The anatomy of lumbar spondylosis.

To identify the major osseous, ligamentous, and neural relations of the lumbar spine pertinent to understanding the pathogenesis, diagnostic imaging, and therapy of lumbar spondylosis, 25 bony lumbar spines and 25 intact cadaver spines were studied both qualitatively and quantitatively. Pedicle anteroposterior dimension and obliquity and the relative interarticular process-interpedicle dimensions were found to be important osteologic determinants of the presence and size of lateral recesses at different vertebral levels and of the increasing size of each lateral recess as it descends. The varying length and relations of the osteoligamentous nerve root canals at different lumbar levels are a function of a progressively earlier exit from the dural sac by the lower lumbar nerve roots. Both the osteoligamentous nerve root canals and their terminal intervertebral canals showed significant normal narrowing at the level of the opposed intervertebral discs and facet joint capsules. This caused the normal nerve root canals to have a beaded appearance and the osteoligamentous intervertebral canals to have the appearance of long-necked gourds. These normally narrow areas correlate well with the spondylotic neural entrapment points. Narrowing of the disc interval is an important cause of many of the interdependent degenerative changes in the lumbar spine. Hence, its reconstitution should be a major goal of spondylotic surgery.