Effect of gluteal muscle strengthening exercise on sagittal balance and muscle volume in adult spinal deformity following long-segment fixation surgery

This study aimed to investigate the changes in gluteal muscle volume and the effects of such changes in spinal alignment as a result of postoperative gluteal muscle strengthening exercise (GMSE) in patients following long-segment fixation for adult spinal deformity (ASD). Eighty-three consecutive patients (average age, 70.1 years) were analyzed. Three-dimensional CT scans were conducted to obtain serial axial gluteus muscle image slices. The size of each muscle area in every image slice was measured by Computer Aided Design and the sum of each muscle area was calculated. At the last follow-up, the sagittal vertical axis was significantly greater in the basic postoperative exercise group (1.49 mm vs. 17.94 mm), and the percentage of optimal sagittal alignment was significantly higher in the GMSE group (97.8% vs. 84.2%). At the last follow-up, the gluteus maximus volume was significantly higher in the GMSE group (900,107.1 cm(3) vs. 825,714.2 cm(3), p = 0.036). For the increase in muscle volume after 1 year, gluteus maximus and medius volumes showed a significant intergroup difference (+ 6.8% vs. + 2.4% and + 6.9% vs. + 3.6%). The GMSE protocol developed in this study could effectively increase gluteal muscle volume and maintain the optimal sagittal balance in patients with ASD.