Introduction: Long-segment lumbar instrumentation extending to the sacrum or thoracolumbar junction is commonly performed for adult spinal deformity and degenerative conditions. While proximal junctional complications have been extensively studied, the compensatory changes in cervical alignment following long-segment lumbar fusion remain poorly understood. This study aimed to investigate the temporal changes in cervical sagittal alignment over three years following long-segment lumbar instrumentation.

Methods: A retrospective review was conducted on 30 patients who underwent long-segment posterior lumbar instrumentation extending to either the sacrum or thoracolumbar junction. Patients with previous cervical spine surgery or cervical pathology were excluded. Lateral standing radiographs of the entire spine were obtained preoperatively and at postoperative intervals up to three years. Cervical sagittal parameters including C2-C7 lordosis, C2-C7 sagittal vertical axis, and T1 slope were measured. Spinopelvic parameters including lumbar lordosis, pelvic tilt, and global sagittal vertical axis were also assessed. Clinical outcomes were evaluated using the Neck Disability Index and visual analog scale for neck pain.

Results: Patients demonstrated progressive loss of cervical lordosis and increased forward cervical inclination over the three-year follow-up period. These changes were more pronounced in patients with instrumentation extending to the sacrum compared to the thoracolumbar junction. Greater postoperative lumbar lordosis correction and larger global sagittal vertical axis were associated with more significant cervical alignment changes. Despite these radiographic changes, clinical neck symptoms remained mild in most patients at final follow-up.

Conclusion: Long-segment lumbar instrumentation is associated with progressive compensatory changes in cervical sagittal alignment over three years, particularly in patients with instrumentation to the sacrum. Despite radiographic changes, most patients maintain adequate cervical compensation without significant clinical symptoms. Understanding these changes may help in preoperative planning and patient counseling