Association between fat infiltration of paraspinal muscle, sagittal pelvic alignment and stenosis grade in patients with degenerative lumbar spinal stenosis

Introduction Sagittal balance and fatty infiltration of paraspinal muscle are important factors in patients with lumbar spinal stenosis (LSS) that may affect patients' quality of life. Sagittal spinopelvic parameters and fatty infiltration may be associated with the severity of LSS. The purpose of this study was to test the hypothesis that severity of fatty infiltration correlates with severity of LSS and with sagittal pelvic alignment independent of age. Methods Age and body mass index (BMI) were extracted. Fatty infiltration was rated according to Goutallier classification and the severity of LSS was graded according to Schizas at five intervertebral disc levels. Overall fatty infiltration was computed as average fatty infiltration (aFI) and severity of LSS was defined as the highest severity of LSS of all segments. The sagittal spinopelvic parameters pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL) and PI-LL were measured. Associations among parameters were assessed using Spearman correlation coefficients adjusted for age (α = 0.05). Results 165 LSS patients with a median age of 69 years were included. All parameters correlated with age (R>0.162, P<0.05) except BMI and LL (R 0.05). aFI correlated with PI, PT and PI-LL before (R>0.371, P 0.180, P 0.187, P<0.05) but not after (R 0.05) adjusting for age. aFI correlated with severity of LSS before (R=0.349, P 0.05) after adjusting for age. Conclusions The correlation of aFI with sagittal spinopelvic parameters indicates that there might be a relationship between muscle characteristics and the sagittal alignment. Sagittal spinopelvic parameters and fatty infiltration of paraspinal muscles are not associated with radiological severity of LSS. Whether they are associated with clinical manifestation of LSS remains to be investigated.