Clinical Anatomy and Measurement of the Medial Branch of the Spinal Dorsal Ramus

Percutaneous block and neurotomy of the medial branch of the spinal dorsal ramus has shown excellent results in treating facet joint-mediated low back pain. This study aimed to describe the clinical anatomy of the medial branch and its measurements. We dissected the lumbar spine of 12 adult cadavers (24 sides) and measured the distances between the medial branch and various anatomical landmarks. The distances were compared between L1 and L5 vertebrae. The distance between the dorsal ramus bifurcation and the superior border of the root of the transverse process was 3.52 ± 1.15 mm, 3.63 ± 1.36 mm, 3.46 ± 1.31 mm, 3.38 ± 1.24 mm, and 1.87 ± 0.88 for L1 to L5, respectively. The medial branch of the dorsal ramus is enclosed in a fibro-osseous canal bounded by the accessory process, the mammillary process, and the mammilloaccessory ligament. For the percutaneous treatment of block and neurotomy, the first choice of target is the medial branch fibro-osseous canal near to the accessory process. The accessory process is not displayed in x-ray films; therefore, the junction of the superior articular process and the root of the transverse process can be targeted.