The low contact stress (LCS) mobile-bearing total knee replacement (TKR) was designed to minimise polyethylene wear, aseptic loosening and osteolysis. However, registry data suggests there is a significantly greater revision rate associated.
The primary aim of this study was to assess long-term survivorship of the LCS TKR performed at a single high-volume centre. Secondary aims were to assess survival by mechanism of failure and identify predictors of revision.
During a 13-year period (1993–2006) 1091 LCS TKRs were performed by two senior surgeons. Thirty-three with incomplete data were excluded. The patients were retrospectively identified from an arthroplasty register. Mean age was 69 (range 30–96) years. Five hundred seventy-seven TKRs were performed in females, 481 in males. Mean follow-up was 14 years (SD 4.3).
There were 59 revisions during the study period: 14 (23.7%) for infection, 18 (30.5%) for instability, and 27 (45.8%) for polyethylene wear. Three hundred ninety-two patients died. All-cause survival at 10 years was 95% (95%CI 91.7–98.3) and at 15 years 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%CI 92–100). Of the 27 with polyethylene wear, only 19 (70.4%) had osteolysis requiring component revision, the other eight (29.6%) had polyethylene exchanges. Cox regression analysis identified younger age as the only predictor of revision (HR 0.96, 95%CI 0.94–0.99, p = 0.003), with a four percent decreased risk of revision for each increase in year of age.
The LCS TKR demonstrates excellent long-term survivorship with a low rate of revision for osteolysis, however this risk is increased in younger patients.