Anatomical study of the lateral branches of lumbar and sacral dorsal ramus

English Keywords:Sacroiliac joint  Innervation  Clinical anatomy

English Abstract:

  【Abstract】 Objectives: The purpose of this study was to describe the anatomical characteristics of the innervation of the dorsal aspect of sacroiliac joint and to provide anatomical data for the radiofrequency ablation of lateral branches of lumbosacral nerve. Methods: 7 lumbosacral specimens were collected from 7 embalmed adult cadavers(aged 42~68 years, mean 54.3±8.0 years) which included five males and two females. All the specimens were sourced from Southern Medical University. The surface skin, multifidus muscle, gluteus maximus, gluteus medius, and gluteus minous muscle were routinely dissected from the plane of L3/4 intervertebral disc till the end of the specimens, the soft tissues surrounding the dorsal lateral branches of the lumbosacral nerve were removed under an operative microscope as well to expose the lateral branches of the dorsal rami of L3-L4. The angles between the lateral branches of the dorsal rami of S1-S4 and the longitudinal axis at a distance of 8mm from the posterior sacral foramens, as well as the angles between the lateral branches of the dorsal rami of L4-L5 and the frontal axis were measured. The distance between the lateral branches of the dorsal rami of sacral nerve and the posterior midline at a distance of 8mm from the posterior sacral foramen were also measured. Results: A total of 65 lateral branches of sacral dorsal rami were identified in the 7 specimens, with 16, 19, 19, and 11 lateral branches of the dorsal rami of S1-S4, respectively. The angles between the lateral branches of the dorsal rami of S1-S4 and the longitudinal axis at a distance of 8mm from the posterior sacral foramens were 38°±9°, 45°±13°, 40°±10°, and 45°±7° respectively. And the distances between the lateral branches of the dorsal rami of S1-S4 and the posterior midline at a distance of 8mm from the posterior sacral foramen were 21.3±3.0mm, 24.0±3.5mm, 21.7±2.8mm, and 22.7±3.0mm, respectively. 12 lateral branches of the dorsal rami of L4 and 14 lateral branches of the dorsal rami of L5 were found. The main trunk length of the lateral branches of the dorsal rami of L4 was about 26.5±2.6mm, which of L5 was about 25.7±5.8mm. The angles between the lateral branches of the dorsal rami of L4-L5 and the frontal axis were about 72°±2° and 66°±4°, respectively. Conclusions: The dorsal sacroiliac joint was mainly innervated by the lateral branches of the dorsal rami of L5-S4, occasionally by the lateral branches of the dorsal rami of L4.