Impact of Preoperative Non‐Collapse and Collapse Durations on Total Hip Arthroplasty Outcomes in Nontraumatic Osteonecrosis of the Femoral Head

BACKGROUND: Current clinical strategies emphasize delaying total hip arthroplasty (THA) in patients with nontraumatic osteonecrosis of the femoral head (NONFH). However, it remains unknown whether prolonged abnormal joint mechanics during this delayed period compromise the final surgical outcomes. Consequently, the impact of the prolonged collapsed or non-collapsed hip joint stages on THA efficacy has not yet been evaluated. This study aimed to analyze the effect of the duration of a collapsed or non-collapsed hip joint on the efficacy of subsequent THA. METHODS: This retrospective cohort study included 111 NONFH patients who underwent primary unilateral THA between June 2022 and June 2023. Patients were grouped based on the duration of their non-collapsed or collapsed stages (≤ 1 year, 1-3 years, and > 3 years) prior to surgery. Postoperative outcome measures, including the numerical rating scale (NRS) for pain and the Harris Hip Score (HHS) for hip function, were obtained through video-call follow-up. Statistical analyses included ANOVA, Kruskal-Wallis H tests, multivariable GLM, and ROC curve analysis. RESULTS: A total of 111 patients were ultimately included in this study. Significant differences were found between the Joint Surface Non-Collapse Group and the Survival with Collapse Group regarding whether they had received oral medication treatment (p < 0.05). Patients with different survival durations of collapse demonstrated significant differences in ARCO staging at the time of final THA (p < 0.05). Postoperatively, significant differences in NRS scores were observed among patients with different survival durations of collapse (p < 0.05), with the 1-3 year collapse group reporting higher pain scores compared to the > 3 year group. However, multivariable GLM revealed that preoperative duration did not independently predict the final absolute HHS (p > 0.05), indicating an equalizing trend of THA across all groups. Notably, the duration of collapse independently predicted postoperative pain, with the 1-3 year group exhibiting significantly worse NRS scores (p = 0.023). CONCLUSION: While THA provides highly effective and equalized functional recovery regardless of the preoperative duration of the collapsed or non-collapsed stages, surgical timing significantly impacts postoperative pain. Operating during the 1-3 year post-collapse window is an independent risk factor for inferior pain relief. Given the limited subgroup sizes, these exploratory findings warrant further multicenter validation. LEVEL OF EVIDENCE: Level III.