Correlation analysis between morphological changes of lumbar core muscles and stages of femoral head necrosis

To semi-quantitatively assess the morphological changes (cross-sectional area and fat infiltration) of lumbar core muscles in ONFH patients at different ARCO stages using MRI, and to explore their correlation with disease staging. A total of 90 ONFH patients diagnosed between March 2019 and March 2025 were included and divided into three groups according to ARCO stage: stage II, III, and IV, with 30 patients in each group. Additionally, 30 healthy volunteers were enrolled as a control group. All participants underwent lumbosacral 3.0T MRI examination. The CSA and FI rate of bilateral multifidus (MF) and erector spinae (ES) muscles were measured on axial images at the L4/L5 intervertebral disc level. One-way analysis of variance (ANOVA) with post-hoc pairwise comparisons was used to analyze differences between groups, and Spearman correlation analysis was employed to evaluate the relationship between muscle parameters and ARCO stage. Compared with the control group, the CSA of the contralateral (opposite side of the necrotic hip) MF and ES muscles significantly decreased, while the FI rate significantly increased with increasing ARCO stage. In the same ONFH patient, the CSA of the ipsilateral (same side as the necrotic hip) MF and ES muscles was significantly larger than that of the contralateral side, and the FI rate was significantly lower than that of the contralateral side (all P < 0.05). There were no statistically significant differences in CSA or FI rate of the ipsilateral muscles among the different ARCO stage groups (P > 0.05). Spearman correlation analysis showed that ARCO stage was negatively correlated with the CSA of the contralateral MF (r =-0.568) and ES (r =-0.819) muscles (both P < 0.01), and positively correlated with the FI rate of the contralateral MF (r = 0.895) and ES (r = 0.803) muscles (both P < 0.01). Atrophy and fat infiltration of the contralateral lumbar core muscles in ONFH patients are correlated with disease severity. These findings may be related to compensatory and adaptive mechanisms within the lumbopelvic-hip kinetic chain. Imaging assessment of core muscles may provide an important reference for comprehensive management and rehabilitation intervention in ONFH.