Treatment of Severe Brachial Plexus Injuries
Trauma to the upper arm during accidents can result in avulsion (complete tear) of the brachial plexus. In this study, the use of nerve transfers is explored for these injuries in six patients.
The brachial plexus is a group of nerves that start at the spinal cord in the neck area. At this level, the nerves are called spinal nerve roots. The nerve roots branch out and form the three main nerves to the arm. All six patients experienced brachial plexus injuries from motorcycle, skiing, car, or agricultural accidents.
Most of the patients came to the study clinic some time (months to years) after the original injury. They were examined carefully with a wide range of tests and measures. Range of motion, muscle strength, and function were evaluated. Photographs and videos were taken to document their baseline status at the start of treatment. All measurements were compared with average normal values for each area.
Sometimes primary muscles responsible for a movement weren't working. The patients developed muscle substitution (one muscle doing the job of another). The presence of any muscle substitutions was noted. Shoulder stability was also assessed.
All patients had surgery to find out how badly the brachial plexus was injured. Intraoperative electrical stimulation was used to test the location and status of the nerves. The main focus was on the use of the pectoral nerve. Nerve grafting and nerve transfers were used to restore motor function of the upper extremity.
The surgical technique was described in detail by the authors. Exact locations of the transfers and grafts were discussed. In the basic procedure, the pectoral nerve was divided on one side and then surgically attached to the torn nerve.
Pectoral nerves are used for several reasons. The nerve is broken down into several parts or segments. Usually, not all segments are destroyed. So there is some part of the pectoral nerves that are still working. At the same time, there is segmental innervation of the pectoralis major (chest) muscle. Segmental innervation means that more than one nerve controls the muscle. If one part of the nerve plexus is torn, another part can be used to signal the muscle to contract.
The pectoral nerves also have a large number of motor fibers. This increases the chance of success for reinnervation of the affected muscles.
The nerves are close enough to the area of damage that re-routing them isn't too difficult. The closer the nerve is placed to the muscle target, the faster the recovery will be. This is important because if a nerve pathway isn't used, and the muscle doesn't contract, both soft tissues start to atrophy (waste away).
But with the right placement of nerve graft or nerve transfer, new nerve fibers will grow back to the place where the nerve was damaged. The placement of nerve transfers and grafts for brachial plexus injuries depends on where the nerve root was ruptured and how severe the tear was.
Results from these six patients with their seven pectoral nerve transfers were reported as good-to-excellent for six of the seven nerve transfers. The patients were able to use the donor nerve to contract the muscles. Electromyographic studies and strength of muscle contraction were used as measures of success. Elbow, forearm, and wrist motion was also compared from before surgery to after the procedure.
The authors report that this type of complex brachial plexus reconstruction may be needed when direct repair of torn nerve roots can't be done. But the results aren't guaranteed. If the distance between the donor nerve and the muscle it is trying to reach is too great, regeneration can take a long time.
If the new nerve reaches the target muscle, there may not be enough motor fibers to get a good, strong muscle contraction. Even if the muscle is reinnervated, it doesn't always function normally. And there is a chance that function of the pectoralis major muscle will be impaired. It's a gamble that with multiple nerves supplying this muscle, if muscle function is lost, it will only be partial -- not enough to affect how the arm moves.
In summary, pectoral nerves are dependable sources of nerve grafts for severe brachial plexus injuries. This type of reconstruction is most successful when used on young individuals without a long delay between injury and surgery.
Theresa Stockinger, MD, et al. Clinical Application of Pectoral Nerve Transfers in the Treatment of Traumatic Brachial Plexus Injuries. In The Journal of Hand Surgery. September 2008. Vol. 33A. No. 7. Pp. 1100-1107.
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