Radiography of the hyperextended lumbar spine: an effective technique for the demonstration of discal vacuum phenomena.

A prospective evaluation of dynamic lateral lumbar spine radiographs in the erect position in 52 symptomatic patients over the age of 50 years revealed vacuum phenomena in intervertebral discs in 46%. Their frequency was greatest at the L5-S1 spinal level and decreased progressively at higher lumbar levels. Analysis of the dependency of discal vacuum phenomena on spinal position during radiography revealed that hyperextension detected all such phenomena; radiography in the neutral position detected 73% of vacuum phenomena, whereas that obtained with the spine flexed revealed 20% of vacuum phenomena. Our results indicate that lateral radiographs of the hyperextended lumbar spine are useful in the differential diagnosis of intervertebral osteochondrosis (degenerative disease of the nucleus pulposus) and infection.