Transforaminal ligament may play a role in lumbar nerve root compression of foraminal stenosis

Lumbar foraminal stenosis is a common pathological change, and lumbar nerve root compression in stenotic foramina was recently considered as one of the main causes of low back pain and leg pain. However, the exact mechanism of lumbar nerve root compression in foramina is still not clear. Previous studies indicated that loss of the intervertebral disc height could reduce the cross-sectional area of lumbar foramina, while lumbar nerve root compression by boundaries of foramina has not been observed in experimental reduction of the intervertebral disc height. Given the close anatomic relationship between transforaminal ligaments and lumbar nerve roots, we hypothesize that transforaminal ligament can be the leading cause of lumbar nerve root compression in foraminal stenosis. We also propose that there are two possible mechanisms of lumbar nerve root compression by transforaminal ligaments: (1) nerve roots are compressed by the transforaminal ligament which moves downward with the loss of the intervertebral disc height; (2) pathological transforaminal ligaments increase the risk of nerve root compression in foramina.