➢ Cervical sagittal alignment is associated with patient-reported outcomes, with higher T1 slope-cervical lordosis mismatch and greater C2-C7 sagittal vertical axis correlating with greater disability and worse health-related quality of life.➢ Cervical alignment must be interpreted alongside global sagittal balance, as cervical posture interacts with thoracic and spinopelvic alignment and compensatory mechanisms.➢ Both anterior and posterior cervical fusion can influence sagittal alignment, but optimal outcomes depend on alignment-conscious planning tailored to deformity morphology and spinal flexibility.➢ Preserving or restoring physiologic cervical alignment reduces the risk of postoperative imbalance and adjacent-segment disease, supporting alignment-guided 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.

Ossification of the nuchal ligament (ONL) is a common but frequently overlooked radiographic finding on lateral cervical spine imaging, characterized by ectopic bone formation within the nuchal ligament, most often at the C4/5 and C5/6 levels. Although usually asymptomatic, ONL has been associated with cervical spondylosis, segmental instability, and, importantly, a markedly increased risk of coexisting ossification of the posterior longitudinal ligament (OPLL), a condition with potential for progressive myelopathy. We conducted a narrative review of the PubMed-indexed literature on the anatomy, epidemiology, classification, and clinical significance of ONL, illustrated with the case of a 61-year-old female who presented with neck stiffness and headache in the context of habitual mobile phone use of 10 hours per day. Lateral cervical radiography demonstrated loss of normal cervical lordosis, moderate degenerative disc disease most severe at C5/6, and ossification of the ligamentum nuchae posterior to C4 and C5, consistent with moderate cervical spondylosis. She improved with four weeks of care. This case illustrates the classic radiographic and clinical profile of ONL in the setting of reported prolonged device use and forward head posture, highlighting a possible contributing mechanical factor. Given the strong statistical link between ONL and OPLL, primary healthcare providers who incidentally identify ONL on lateral cervical radiographs should consider it a clinical marker warranting careful neurological evaluation. Advanced cross-sectional imaging (CT or MRI) is not automatically indicated for isolated, asymptomatic ONL, but should be considered when neurological signs or symptoms, suspected myelopathy, progressive deficits, trauma, or specific manual therapy safety considerations arise.