Posterior Branches of Lumbar Spinal Nerves - part II: Lumbar Facet Syndrome - Pathomechanism, Symptomatology and Diagnostic Work-up.

Posterior branches of the lumbar spinal nerves are the anatomic substrate of pain in the lower back, sacrum and the gluteal area. Such pain may be associated with various pathologies which cause pain in the posterior branches of the lumbar spinal nerves due to entrapment, mechanical irritation or inflammatory reaction and/or degeneration. The posterior branches are of significant functional importance, which is related to the function of the structures they supply, including facet joints, which are the basic biomechanical units of the spine. Low back pain caused by facet joint pathology may be triggered e.g. by simple activities, such as body rotations, unnatural positions, lifting heavy weights or excessive bending as well as chronic overloading with spinal hyperextension. Pain usually presents at the level of the lumbosacral junction (L 5 -S 1 ) and in the lower lumbar spine (L 4-5 , L 3-4 ). In the absence of specific diagnostic criteria, it is only possible to conclude that patients display tenderness at the level of the affected facet joint and that the pain is triggered by extension. Differential diagnosis for low back pain is difficult, since the pain may originate from various structures. The most reliable method of identifying Lumbar Facet Syndrome has been found to be a positive response to an analgesic procedure in the form of a block of the medial branch or intraarticular injection. There appear to be good grounds for conducting further studies and developing unequivocal diagnostic tests.