Primary Cemented Total Knee Arthroplasty With Fully Cemented Short-Stemmed Tibial Components Is Not Associated With Reduced Five-Year Survival.

BACKGROUND

Emerging evidence suggests revision for early aseptic loosening following total knee arthroplasty (TKA) is associated with both short, native tibial stem (TS) design and morbid obesity (body mass index ≥ 40). The use of short, fully cemented stem extensions has been suggested to mitigate this risk.

METHODS

A retrospective review was performed of patients undergoing primary TKA at a single, large academic center between August 2015 and December 2022. Cohorts were created based on the presence (stemmed tibia (ST)) or absence (nonstemmed tibia (NST)) of a fully cemented short TS extension. Cox proportional hazards models were used to assess implant survival across all follow-up periods. A total of 3,930 patients were included (NST = 3,757, ST = 173). The mean time to final follow-up was 5.8 years for the NST cohort and 4.6 years for the ST cohort (P < 0.001).

RESULTS

All-cause revision occurred in 0.98% (n = 37) of the NST cohort at a mean time of 25 months. There was one revision (0.58%) in the ST cohort. Aseptic loosening occurred in two patients (0.05%), both in the NST cohort, at an average of 65 months. Morbid obesity (hazard ratio (HR) = 4.04, 95% confidence interval (CI): 1.75 to 8.60), age (HR = 0.96, 95% CI: 0.92 to 0.99), and being a man (HR = 2.05, 95% CI: 1.08 to 3.97) were significant predictors of all-cause revision, while TS extension (HR = 0.56, 95% CI: 0.06 to 2.20) was not.

CONCLUSIONS

This study did not find short, native TS design to be associated with early tibial aseptic loosening nor increased all-cause revision following primary TKA. Morbid obesity, younger age, and being a man were associated with greater risk of revision, regardless of stem extension at five years.