Brachial Plexus Nerve Root Spinal Anatomy Observations

[Objective] To observe the configuration and traits of the ventral roots and dorsal roots ofbrachial plexus in the spinal canal, in order to clarify the spatial relationship and significancebetween the ventral roots and dorsal roots and the intervertebral foramen, so it will provideanatomical basis for diagnosis and treatment of roots avulsion of brachial plexus andcervicalspondylotic radiculopathy.[Method] We selected 15 cervicothoracic spine specimens of adult embalmed cadaver. Weopened the spinal canal, displayed the bilateral brachial plexus, measured the sectional area ofthe spinal nerve at the outer orifice and inner orifice, the plane area of the outer orifice and theup to down diameter, anteroposterior diameter of the intervertebral foramen. The number of therootlets, the second roots and the roots, the length and the angle to the spinal cord of the ventralroots of brachial plexus, the distances of the origin of the ventural (dorsal) roots to the anterior(posterior) median sulcus were measured.[Result] From C₅ to C₈, the sectional area of the brachial plexus at the inner(outer) orificeincreased gradually, T₁ was the least. The sectional area of the brachial plexus at the inner(outer)orifice were 14.0±1.37 mm, 21.0±1.83mm for C₅ and 24.2±2.68 mm, 30.3±3.93mm for C₈respectively. The ratio of the sectional area of the brachial plexus at the outer orifice to the planearea of the outer orifice was about 1/3. From up to down, the number of the rootlets of thebrachial plexus decreased gradually, C₅ was the most in the anterior rootlets, which was 10.1±3.3, and C₆ was the most in the posterior one, which was 9.7±3.5. The length of roots were15.62±1.88mm. 12.73±1.77mm for C₅ and 22.33±2.16mm. 22.00±2.08mm for T₁ respectively.all data increased gradually, and the ventral roots were longer than the dorsal one. The length ofsegment A and segment B of roots became bigger from C₅ to T₁. The angle of the ventral roots tothe spinal cord were 60.25°for C₅ and 30.03°for T₁, from up to down, the data decreasedgradually.[Conclusion] 1. The location of the ligament at the intervertebral foramen to the nerve rootsplays an important role in the splitting of the nerve roots, and it decides the types of the injury of brachial plexus.2. Our results refers weather the cervicalspondylotic radiculopathy will happenor the severe degree of the symptoms will be decided in the ratio of the sectional area of thebrachial plexus at the intervertebral foramen to the plane area of the intervertebral foramen andposition of the spinal nerve at intervertebral foramen, not the plane area of the intervertebralforamen. 3. Our experiment measured the sectional area of the brachial plexus at the inner orifice,it will provide anatomical basis for radiological diagnosis of the cervicalspondyloticradiculopathy that happens at the inner orifice.