Narrowness of the recessus lateralis in the lumbar region of the spine as cause of the nerve-root compression in narrowing of the intervertebral discs (author's transl)

The intense radicular pain of sciatica may result from nerve root entrapment in a narrowed lateral vertebral recess without discal herniation. In such cases relief of pain is achieved by unroofing the lateral recess and excising the overhanging portion of the superior articular facet, without removing the disc. The narrowing of the lateral recess is congenital, but the compression of the root occurs first in adult life. The thinning of the disc causes backward displacement of the vertebral body above and forward displacement of the cranial articular facet of the vertebral body below the thinned disc. In a large lateral recess such subluxation does not cause any entrapment of the root. If the lateral recess is congenitally narrowed the root is tightly wedged laterally and sometimes can be decompressed only by a complete arthrotomy. The same entrapment can occur as a consequence of removing of a disc (pseudorecurrence).