Can lumbar paraspinal muscle/fat ratio and spinopelvic parameters predict short-term outcomes after decompressive surgeries in lumbar disc herniation and lumbar spinal stenosis?

Background and Objectives: We aimed to investigate whether the lumbar paraspinal muscle/fat ratio influences the outcomes of patients who had simple decompressive surgeries for lumbar disc herniation (LDH) or lumbar spinal stenosis. We also wanted to see if the spinopelvic parameters change with surgery and whether this change influences the outcomes. Materials and Methods: This was a prospective study on patients with lumbar spinal stenosis (20 patients) and LDH (20 patients) who underwent simple discectomy or decompressive surgery between November 2021 and May 2022. Visual Analog Scale (VAS) for back and leg pain, Oswestry Disability Index, and Japanese Orthopedic Association (JOA) score were performed before and 3 months after surgery. Spinopelvic parameters were measured on whole spine radiographs before and 3 months after surgery. On axial magnetic resonance images, paraspinal muscle volume and muscle/fat ratios were calculated. All data were statistically analyzed with SPSS program. Results: There was a significant improvement in VAS, Oswestry, and JOA scores after surgery. We observed that more preoperative paraspinal muscle mass was positively correlated with lumbar lordosis (LL) and negatively correlated with sagittal vertical axis (SVA), VAS leg scores, and Oswestry scores. Furthermore, we observed a positive correlation between preoperative SVA and VAS leg scores. Conclusion: Despite limited number of patients, and shorter follow-ups, this prospective study demonstrates a correlation among the lumbar paraspinal muscle/fat ratio, preoperative/postoperative spinopelvic parameters, and surgical outcomes. Increased paraspinal muscle ratio was correlated with lower SVA values and increased LL; lower VAS leg scores; higher Oswestry scores which reflects better surgical outcomes.