An Applied Anatomical Study Of A Novel Extradural Nerve Anastomosis Technique For Restoration Of The Upper Trunk Avulsion Of Brachial Plexus

Introduction: Brachial plexus root avulsion injury is the most serious type of peripheral nerve injury.Nerve transfer is considered as the main method for treating barchial plexus avulsion injury.The current treatment is challenging and has many limitations.Firstly,some of anastomosis techniques need nerve grafts to reach the insufficient distance between the recipients and donors.What's more,the previous techniques of nerve transfer belonged to mixed nerve anastomosis,which can't achieve a satisfactory effect.In order to solve the problems of the disparate nerve matching between recipients and donors and excessive length of a grafted segment,it is critical to find a more appropriate technique for "accuracy anastomosis"(motor-to-motor nerves and sensory-to-sensory nerves)without other nerve grafts.In this study,we attempted to demonstrate,by an anatomical and histological study in human specimens,the feasibility of a new nerve transfer technique for restoration of the upper trunk avulsion of brachial plexus without opening the spinal dura mater.Part 1 Anatomical study of the extradural nerve roots in the cervical segment Objective: The goal of this study was to provide an anatomical basis for treating brachial plexus nerve root avulsion by the anatomical study of the extradural nerve roots in the cervical segment.Methods: Six fresh frozen cadavers(12 sides)were used in the study.The distance between the nerve root outlet and ganglion center,the distance between adjacent nerve root outlets,and the gross anatomy of the extradural spinal root were measured with a surgical microscope.The diameters of the ventral roots and the dorsal roots were measured from C3 to T1.The numbers of nerve fibers of ventral roots and dorsal roots from C3 to C8 were measured by immunohistochemical staining.Results: Spinal nerves are composed of ventral and dorsal roots in their corresponding spinal cord segments and the extradural ventral roots still lie ventrally to their corresponding dorsal roots.The average distance between the nerve root outlet and ganglion center increased from C3 to C6 and then decreased from C6 to C8.The distances between the adjacent nerve root outlets ranges from 10.36 to 18.4 mm at different spinal levels.The diameter of C6 ventral root(VR)(1815.8±235.9?m)was the largest in all measured segments.As for the dorsal root(DR),the diameter of nerve roots was largest at C6(2931.3±567.4?m).The ventral root of C7(7445 ±1261,ranging from 6328 to 8311)contained the most nerve fibers in each segment,the dorsal root of C7(17115±3424,ranging from 13312-22165)also contained the most nerve fibers among the cervical nerve roots.There was no significant difference between the right and left sides.Conclusion: The anatomical characteristics of the extradural spinal nerve roots in the cervical spine segment was studied in detail.The results of this study will provide important data references and theoretical basis for the treatment of brachial plexus injury by the extradural nerve root transfer technique.Part 2 Rapid identification of human cervical spinal ventral and dorsal roots by an acetylcholinesterase antibody-based quartz crystal microbalance device Objective: In this study,we tried to distinguish the ventral and dorsal roots of humans and detect the levels of the acetylcholinesterase(ACh E)in spinal roots of humans in the cervical segment.Methods: Three human fresh frozen cadavers were provided by the department of anatomy of Nanjing Medical University.After the exradural nerve roots were exposed,the ventral and dorsal roots were carefully separated.1mm of the nerve roots were cut off for sample detection,5mm of the nerve roots were cut off for double immunofluorescent staining.The regional expression of acetylcholinesterase in ventral and dorsal roots was determined by double immunofluorescent staining of Neurofilament 200(NF200)and anti-acetylcholinesterase antibody.Solutions of acetylcholinesterase at 0,0.25,0.5,1.0,2.5,5.0,10.0?g/ml and the sample solutions of ventral and dorsal roots were detected by the acetylcholinesterase antibody-based quartz crystal microbalance device.Results: The neurons,indicated by green fluorescence,were labeled with NF200.The neurons labeled with AChE,were indicated by red fluorescence.In the ventral roots,all nerve fibers were labeled by green and red fluorescence.In the dorsal roots,although all nerve fibers were labeled by green fluorescence,little nerve fibers were labeled by red fluorescence.Various solutions of ACh E were flowed over the immunosensors during which the frequency was recorded in real time.The correlation between frequency change and concentration of ACh E was analyzed and a linear regression equation was developed between frequency change and concentration of ACh E(0.5-10.0 ?g/ml).The value of frequency change of the ventral root was always greater than that of the corresponding dorsal root(p<0.05).Conclusion: These results clearly demonstrate that the quartz crystal microbalance sensor can be used as a rapid,highly sensitive and accurate detection tool for the quick identification of spinal nerve roots.Part 3 Coaptation of C4 to C5 and C7 to C6 for restoration of the isolated upper trunk avulsion of brachial plexus Objective: To determine the anatomical feasibility of transferring the C4 ventral and dorsal roots to C5 ventral and dorsal roots,and C7 ventral and dorsal roots to C6 ventral and dorsal roots as a method for restoring the upper trunk avulsion of brachial plexus.Method: In this study,three fresh frozen cadavers were used.The feasibility of exposing the C4-C7 extradural nerve roots by the limited laminectomy,isolating the VR and dorsal roots from each extradural nerve root and transferring the C4 ventral and dorsal roots to C5 ventral and dorsal roots,C7 ventral and dorsal roots to C6 ventral and dorsal roots were assessed.The pertinent distances in each specimen were measured.Results: The limited laminectomy was performed to expose the C4 to C7 extradural nerve roots.The ventral roots could be isolated from each extradural nerve root at the location of the dorsal root ganglion and there were some connective tissues separating the VRs from the corresponding dorsal root ganglion.The C4 ventral and dorsal roots have sufficient lengths to be transferred to C5 ventral and dorsal roots without grafting.The C7 ventral and dorsal roots have sufficient lengths to be transferred to C6 ventral and dorsal roots without grafting.Conclusion: This study demonstrated that transferring of the C4 ventral and dorsal roots to C5 ventral and dorsal roots,and C7 ventral and dorsal roots to C6 ventral and dorsal roots is surgically feasible as a method for restoring the upper trunk avulsion of brachial plexus.