Study design: A radiographic and clinical study.
Objective: To compare the anatomic deviation between the central hip vertical axis (CHVA) and central sacral vertical line (CSVL) in 2 distinct adolescent idiopathic scoliosis (AIS) groups (right thoracic vs. left thoracolumbar/lumbar) and normal adolescents.
Summary of background data: The CSVL was traditionally used as a reference line to assess spinal deformity. Recently, the Scoliosis Research Society 3-dimensional (3D) committee proposed the CHVA as a reference line for the 3D evaluation of scoliosis. However, a previous study showed that the CHVA was on an average 3.2 mm to the right compared with the CSVL in right thoracic AIS patients, generating a shift in evaluation of the coronal plane measurements.
Methods: Fifty-five AIS girls with right thoracic curves (TC) and 56 AIS girls with left thoracolumbar/lumbar curves (TLC) were recruited. AIS girls who had a Cobb angle >40 degrees were excluded from this study in consideration of the potential pelvic rotation in patients with large curves. Another 57 normal girls were set to be the control group. All girls were between 10 and 18 years old. The deviation between the CHVA and CSVL was measured on each posteroanterior radiograph and compared between the 3 groups.
Results: The shift of CHVA relative to CSVL was found to be significantly greater in the TC and TLC groups (2.2±3.3 mm vs. 2.3±4.0 mm, respectively) when compared with the control group (0.1±2.6 mm), but had no statistical difference between the 2 AIS groups. No significant correlations were found between age, Cobb angle, and the CHVA shift in the 3 groups. The CHVA was more commonly found to be at the right side of the CSVL in the TC (50.9%) and TLC (51.8%) groups, whereas superposition of the 2 lines was more commonly found in the control group (52.6%).
Conclusions: Anatomic deviation between the CHVA and CSVL was significantly different in the TC and TLC groups when compared with the control group, but was similar between the 2 AIS groups. The CHVA was on an average approximately 2 mm to the right when compared with the CSVL in AIS girls. Adaption of the measures related to the CSVL is necessary to adopt the CHVA as a reference axis for the 3D evaluation of idiopathic scoliosis.