Horne et al. seem to have developed such a tool, as they describe in the July 20, 2016 issue of The Journal of Bone & Joint Surgery. Using a canal diameter of <12 mm, as measured by computed tomography (CT), as the definition of developmental cervical stenosis, the authors made detailed measurements of lateral cervical radiographs from 150 adult patients. They then calculated several ratios from those measurements and compared the ratios to the “true” CT-determined canal diameter. After analyzing the predictive value of the ratios, they determined that:
- At C5, a ratio of lateral mass-to-posterior vertebral body distance (LM) to spinolaminar line-to-vertebral body (canal) diameter (CD) ≥0.735 indicated cervical stenosis at any level from C3 through C6, with a sensitivity of 76% and a false-positive rate of 20%.
- This LM/CD ratio minimizes the confounding effects of patient size, sex, and ethnicity, which have hampered the statistical strength of earlier predictive measurements, such as the Torg-Pavlov ratio.
The authors conclude that the LM/CD ratio “may help practitioners to assess the risk of underlying cervical stenosis and the need for additional imaging or referral to a surgical specialist,” but they are quick to add that “this ratio should not be used in isolation for clinical operative decision-making or for withdrawing athletes from sports participation.”