Abstract
BACKGROUND: To compare the effect of the thoracolumbar junction angle (TLJ) on postoperative changes in both sagittal spinal and spinopelvic parameters in patients with Lenke type 1 adolescent idiopathic scoliosis (AIS) undergoing selective fusion surgery. METHODS: We retrospectively reviewed 42 patients with Lenke 1 AIS who were younger than 18 years of age and underwent posterior selective fusion in our center between 2010 and 2020. Pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), TLJ, cervical lordosis (CL), and sagittal vertical axis were evaluated using the Surgimap (https://www.surgimap.com/) measurement system. Patients were divided into 2 groups: kyphotic and lordotic TLJ. RESULTS: Of the 42 AIS patients, 25 (60%) had kyphotic and 17 (40%) had lordotic TLJ alignment. Both groups had a median follow-up of 10 years. In the TLJ kyphotic group, PT was lower in the preoperative, immediate postoperative, and final follow-up examinations compared to the TLJ lordotic group, while TK was higher compared to the TLJ lordotic group (p < 0.05). PI was significantly lower immediately postoperatively, while no statistically significant difference was observed preoperatively and at final follow-up. When all cases were evaluated, a statistically significant difference was found between preoperative, immediate postoperative, and final follow-up SS measurements (p = 0.009). TK and LL were significantly decreased in both groups. While CL was significantly higher in the TLJ kyphotic group in the preoperative and immediate postoperative periods, no statistically significant difference was found at the final follow-up (p > 0.05). Although the CL decreased in the kyphotic group, it remained within the lordotic alignment. CONCLUSIONS: The fact that the PI and PT values of patients with thoracolumbar junction kyphotic were lower than those of the TLJ lordotic group should suggest that patients may have less compensatory abilities in sagittal alignment in advanced ages, and surgeons should consider this situation when applying spinal fusion. In addition, it was observed that the cervical spine in TLJ lordotic patients was prone to kyphosis to provide sagittal alignment.