Radiographic Progression in the Pre-Radiographic Stage of Osteonecrosis of the Femoral Head.

Abstract

Background: Early and accurate diagnosis of osteonecrosis of the femoral head (ONFH) is crucial for the success of joint-preserving treatments. Although multimodal diagnostic criteria, including radiographs, enhance diagnostic accuracy, they are limited in detecting pre-radiographic stages. Magnetic resonance imaging (MRI) is widely utilized; however, it is associated with the risk of overdiagnosis. This study aimed to characterize the pre-radiographic stage of ONFH diagnosed solely by MRI and to elucidate its progression and factors influencing it.

Methods: This retrospective study included 538 newly diagnosed Stage 1 (pre-radiographic) ONFH cases with consecutive radiographic follow-ups from the registry of a nationwide hospital-based sentinel monitoring system established by the Japanese Investigation Committee between 2010 and 2018. Demographic and clinical characteristics were analyzed, and factors influencing radiographic progression were identified.

Results: Among the Stage 1 ONFH, 90.1% of cases were diagnosed solely by MRI, with 79% potentially attributed to systemic corticosteroid administration. Of the 485 patients who have ONFH diagnosed solely by MRI, 156 hips (32.2 %) 56 hips (11.5%), eight hips (1.6%), and one hip (0.2 %) progressed to Stage 2, Stage 3A, Stage 3B, and Stage 4, respectively, over an average duration of 22.7 months. The remaining 264 hips (54.4%) showed no progression after a mean follow-up duration of 49.6 months. Sex, bilaterality, and type classification were significantly associated with the progression of ONFH, which was diagnosed solely by MRI.

Conclusion: Although MRI is essential for detecting pre-radiographic stage ONFH, less than half of pre-radiographic ONFH cases progress to Stage 2 or higher. These findings highlight the potential for overtreatment if management decisions rely solely on MRI findings.