Primary total knee arthroplasty for primary and secondary osteonecrosis

Aims: Total knee arthroplasty (TKA) for end-stage osteonecrosis has historically been associated with concerns regarding aseptic loosening, and long-term data are limited. The purpose of this study was to update and expand our previous series with long-term follow-up, with specific emphasis on implant survivorship, risk factors for failure, complications, and clinical outcomes in a consecutive cohort of TKAs performed for primary and secondary osteonecrosis. Methods: We retrospectively identified 295 consecutive TKAs in 266 patients for osteonecrosis performed at a single tertiary care academic institution from January 2002 to July 2022. Of these, 207 TKAs (70%) were performed for primary osteonecrosis, and 88 (30%) for secondary osteonecrosis. The predominant cause of secondary osteonecrosis was steroid use (59%; n = 52), followed by post-traumatic (25%; n = 22), radiation-induced (9%; n = 8), and alcohol-induced (7%; n = 6) osteonecrosis. Implant survivorship was analyzed as a time-to-event outcome using Kaplan-Meier estimation. The mean age was 61 years (18 to 93), with 67% being female (n = 197). The mean follow-up was nine years (2 to 20). Results: The 15-year survivorship free of any revision for the entire cohort was 92% (95% CI 87 to 97), with similar rates between primary and secondary osteonecrosis (92% (95% CI 87 to 98) vs 93% (95% CI 87 to 100), respectively; p = 0.459). Varus-valgus constraint implant designs (HR 10.8 (95% CI 2.7 to 43.4); p < 0.001) and tibial stem use (HR 12.0 (95% CI 4.1 to 35.1); p < 0.001) were associated with an increased risk of any revision. The 15-year survivorship free of aseptic loosening was 97% (95% CI 93 to 100) for the entire cohort. Age under 65 years (HR 2.7 (95% CI 1.4 to 5.4); p = 0.005) and secondary osteonecrosis (HR 1.9 (95% CI 1.0 to 3.4); p = 0.044) were associated with an increased risk of any reoperation at 15 years. Conclusion: TKA is a durable and reliable option for primary osteonecrosis at long-term follow-up. However, TKAs performed for secondary osteonecrosis carry a higher reoperation risk.