Purpose: The objective was to analyze the role of the thoracolumbar sagittal flexibility on the outcome after posterior spinal fusion of Lenke 1 and 2 adolescent idiopathic scoliosis with last touched vertebra as the lowest instrumented vertebra.
Methods: We included 105 thoracic AIS patients who had a posterior spinal fusion with a 2 years minimum follow-up. Thoracolumbar junction flexibility was assessed on dynamic sagittal X-rays and compared to the standing position. Adding-on was defined according to radiographic Wang criteria. The junction was considered flexible if the variability from the static position to flexion and/or extension was greater than 10°.
Results: Mean age of the patients was 14 ± 2 years. The preoperative mean Cobb angle was 61 ± 12.7° and 27.5 ± 7.7° after surgery. Mean follow-up was 3.1 years. Twenty-nine patients (28%) developed an adding-on. Thoracolumbar junction range of motion was higher (p = 0.017) with higher flexibility in flexion (p < 0.001) in the no adding-on group. In no adding-on group, 53 patients (70%) had a flexible thoracolumbar junction, and 23 patients (30%) had a stiff thoracolumbar junction in flexion and flexible in extension. In adding-on group, 27 patients (93%) had a stiff thoracolumbar junction, and 2 patients (7%) had a flexible junction in flexion and stiff in extension.
Conclusion: The flexibility of the thoracolumbar junction is a determining factor in the surgical outcome after posterior spinal fusion for AIS and should be considered in correlation with the frontal and sagittal alignment of the spine.
Keywords: Adolescent idiopathic scoliosis; Bending films; Lowest instrumented vertebra selection; Thoracolumbar junction flexibility.
© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.