Prognostic impact of preoperative MRI on core decompression in ARCO stage III osteonecrosis of the femoral head: a retrospective cohort study

Abstract Background Managing ARCO stage III osteonecrosis of the femoral head (ONFH) is controversial, as surgeons choose between joint preservation and arthroplasty. While MRI provides superior assessment of lesion geometry compared with radiographs and may theoretically allow more precise targeting for debridement, it remains unclear whether preoperative MRI-based trajectory planning improves hip survival after core decompression in ARCO Stage III disease compared with pure fluoroscopic guidance. Obtaining an additional MRI solely to determine the three-dimensional location of the lesion prior to core decompression may impose financial and time burdens without adding significant value to treatment. This study aimed to determine whether the absence of timely three-dimensional imaging has an impact on the prognosis of patients with ARCO Stage III disease undergoing core decompression. Methods This study retrospectively analyzed patients with ARCO stage III ONFH who underwent core decompression between 2010 and 2023 at a single institution. The hips were categorized into MRI-guided group and X-ray-guided group based on the availability of preoperative MRI. The primary outcome was the rate of conversion total hip arthroplasty at one, two and five years. Secondary outcomes included visual analogue scale (VAS) and Harris Hip Score (HHS). Results A total of 241 hips in 207 patients were included in the analysis and were categorized into MRI-guided group (114 hips) and X-ray-guided group (127 hips). Overall survival at one, two, and five years was 70.5%, 57.3%, and 46.5%, respectively. Among stage IIIa hips, five-year survival was higher in the X-ray-guided group than in the MRI-guided group (62.8% vs. 41.9%, P = 0.036). In stage IIIb, outcomes were poor and comparable between groups (34.7% vs. 37.5%).There was no difference in conversion-free-survival between MRI-guided and X-ray-guided group at last follow-up. Postoperative VAS and HHS improved significantly in both groups, with no intergroup differences. Conclusion Preoperative MRI availability did not significantly influence survival following core decompression, THA conversion, or functional outcomes in ARCO stage III ONFH. X-ray-guided core decompression may be a feasible treatment option for stage III ONFH when radiographic diagnosis is evident, particularly in settings with limited MRI accessibility. Level of evidence Level III, retrospective cohort study.