The Research About The Anatomic Structure Of Extradural Spinal Root For Its Anastomoses In Treating Neurogenic Bladder After Spinal Cord Injury

BackgroundBladder dysfunction caused by spinal cord injury (SCI) remains a significant worldwide challenge. Intradural anastomosis of the spinal root has made breakthrough progress in treating neurogenic bladder in spinal cord injury."Artificial bladder reflex" means recovering the bladder function by residual nerve root to sacral nerve root anastomosis. However, because of the complex surgical procedures and extensive bony destruction, its clinical use is not widely promoted.PurposeTo ascertain the anatomical parameters of the extradural spinal root and to demonstrate the feasibility of spinal root anastomoses without opening the spinal dura mater.MethodsNine formalin-fixed cadavers were used. The distance between the nerve root outlet and ganglion center, the neighboring nerve root-outlet distance, and the gross anatomy of the extradural spinal root were measured with a surgical microscope. The number of nerve fibers from the T7to S4ventral roots (VRs) was calculated by immunohistochemical staining. ResultsThe longest and shortest lengths of the extradural spinal root were observed at the S4and T7levels, with average values of33.29and6.06mm, respectively. The longest distance between the adjacent nerve root outlets was observed at L1-L2(mean,29.16mm), and shortest at S3-S4(mean,11.79mm). After leaving the dural sac, the spinal root descends in the spinal canal until reaching the corresponding intervertebral foramina, and the motor nerve roots still lie ventrally to the sensory nerve roots. The largest and smallest numbers of nerve fibers were observed at the L3and S4levels (mean,9169and1356, respectively).ConclusionThe dorsal roots and VRs can both be successfully harvested and identified outside the dural sac. The S1VR can be anastomosed to the S2VR extradurally without nerve grafts. For extradural neuroanastomosis of the thoracic VRs to the S2VR, a nerve graft is required. In addition, there are a sufficient number of nerve fibers for functional bladder recovery at the T7-T12and S1levels. This study supports the feasibility of extradural spinal root anastomosis as a modified surgical method for treating neurogenic bladder.