Cervical instability in cervical spondylosis patients: Significance of the radiographic index method for evaluation

BACKGROUND: Cervical spondylosis is one of the most common causes of cervical instability. Various methods are used for measuring cervical instability on X‑ray films. The purpose of this study was to assess the application of the radiographic index method to analyze the radiographic features of cervical spondylosis instability. MATERIAL AND METHODS: Digitized dynamic radiographs of 121 subjects with cervical spondylosis were retrospectively retrieved. The cervical spondylosis patients were divided into two groups according to the symptoms: patients with positive neurological deficits with and without neck symptoms (group I, n = 62) and patients with neck symptoms only (group II, n = 59). A total of 62 healthy subjects were assigned to the control group (group III). The radiographic indices of cervical curvature, the full flexion to full extension ranges of motion (ROM) and horizontal displacement of the three groups were analyzed and compared with each other. RESULTS: On flexion-extension views there were significant differences (p = 0.00000 [significance of cervical lordosis on flexion view between the three groups], p = 0.00271 [significant difference of cervical lordosis between the three groups on extension view]) between the three groups concerning the cervical lordosis: group I had the least cervical curvature, followed by group II and group III. The full flexion to full extension ranges of motion for group I was significantly decreased (p = 0.0039) when compared with group II and group III. The horizontal displacement at each segmental level (except C2/C3) was significantly higher in group I than that of the other two groups. CONCLUSION: With the application of the radiographic index method, cervical spine lordosis, the full flexion to full extension ROM, horizontal displacement, and cervical instability can be accurately illustrated. Cervical spondylosis is an age-related, wear and tear change of the spine that occurs over time. The index of the horizontal displacement ≥0.3 is suggestive of cervical instability.