The Relationship Between Apical Vertebral Rotation and Truncal Rotation in Adolescent Idiopathic Scoliosis Using 3D Reconstructions

Abstract

Study DesignRetrospective review of prospective data. ObjectivesTo evaluate the relationship between absolute apical vertebral rotation (AVR) evaluated with upright 3D imaging and angle of trunk rotation (ATR) before and after surgery for thoracic and lumbar curves in adolescent idiopathic scoliosis (AIS). Summary of Background DataNew imaging technology allows for improved radiographic assessment of the degree of AVR pre- and postoperatively through 3D spine models created from biplanar, simultaneous spine radiographs. MethodsA prospective registry was queried and identified 55 AIS patients with major thoracic or major thoracolumbar/lumbar curves who underwent posterior spinal fusion. All patients had biplanar upright imaging of their spine and ATR measurements assessed via scoliometer pre- and postoperatively. ResultsThere were 33 major thoracic and 22 major lumbar curves. The mean Cobb angles for thoracic and thoracolumbar/lumbar curves were 54° ± 10° and 47° ± 8° preoperatively, and 11 ± 6° and 12 ± 7° postoperatively. The differences in the mean preoperative ATR measurements for both major curve types was not statistically significant; however, the difference in AVR between thoracic curves (13 ± 6°) and lumbar curves (22 ± 7°) was significant (p < .001). There was a significant decrease in the ATR and AVR for both thoracic and thoracolumbar/lumbar curves (p < .001) postoperatively. A significant correlation between ATR and AVR was found only for the major thoracolumbar/lumbar curves (p < .001). The relationship between ATR and AVR changes for both curves was not statistically significant. ConclusionATR measured via scoliometer strongly correlates with 3D measurements of AVR in both thoracic and lumbar curves before and after surgery for AIS. No significant relationship was found between the changes in ATR and AVR due to surgery. Postoperatively, greater clinical rotational deformity remains in the thoracic spine compared to the lumbar spine, despite greater apical vertebra axial plane correction in thoracic curves. Level of EvidenceLevel II, diagnostic.