Experimental Study On Reimplantation Of Ventral Root Into The Spinal Cord After Brachial Plexus Avulsion

Brachial plexus roots avulsion is one of the most severe injuries in the upper limb, and is also one of the most challenging one to treat among all peripheral nerve injuries. During the last 3 decades of the 20th century, some progressions have been made in the surgical treatment of such condition. To improve the function of the paralyzed upper limb, many surgeons adopt the "nerve transposition" and "muscle transplant reconstruction" method to recover the shoulder elevation, elbow flexion, wrist flexion and extension, as well as gross grasping of hand. However, due to the proportion of the number of nerve fibers suitable for transposition in the motor area to that in the receiving area is only 1 to 10, it is difficult to find enough nerve fiber for the transposition. Recognizing this problem, nerve root reimplantation, a repairment in the spinal cord level, is getting increasing interest. Researches are being done on implantation of the avulsed ventral root to the spinal cord so and its effect on recovering limb functions.Object: To investigate the mechanisms of secondary degeneration of motor neurons in the ventral horn of the spinal cord after brachial plexus roots avulsion, to observe the survival effect and reaction mechanisms of motor neurons after reimplantation of the avulsed root into the spinal cord. To observe the survival and differentiation in the spinal cord.Materials and methods:1. Thirty adult male Wistar rats were randomly devided into the experimental group and the control group,with 15 each. The surgical procedures were carried outwith the animals under general anesthesia using Chloral Hydrate. Laminectomy of C4-C6 was performed via a posterior approach. The ventral and dorsal roots of C5-C6 were both avulsed from the spinal cord outside the dura mater and within the vertebral canal.2. The ventral root of C6 was reimplanted into the ventral horn under microscope. The dorsal root was left unattended. The ventral and dorsal roots of C5 were placed inside the nearby muscles. For the control group, the ventral and dorsal roots of both C5 and C6 were placed inside the nearby muscles.3. At 2, 4, 6, 8, 12 weeks postoperatively, specimen was obtained from the spinal cord and nerve root at C6 level under deeply general anaesthesia.The C6 spinal cord was stained with HE. The change of number and morphology of motor neurons were observed on HE-stained sections. The C6 spinal nerve root was stained with silver nitrate, and the regeneration of nerve fiber was observed.Results:1. All animals displayed unilateral upper limb paralysis postoperatively and other limbs were not affected.2. At each time point postoperatively, the HE-stained transverse sections showed: the number of motor neurons decreased significantly with soma swollen and atrophied. At 6 weeks postoperatively, the number of lost motor neurons in the control group and experimental group were 69.4% and 51.3%. At 12 weeks, the lost reached 79.6% and 57.5% respectively. The survival rate of motor neurons in the experimental group is higher than the control group at all time points.3. In the experimental group, the silver nitrate stained specimen from the C6 nerve4root showed regeneration of the motor neurons in the ventral horn into the reimplanted nerve root through axon, and the number of myelinated nerve fibers is higher than the control group.Conclusions:1. Degeneration of motor neurons will take place in the ventral horn of the spinal cord after brachial plexus roots avulsion.2. Through reimplantation of the avulsed ventral nerve root into the ventral horn, degeneration of the motor neurons in the ventral horn can be reduced.3. After reimplantation of avulsed nerve root, there is axonal regrowth of motor neurons into the spinal nerve root and regeneration of the myelinated nerve fiber also appears.