Correlation of psoas major muscle morphology with function and clinical symptoms in patients with symptomatic multilevel lumbar spinal stenosis

Abstract Objective This study was performed to quantify the morphological characteristics of the psoas major muscle in patients with symptomatic multilevel degenerative lumbar spinal stenosis (SMLSS) and assess the correlations of these morphological characteristics with function and clinical symptoms. Methods One hundred fourteen patients diagnosed with SMLSS (≥ 3 segments) were included. The patients’ presenting symptoms were assessed with the Oswestry Disability Index (ODI), and visual analogue scale (VAS) scores were recorded. The morphology of the psoas major was evaluated at the L3/4 intervertebral disc level in three ways: by measuring (i) the psoas muscle mass index (PMI); (ii) the mean muscle attenuation (Hounsfield units, HU); and (iii) the morphologic change of the psoas major (mean ratios of the short axis to the long axis of the bilateral psoas major). Results Men had a higher PMI than women (p = 0.001). Patients with severe disability had a significantly lower PMI (p = 0.002) and muscle attenuation (p = 0.001). The PMI and muscle attenuation were significantly higher in the patients with no or mild back pain (both p