Atrophy and Fat Infiltration of Contralateral Lumbar M uscles Correlate with the Severity of Osteonecrosis of the Femoral Head

Abstract Objective :To investigate the correlation between the cross-sectional area and fat infiltration degree of the multifidus muscle in the lumbar core muscle group and the ARCO staging of femoral head necrosis. Methods :Ninety patients with ONFH diagnosed between March 2019 and March 2025 were included and divided into Stage II, Stage III, and Stage IV groups according to ARCO staging, with 30 patients in each group. Additionally, 30 healthy volunteers were included as a control group. All subjects underwent lumbosacral 3.0T MRI examination. The cross-sectional area and fat infiltration rate of the bilateral multifidus (MF) and erector spinae (LT) muscles were measured on axial images at the L4/L5 intervertebral disc level. One-way ANOVA was used to compare differences between groups, and Spearman correlation analysis was used to assess the relationship between muscle indicators and ARCO staging. Results : Compared with the control group, the cross-sectional area of the MF and LT on the healthy side in ONFH patients significantly decreased with increasing ARCO stage, while the fat infiltration rate significantly increased. In the same ONFH patient, the cross-sectional area of the multifidus and erector spinae muscles on the affected side was significantly larger than that on the healthy side, and the fat infiltration rate was significantly lower than that on the healthy side. Spearman correlation analysis showed that ARCO staging was negatively correlated with the cross-sectional area of the MF and LT on the healthy side and positively correlated with the fat infiltration rate on the healthy side. Conclusion :Atrophy and fat infiltration of the core muscles on the healthy side of the lower back are significantly correlated with the severity of ONFH. This indicates that the pathological changes in ONFH patients are not limited to the hip joint but also involve alterations in lumbopelvic compensation mechanisms, providing imaging evidence for the assessment of core muscles and rehabilitation intervention.