Identifying the Optimal Radiographic Parameter for CCI Diagnosis Using a Healthy Population

Introduction: Craniocervical instability (CCI) commonly affects patients with connective tissue disorders due to ligamentous laxity. Consequences of CCI result in autonomic, sensory, and motor deficits. Currently, radiographic guidelines to diagnose CCI are lacking. Measurements currently considered for the diagnosis of CCI include: the clivo-axial angle (CXA), basion-dens interval (BDI), basion-axis interval (BAI), atlanto-dental interval (ADI), perpendicular basion to the inferior aspect of C2 (pbC2), hard palate to C1 (HPC1), and hard palate to C2 (HPC2). Using a healthy population, the primary goal of the project was to use the coefficient of variance (CoV) to identify the most effective radiographic marker to serve as a diagnostic tool for CCI and provide potential cut-off values.

Methods: Cervical MRIs were used to identify the basion via overlay of the image to be analyzed (CT or X-ray). Measurements were obtained for supine CT and X-rays in the neutral, flexion, and extension positions. Descriptive statistical analysis methods used include means and standard deviations. We calculated the coefficient of variance (CoV) to determine the suitability of a measurement to serve as a reference value.

Results: Our cohort of 72 patients was comprised of 44 (66.1%) females and 58 (80.6%) were Caucasian. Average (in mm) and associated standard deviations were as follows (supine/neutral/flexion/extension): CXA – 58.2°±23.6°) / 157°±21.8° / 156°±24.2 / 169°±18.2°; BDI – 5.5±2.8mm / 6.3±5 mm / 5.6±4.2 / 7.4±5.4mm; BAIs – 5.5±4.8 mm / 6.6±5.6 / 7.4±6.2 mm / 6.0±5.2 mm; ADI –1.4±1.2 / 1.3±1.2 / 1.6±1.4 / 1.4±1.4; HPC1 – 47.1±14.4 / 43.9±13.8 / 42.0±15.2 / 52.8±14; HPC2 – 65.8±13.2 / 73.0±19.9 / 66.6±20.4 / 81.9±19.2. CXA had the lowest CoV for its associated values: 0.41 / 0.14 / 0.16 / 0.11.

Conclusion : We utilized a healthy cohort with cervical imaging to establish measurement ranges for 6 measurements often used to evaluate CCI. Our results demonstrate that CXA measurements, specifically in the extension position, may serve as a potential diagnostic tool for CCI.