Correlation between the cervical sagittal alignment and spine - pelvic sagittal alignment in asymptomatic adults

BACKGROUND: Although there are studies that adequately document the linear correlation between pelvic incidence (PI), sacral slope, lumbar lordosis, and thoracic kyphosis, few have analyzed the pelvic-spine correlation including the cervical spine. METHODS: This is a cross-sectional study, wherein the cervical spine was evaluated using radiography and computed tomography (CT) scans, the lumbosacral spine and the pelvis was evaluated using radiography, in adult patients without spinal pathology. Using the Surgimap tool, cervical and spinopelvic parameters were calculated by several investigators. To evaluate the correlation between cervical and spinopelvic parameters, Spearman's coefficient was calculated. To evaluate the concordance correlation of the measured parameters of cervical sagittal alignment on tomography and conventional radiography, Lin's coefficient was calculated and Bland–Altman plots were performed. RESULTS: A total of 51 healthy adults were included in a follow-up from January 2019 to December 2020. Cervical sagittal alignment and sagittal spinopelvic alignment were assessed using radiography, and a correlation was observed between T1 slope (T1S) and lumbar mismatch (coefficient of 0.28, P = 0.047). Then, cervical sagittal alignment was evaluated using CT and sagittal spinopelvic alignment using radiography, and no correlation was observed between PI and thoracic inlet angle or cervical mismatch with lumbar mismatch. CONCLUSION: In asymptomatic patients, in whom cervical sagittal alignment and spinal-pelvic alignment were evaluated, only a positive correlation was found between lumbar mismatch and T1S, which lacks clinical significance. No concordance was identified between lumbar mismatch and cervical mismatch. Therefore, it is inferred that there is an independence between the sagittal spine-pelvic alignment with respect to the sagittal cervical alignment.