Nodule of the Ligamentum Flavum as a Cause of Nerve Root Compression

Abstract

NORMALITIES of the l igamentum flavum have been related to the common low back disorder of cauda equina radiculopathy in lmnbar spondylosis. 3'<~~ Pat ients with lumbar spondylosis complain of leg fatigue, numbness, and occasionally bladder discomfort and voiding difficulties related to ambulation. Because of these symptoms, a t tent ion is often directed to vascular insufficiency of the legs rather than to a spinal abnormali ty. The l igamentum flavum lies between the vertebral laminae and is a t tached to the superior margin of the laminal arch below and at the center of the undersurface of the laminal arch above. Lateral ly it extends to and enters into the formation of the joint capsule between the articular facets and their intervertebral foramina. Medially it blends with the interspinous ligament and extends the entire length of the vertebral canal, n The l igamentum flavum is normally composed of elastic tissue which appears yellow. Embryologically, elastic tissue differentiates later than collagen fibers, but in the same general manner. The elastic tissues develop and merge into dense plates or collect into compact elastic bundles about the sixth month of development. 2 The thickness of the l igamentum flavum varies, the thickest portion being located medially. Measurements in the lumbar area have been reported, and thickness in this area does not vary significantly between the individual lumbar spaces tha t have been measured. 9,13 Since the anteroposterior diameter of the lumbar spinal canal cannot be well appreciated on routine radiographs, evaluation of the effect of hyper t rophy of the l igamentum flavum is difficult.