Adult Cervical Deformity: Contemporary Evaluation, Classification, and Surgical Decision-Making

➢ Standing full-spine radiographs are mandatory for cervical deformity evaluation; key alignment targets include cervical sagittal vertical axis (cSVA) of ≤40 mm, T1 slope minus cervical lordosis (T1S - CL) of <15°, and a chin-brow vertical angle (CBVA) between -10° and +10° relative to the true vertical. The achievement of these thresholds is independently associated with better patient-reported outcomes, whereas values outside these ranges are associated with worse disability and quality-of-life scores.➢ The Kim-International Spine Study Group (ISSG) morphology-based classification, which identifies 4 patterns (flat neck, focal, cervicothoracic, and coronal or complex) from standing and dynamic extension radiographs, provides a reproducible morphology and flexibility-based framework that informs operative planning and has demonstrated superior interrater and intrarater reliability over prior descriptive systems; final surgical decisions integrate flexibility, neurological status, global alignment, bone quality, and patient-specific factors, and the direct impact of this classification on surgical outcomes requires further prospective validation.➢ Surgical planning is stratified by the intended lower instrumented vertebra (LIV) (Type 1: LIV T2-T4; Type 2: within the cervical spine or cervicothoracic junction; Type 3: extending past the thoracolumbar junction) and by whether the deformity is ankylosed, which determines the need for osteotomy.➢ Overall complication rates exceed 50% in prospective multicenter data; systematic risk mitigation, including neuromonitoring, tranexamic acid, staged approaches, and frailty-based patient selection, is essential for safe outcomes.➢ Despite high complication rates, the surgical correction of cervical deformity yields clinically meaningful improvements in pain and health-related quality of life at 1 year in appropriately selected patients; realistic goal-setting and individualized alignment targets are the keys to durable success.