A practical radiographic visual estimation technique for the prediction of developmental narrowing of cervical spinal canal

Abstract

To determine if visual spinal canal percentage of facet overlap could be used as a rapid visual pre-screening test to detect developmental bony spinal canal narrowing on lateral cervical radiographs. Lateral cervical spine radiographs with radiology report documenting developmental narrowing of the spine canal were retrospectively identified. Cohort was supplemented with additional images without such documentation. Utilizing a radiology work station, one reader (Orthopaedics) calculated the Torg ratio at C3-C6. Two readers (Radiology, Primary Care Sports Medicine) visually estimated percentage (≥80, ≥90, 100%) of spinal canal overlaid by facet articulations C3-C6 for all cases independently. Statistical analysis included accuracy tests and kappa test for comparing the gold standard and inter-, intra-observer reliability, respectively. 96 lateral images were included; 25 had abnormal radiology reports. High specificity (range, 91-93%) and true negative predictive values (range, 88-93%) achieved consistent statistical significance for relationship between facet/canal overlap and Torg ratio for both combined and individual data points. Sensitivity values (range, 59-75%) showed a trend toward association, with statistical significance for only the C3 level at 80% overlap. Interobserver agreement was substantial. Intra-observer reliability was moderate to perfect. Visual estimation of percentage of facet overlap of the spinal canal is a valid tool to identify individuals with potential developmental narrowing of the spinal canal as a screening prompt to select which patients may need formal calculation utilizing accepted metrics. Advances in knowledge Visual estimation of percentage of facet overlap from lateral radiographs can predict developmental narrowing of cervical spinal canal.