Is There a Need for a Central Stem within the Keel of Primary Tibial Baseplates in Total Knee Arthroplasty

Abstract Clinical studies suggest a role for the keel of the tibial component in preventing aseptic loosening in total knee arthroplasty (TKA). To analyze the role of a central stem within the keel, we compared two designs of tibial components for the Triathlon TKA (Stryker): standard keel components that have a central stem and fins (Triathlon universal tibial baseplate) and finned components that have fins alone and lack a central stem (Triathlon primary tibial baseplate). Questions: (1) is there a difference in all-cause revision rate or revision rates for loosening? (2) Is there a difference in revision rates when stratified by sex, body mass index (BMI) or insert conformity? We used retrospective data from the Australian Orthopaedic Association National Joint Replacement Registry of 76,710 minimally stabilized cemented TKAs performed without stem extensions for primary osteoarthritis from September 1999 to December 2023. The mean age of patients was 69.3 ± 8.9 years, and 59.6% were females. The mean follow-up was 5.6 years. Cumulative percent revision from Kaplan–Meier estimates was used to compare the revision rates between finned and standard keel tibial components. Hazard ratios (HR), adjusted for sex and age, were used for comparison. There was no difference in the overall revision rate between standard and finned tibial components (HR: 1.05, 95% confidence interval [CI]: 0.74–1.48, p = 0.779) or in revision rates for loosening with the numbers available for the study. Stratification by sex, BMI, and insert conformity (cruciate-retaining and condylar-stabilizing) did not show a difference between the groups. Females had a marginally higher risk of revision than males when finned components were used (HR: 1.33, 95% CI: 1.01–1.75, p = 0.045). Central stems within the keel of cemented tibial components do not alter the survivorship of minimally stabilized TKA.