 had simple polyethylene exchanges. Cox regression analysis, adjusting for confounding variables, identified younger age was the only predictor of revision (hazard ratio 0.96, 95%CI 0.94–0.99, p=0.003).
The LCS TKR demonstrates excellent long-term survivorship with a low rate of revision for osteolysis, however the risk is increased in younger patients.
