Radiographic versus direct measurements of the spinal canal at lumbar vertebrae L3-L5 and their relations to age and body stature.

The role of the narrow lumbar spinal canal in back and sciatic pain is well established. The accuracy of measurements obtained from lumbar radiographs was therefore analyzed in lumbar spine specimens taken from 132 male cadavers. After removal of soft tissues, the same distances were measured on the bones of 80 specimens. Comparisons were made after correction for magnification, the radiographic measurements of interpedicular distances being, on average, 2 mm greater at L3 than the osteologic ones and 4 mm greater at L5. Interarticular distances, midsagittal diameters, and pedicular lengths were, on average, 1 mm greater and foraminal anteroposterior measurements 1 mm less than the osteologic ones. Body stature correlated with interpedicular and interarticular distances, pedicular length, and foraminal anteroposterior measurements. In older age groups, the midsagittal diameter tended to be reduced. A number of correlations were found between the five measurements, e.g. between the anteroposterior diameter of the intervertebral foramen and the pedicular length. Measurements in the transverse plane were independent of those in the anteroposterior plane. These results confirm and amplify preliminary observations and indicate the potential value of simple measurements on lumbar spine films as an alternative to more sophisticated and expensive radiologic investigations.