The effects of rotation on radiological parameters in the spine.

Background Vertebral rotation in straight spines or in spines with small scoliosis may potentially affect measurement of radiological parameters in both the frontal and sagittal plane. This is important, since it could lead to potential misdiagnosis of scoliosis and other clinical consequences, and until now, this has not been examined. Purpose To examine the effect of axial vertebral rotation of the spine on measurement of common radiological parameters. Material and Methods Reconstructions from computed tomography scans of 40 consecutive included and anonymized patients with straight spines or small scoliosis. Fourteen sagittal and coronal reconstructions covering the whole pelvis and spine were executed. Radiographic parameters in both the frontal and sagittal plane were measured blinded and separately by three doctors. These parameters were evaluated for inter-rater reliability using intraclass correlation coefficient and mixed model analysis for the effects of rotation. The parameters were also analyzed sub-stratified according to "Lenke's classification" and 15 sub-categories of thoracic and lumbar Cobb's angle (CA). Results Vertebral rotation in general does not have any significant effects in both the frontal and sagittal plane. However, there are significant effects on CA and spinopelvic radiologic parameters in extreme rotation or for larger scoliosis. Inter-rater reliability was very good to good. Conclusion In conclusion, axial spinal rotation does not influence common radiological parameters in the frontal and sagittal plane, except in cases of extreme rotation or large scoliosis for selected parameters; thus, this does not lead to potential misinterpretation in scoliosis diagnosis, treatment, or research.