Fig. 3

Spinopelvic parameters measurement and back muscle evaluation. a Measurement of spinal parameters. b Measurement of pelvic parameters. c The fascial boundary of lumbar paravertebral muscles (yellow circle): the fascia thoracolumbalis was traced down laterally and anteriorly to the dorsal side of the quadratus lumborum, followed by the posterior surface of the facet and lamina, and lateral margin of spinous process. d The boundary of vertebral body (yellow circle). Muscle/disk ratio: 16.267/17.343 = 0.94. e Cut the muscle along the fascial boundary. f Bright pixels of fat tissue in the MR images were colored in red (darker color in the black and white version) using pseudocoloring technique. The percentage of the red pixel area in the muscle compartment was the percentage of fat infiltration (29.43%)