Outcomes After Contemporary Cementless versus Cemented Primary Total Knee Arthroplasty at Five-Years: Some Subtle Differences.

Introduction: Cementless total knee arthroplasty (TKA) has regained interest due to the potential long-term survivorship and ease of use. However, data on contemporary cementless TKA remain limited. We investigated implant survivorship and outcomes following contemporary cementless versus cemented TKA.

Methods: We identified 3,763 primary TKAs for osteoarthritis from January 1, 2016, to December 31, 2023, using our institutional total joint registry. There were 598 cementless and 3,165 cemented TKAs. Cementless tibial components included porous titanium (Ti) in 509 knees and beaded cobalt-chromium (CoCr) in 89. We excluded all-polyethylene tibias, stemmed tibias, and revision constructs. The mean age was 68 years (range, 28 to 96), the mean body mass index was 32 (range, 17 to 65), and 56% were women. The cementless group was younger and contained more men (P < 0.05). Kaplan-Meier and Cox regression analyses adjusted for age, sex, BMI, and surgical year were performed. The mean follow-up was three years (range, two to eight).

Results: There were 61 revisions (1.6%): 11 (1.8%) in the cementless and 50 (1.6%) in the cemented group. Revisions were primarily for infection (N = 31) and aseptic loosening (N = nine). All four loosening cases after cementless TKA involved CoCr tibias within one year. All five cemented TKA loosening cases occurred between two and five years. The five-year revision-free survivorship was 92% in cementless and 97% in cemented TKAs (hazard ratio (HR) = 3; P < 0.05). Excluding CoCr tibias, Ti cementless survivorship was 97%. The five-year survivorships free from revision for infection were 98% in cementless and 99% in cemented TKAs (HR = 3; P < 0.05). There were no differences in periprosthetic fracture risk observed (P = 0.5).

Conclusions: We identified subtle differences between contemporary cementless and cemented primary TKA mid-term outcomes. We found a slightly higher infection risk in the cementless group, excellent durability of Ti cementless and cemented tibias, and a higher loosening risk with CoCr cementless tibias.