LUMBAR FORAMINAL STENOSIS - CRITICAL HEIGHTS OF THE INTERVERTEBRAL DISKS AND FORAMINA - A CRYOMICROTOME STUDY IN CADAVERA

One hundred lumbar intervertebral foramina from eighteen spines of fre sh cadavera were studied to assess the relationship between compressio n of the nerve root and the height of the intervertebral disc and the morphological characteristics of the intervertebral foramen as determi ned on cryomicrotome sections. The critical posterior disc height and the critical foraminal height that were associated with entrapment and compression of the nerve root were determined. Significant positive c orrelations were demonstrated between compression of the nerve root an d the posterior disc height, the foraminal height, and the foraminal c ross-sectional area for the four intervertebral levels between the sec ond lumbar and first sacral vertebrae, Nerve-root compression was evid ent in twenty-one of the 100 foramina, in eight of the ten foramina in which the posterior disc height was four millimeters or less, and in four of the five foramina in which the foraminal height was fifteen mi llimeters or less. These critical dimensions may be indicators of fora minal stenosis in the lumbar spine, However, compression of a spinal n erve root does not always cause sciatica, and the clinical findings mu st always be taken into account when a diagnosis of stenosis is consid ered.