Aim:Vertebral body tethering(VBT) and posterior spinal fusion (PSF) are surgical interventions used in treatment of adolescent idiopathic scoliosis(AIS). A combined approach, particularly beneficial for patients with double curves, involves PSF targeting the thoracic curve and VBT addressing the lumbar curve. This combined procedure aims to optimize thoracic curve correction while theoretically preserving lumbar spine mobility. This study aimed to investigate lumbar motion and muscle change following hybrid surgery.Material and Methods:We conducted a prospective study including 16 patients (14 female, 2 male) who underwent either hybrid surgery or selective thoracic fusion surgery(STF) for AIS. Trunk extensor and flexor muscle strength and endurance were assessed using an isokinetic dynamometer. Range of motion (ROM) of the lumbar region was measured by a dual inclinometer. Muscle mass was calculated by evaluating the bilateral multifidus, erector spinae, and psoas muscles in the T2A axial sections at the L2 and L5 vertebral corpus plateau superior in the images taken through magnetic resonance imaging. The degree of fatty degeneration was assessed by the Goutallier classification.Results:The hybrid group comprised eight female patients with a mean surgical age of 14±1.7 years and a mean follow-up time of 16.4±8.8 months. The STF group included eight patients (six females, two males) with a mean surgical age of 14.6±1.8 and a mean follow-up time of 29.5±15.4 months were included. No significant difference was observed between the lumbar ROM, trunk flexion– extension strength, and endurance (P>0.05) of both groups. Similarly, no significant difference was observed between the paraspinal muscle cross-sectional area and the degrees of fatty degeneration in the patient’s preoperative and last follow-up. Moreover, no differences were observed in the overall Scoliosis Research Society-22 scores between the two groups (P=0.442).Conclusion:These preliminary findings show that hybrid surgery preserves lumbar motion and does not cause iatrogenic damage to the paraspinal muscles, including the psoas major.