The Anatomy of Dorsal Ramus Nerves and Its Implications in Lower Back Pain

This article reviews the relationship between the spinal dorsal ramus system and low back pain, including the anatomy, clinical findings, pathogenesis and treatment of low back pain mediated by spinal dorsal ramus and zygapophysial (facet) joint syndrome. Each spinal dorsal ramus arises from the spinal nerve and then divides into a medial and lateral branch. The medial branch supplies the tissues from the midline to the zygapophysial joint line and innervates two to three adjacent zygapophysial joints and their related soft tissues. The lateral branch innervates the tissues lateral to the zygapophysial joint line. The clinical pain presentations follow these anatomic distributions, which can be used for localizing the involved dorsal ramus. The diagnosis can be confirmed by performing a single dorsal ramus block that results in relief of pain and muscle spasm. Etiologically, any factor that stimulates the spinal dorsal ramus can cause low back pain, which is distinct from zygapophysial joint syndrome. Clinically, L1 and L2 are the most common sites of dorsal rami involvement. Treatment includes spinal dorsal ramus injection therapy and percutaneous neurotomy. Summarily, irritation of the spinal dorsal ramus system is a potential source of low back pain. Based on the anatomy and clinical presentation, the involved spinal dorsal ramus can be localized and treated.