Correlation between the ossification of nuchal ligament and clinical cervical disorders

This is a correlation analysis between severity of the ossification of the nuchal ligament (ONL) and clinical cervical disorders including neck dysfunction, cervical malalignment, and morphologic changes of the cervical neural foramen (CNF). The clinical effects of ONL on active range of motion (AROM) of neck, cervical radiculopathy, abnormal cervical curvature, and the degree of CNF stenosis in patients with painful neck stiffness are investigated. Studies have investigated the predisposing factors to cervical dysfunction and degenerative disorders; however, few studies have examined the influence of the ONL on neck function and cervical spine. A total of 31 participants with painful neck stiffness were recruited. They accepted measurement of cervical AROM and serial cervical radiographs at anterior-posterior view, lateral view, and bilateral oblique views. Parameters of radiographs measurement included cervical lordotic curve, and cross-sectional areas (CSA) of the ONL and CNF (C2-C3, C4-C5, C5-C6, and C6-C7 levels). The ratio of CSA of the lower CNF (C4-C5, C5-C6, C6-C7) to CSA of the upper CNF (C2-C3) was used as a CNF stenosis ratio. The correlations of ONL size, neck symptoms, cervical AROM, lordotic curve, and CNF stenosis ratio were analyzed. More than half of all patients were positive in cervical root signs and prone to have larger ONL. Neck AROM of all participants was significantly below normal average in all directions, and a moderate negative association was found between the ONL CSA and AROM in flexion-extension. Most patients had moderate loss of cervical lordotic curve despite there being no significant correlation between ONL CSA and cervical curvature. Moreover, CNF stenosis ratio significantly negatively correlated with ONL CSA. Patients with larger ONL had more severe cervical radiculopathy, more stiffness in flexion-extension direction, more complex degenerative change of spine, and worse CNF stenosis.