Mode of fixation and Survivorship in Primary Total Knee Arthroplasty in the American Joint Replacement Registry

Background A recent rapid increase in cementless total knee arthroplasty (TKA) has been noted in the American Joint Replacement Registry (AJRR). The purpose of our study is to compare TKA survivorship based on the mode of fixation reported to the AJRR in the Medicare population. Methods Primary TKAs from Medicare patients submitted to AJRR from 2012 to 2022 were analyzed. The Medicare and AJRR databases were merged. Cox regression stratified by sex compared revision outcomes (all-cause, infection, mechanical loosening, and fracture) for cemented, cementless, and hybrid fixation, controlling for age and the Charlson Comorbidity Index (CCI). Results A total of 634,470 primary TKAs were analyzed. Cementless TKAs were younger (71.8 versus 73.1 years, P < 0.001) than cemented TKAs and more frequently utilized in men (8.2 versus 5.8% women, P < 0.001). Regional differences were noted, with cementless fixation more common in the Northeast (10.5%) and South (9.2%) compared to the West (4.4%) and Midwest (4.3%) (P < 0.001).No significant differences were identified in all-cause revision rates in men or women ≥ 65 for cemented, cementless, or hybrid TKA after adjusting for age and CCI. Significantly lower revision for fracture was identified for cemented compared to cementless and hybrid fixation in women ≥ 65 after adjusting for age and CCI (P = 0.0169). Conclusion No survivorship advantage for all-cause revision was noted based on mode of fixation in men or women ≥ 65 after adjusting for age and CCI. A significantly lower revision rate for fractures was noted in women ≥ 65 utilizing cemented fixation. Cementless fixation in primary TKA should be used with caution in elderly women.