Sagittal spinopelvic alignment in adolescent thoracic scoliosis secondary to Chiari I malformation: a comparison between the left and the right curves.

PURPOSE: To investigate whether the sagittal morphology differs between the left and right thoracic curves in patients with Chiari malformation-associated scoliosis (CMS).
METHODS: Thirty-four patients with a left thoracic curve constituted the CM-L group, whereas 44 patients with a right thoracic curve were assigned into the CM-R group. Another cohort of 90 age- and gender-matched asymptomatic adolescents was enrolled to serve as the control group. Seven sagittal parameters were evaluated on standing lateral radiographs, including thoracic kyphosis (TK), lumbar lordosis (LL), thoracolumbar junctional kyphosis (TJK), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS).
RESULTS: Compared to the normal controls, the TK, LL and SS were significantly greater in the CM-L group, along with a significantly decreased PT. Similar changes in SS and PT were also demonstrated in the CM-R group, while the TK and LL were found to be relatively normal compared with the control group. Concerning CMS patients with different curve directions, significantly increased TK and LL were observed in the CM-L group, whereas all three pelvic parameters were similar for the two groups. In addition, no significant differences were noted between the three groups in PI, TJK or SVA. Moreover, the LL was strongly related to the TK and SS in all three groups, but to the PI only in the control and CM-R groups. A significant correlation was also noted between TK and SS in the CM-L group.
CONCLUSIONS: Significant differences in sagittal profiles indeed exist between CMS patients and healthy adolescents, as well as between CMS patients with different curve directions. In CMI patients with a left thoracic curve, compensatory alterations appear to occur in LL in response to the increased TK to maintain a balanced posture.