Variations of cervical lordosis and head alignment after pedicle subtraction osteotomy surgery for sagittal imbalance

Introduction The variations of the cervical lordosis after correction of sagittal imbalance have been poorly studied. The aim of our study is to verify whether the cervical lordosis changes after surgery for sagittal imbalance.Materials and methods Thirty-nine patients were included in the study. Cervical, thoracic and lumbar spine, pelvic and lower-limb sagittal parameters were recorded. The cranial alignment was measured by the newly described Cranial Slope.Results The global cervical kyphosis (preop -43° postop -31.5°) and the upper (preop -24.1°, postop -20.2°) and lower cervical kyphosis (preop -18.1°, postop -9.2°) were significantly reduced after surgical realignment of the trunk. A positive linear correlation was observed between the changes in T1 slope and the lower cervical lordosis, and between T1 slope and the global cervical alignment.Conclusions The cervical lordosis is reduced by surgical correction of malalignment of the trunk, suggesting an adaptive role to maintain the head’s neutral position.