Variation of C1 spinolaminar line and prevalence of C1 stenosis in normal population.

BACKGROUND: The variation of C1 spinolaminar line in normal population is not fully understood. The relative position of C1 lamina to C3-C2 spinolaminar line is reported as good screening tool for determination of C1 canal stenosis.

OBJECTIVE: To determine the variation of C1 spinolaminar line and find the prevalence of C1 canal stenosis in normal population using C3-C2 spinolaminar test.

MATERIALS AND METHODS: Three hundred and fifteen lateral cervical radiographs from 315 volunteers without neurological symptoms were analyzed. The relative position of C1 spinolaminar line was determined by C3-C2 spinolaminar and considered positive if C1 lamina lay ventral to C3-C2 line. C1 space available for cord (SAC) was measured from posterior border of dens to the C1 lamina to determine the sagittal diameter.

RESULTS: The mean sagittal spinal canal diameter of C1 was 22.2 mm (13-26 mm). Of 315, 14 (4.4%) had positive, 184 (58.4%) had neutral, and 117 (37.1%) had negative C1 spinolaminar line in relation to C3-C2 line. The mean SAC among positive group was 14.9 mm compared to neutral and negative groups which were 22.2 and 23.3 mm, respectively. 21.4% of positive group had SAC of less than 12 mm. The 92.8% of positive C1 spinolaminar line was found in age ≥ 60 years.

CONCLUSION: In a normal population, 4.4% has positive C1 spinolaminar line. The C1 stenosis is more prevalent in positive C1 spinolaminar line group.