Background: Patients who have osteonecrosis (ON) of the femoral head often require total hip arthroplasty (THA), usually before the age of 50 years. The ON population appears to have inferior outcomes compared to patients who have received THA for other conditions. The aim of this study was: (1) to compare the overall survival rate; and (2) to evaluate five- and 10-year clinical outcomes of primary THA in patients under 50 years of age who had ON or osteoarthritis (OA) using the Geneva Arthroplasty Registry. Also, we tried to identify risk factors for THA failure in patients under 50 years of age.

Methods: Patients under 50 years of age who underwent primary THA for ON or OA between 1996 and 2021 were identified. After matching the two groups by propensity score, 290 patients were finally included: 145 in each group. The mean age of the population was 43 years (range, 19 to 49), 28.3% (82 of 290) of the patients were women, and the mean body mass index was 26.3 (range, 16.7 to 46.0).

Results: The overall survival rate in the OA group was 79.8% [71.0 to 89.8] and 83.4% [76.0 to 91.6] in the ONA group, without significant difference (P = 0.68) at 20 years. Regarding clinical outcomes, we observed a difference for the pre-post delta of the pain subscale of the Harris hip score, which was higher in the OA compared to the ONA group (25.6 ± 11.6 versus 18.7 ± 14.1, P = 0.01) at 5 years postoperative. At 10 years, the pre-post delta of the Short-Form 12 physical score was higher in the OA group compared to the ON (13.9 ± 11.4 versus 5.3 ± 11.3), P = 0.05. Being older (hazard ratio = 0.92 [0.87 to 0.97], P < 0.01) or using a cementless cup (hazard ratio = 0.20 [0.05 to 0.87], P = 0.03) were identified as protective factors in the multivariate analyses.

Conclusions: In terms of survival, it's reasonable to propose a THA to patients under 50 years of age suffering from ON, which will improve their quality of life and function in the long term.

Level of evidence: Level III, Case-Control Studies.