The Experimental Study Of The Functional Reserve Of Peripheral Nerves

Brachial plexus root avulsion is one of the obstinate diseas in peripheral nerve neurosurgical fields, with high mutilation rate. On treatment, the nerve transposition is the main method. Because the power nerves available are limited, and only a part function of several joints can be saved, the treatment results are not so satisfying. It is proved that power nerves of extracardiac brachial plexus were very limited. The success of nerve transposition within brachial plexus threw a light on exploring more power nerves. Especially to Oberlin's surgery, it is wide accepted for its quick restoration, minor secondary injury and favoring functional excise. While the maximum quantity of cut nerve bundle branches is suspect. The variance of cutting ratio and impact on donor nerve is remarkable.Object The study employed nerve microdissection, nerve tracing, histomorphology and electrophysiology methods to value function changes and compensation of corresponding nerve after removing a part of nerve bundle. To introduce the concept of functional reserve of peripheral nerve, approach the quantity of functional reserve of peripheral nerve, decide the optimal level, location and cutting ratio, and interpret the mechanism of the functional reserve and compensation,and building up the theory basic of nerve transposition with maximal ratio nerve bundle.Methods 1. Microdissection on the SD rats brachial plexus and their branches with acetic acid pickling and observe the construction, branches and dominate muscles. Measure the length of the musculocutaneous nerve truck, the proximal branches level and the ratio of an area of median nerve, radial nerve and ulnar nerve, and the length of the common trunk of median nerve and ulnar nerve. 2. Retrogradation tracing on proximal branches of the nerves the above nerves with DiI, and approach the experimental condition and its bionomics. Selectively nerve branches tracing and observe the regular pattern of the branches in nerves trunk and definite the safe location for bundle cutting. 3. Detect the influences on motoneuron, nerve trunk, and dominate muscles after cutting a certain part of nerve bundles with electrophysiology, pathomorphology and FCM methods, and definite the cutting ratio finally.Results 1. The brachial plexuses between rats and human being are very similar in origin of nerve roots, nerve segment construction and dominate muscles. The branch level of radial nerve is the highest, then is the median nerve, and that the ulnar nerve is the lowest. While the ratio of an area of radial nerve is the biggest one, the second is ulnar nerve, and the median nerve is the smallest. 2. DiI is the favorable bi-direction nerve tracer, with axis specificity and higher transport speed in vivo than in fixed one. It is suite to the study on distribution of the nerve fiber. 3. The anterograde tracing nerve fibers diffused in most or the whole nerves trunks while migrate downward, without independent bundle. The proximal nerve fibers of brachial plexus overlap frequently. The relic nerve fibers of injured brachial plexus diffused widely. The distribution area exceeds one half of the trunks, and about 70% cases distributed to the whole trunks. When retrograde tracing, we can see that the branches formed gradually. The more distance, the more diffused, and diffusing to the whole trunk is rare. So the lowest level is being. The lowest level of radial nerve is at the 80% of upper limbs, that the median nerve is 60%, and the ulnar nerve's is at meddle-down 1/3. On the location of tracing nerve fiber on the transaction, efficiency cutting area locates on the natural branches. 4. Partial injury of the trunks has minor impact on the motorneurons. Only 5% motorneurons reduced after radial nerves injured in 2/3, while other groups of the median nerves, radial nerves and ulnar nerves didn't decrease, including controls. 5. The quantity of the functional reserve of the median nerve, radial nerve and ulnar nerve is 1/3 of the whole trunk with well restoration.Conclusions 1. The brachial plexuses between rats and human being are very similar. The rats are the favorable experimental animal model on study of the brachial plexus of human being. 2. DiI is the satisfactory bi-direction nerve tracer, with supper axis specificity. It fit for the study on distribution of the nerve fiber. 3. As the donor nerves, the radial nerve is a potential one to provide more nerve fibers, while the median and ulnar nerve have the more degree of freedom to transportation and minor donor site for their longer trunks. 4. The lowest safe level of radial nerve is at the 80% of upper limbs, that the median nerve is 60%, and the ulnar nerve's is at meddle-down 1/3. 5. The quantity of the functional reserve of the median nerve, radial nerve and ulnar nerve is 1/3 of the whole trunk with well restoration. The nature of the functional reserve of peripheral nerves lies in the complicate network structure origin from proximal nerve fibers disperse and converge once and again.The peripheral nerves have an certain functional reserve just like other organs. The study showed that the donor nerves can compensation well after cut 1/3 nerve trunks, which provide the reliable evidence for solving the insufficiency of power nerves when treat brachial plexus avulsion and long section neurologic defects. The study surpassed the static observation to the bundle of peripheral nerves, convert to viviperception of tissue structure and function, which is a substitute to the impossible functional study on the nerves of human being.