To The Editor:
We appreciate that, among the surgical treatments for patients who have sustained complete or almost complete avulsion of the brachial plexus, the one described by Doi et al. in their article "Restoration of Prehension with the Double Free Muscle Technique Following Complete Avulsion of the Brachial Plexus. Indications and Long-Term Results" (2000;82:652-66), is the best. They use the spinal accessory nerve as a donor nerve to reinnervate the transferred gracilis muscle at the first stage of the operation. We performed the double free muscle technique in twelve patients, but in four of them the spinal accessory nerve did not function satisfactorily, as a result of the primary injury, and therefore was unavailable. In three of those four patients, we used the trapezius branch of the cervical plexus as our modification of this operation.
This double muscle technique involves a two-stage reconstruction. In the first operation, free muscle is transferred to restore elbow flexion and finger extension. The spinal accessory nerve is used to reinnervate the transferred muscle. In the second operation, muscle is transferred to restore finger flexion, with use of the fifth and sixth intercostal nerves to reinnervate the transferred muscle. We tried to use the spinal accessory nerve as the donor nerve, according to the method of Doi et al. However, when powerful contraction of the trapezius muscle was not observed on direct stimulation of the spinal accessory nerve with an electrostimulator, we undermined beneath the trapezius muscle and exposed the trapezius branch of the cervical plexus. Then we compared the contraction power evoked by the trapezius branch of the cervical plexus with that evoked by the spinal accessory nerve to select the superior donor nerve. As we stated, in three of four patients with unsatisfactory function of the spinal accessory nerve, the trapezius branch of the cervical plexus was used as the donor. (In the fourth patient, who had virtually complete damage of both the spinal accessory nerve and the trapezius branch of the cervical plexus, nerve-grafting of the lacerated spinal accessory nerve was performed.) The time interval until reinnervation was considered to be the number of days or months after the surgery until muscle contraction was recognized as grade 1 on manual muscle testing. The final contraction power of the transferred muscle was evaluated two years after the last operation. The average time interval (ninety-eight days) and the final grade on manual muscle testing (3.6) after use of the trapezius branch of the cervical plexus were both far better than those after use of the intercostal nerves (8.4 months and 2.4, respectively). Although these results cannot be analyzed statistically because of the small number of patients, it can be safely said that the trapezius branch of the cervical plexus appears to be superior to the intercostal nerves and equal to the spinal accessory nerve with regard to the time to reinnervation. Doi et al. reported the same results but suggested that the final muscle contraction powers were not significantly different between the spinal accessory nerve and the intercostal nerve.
Other donor nerves that have been used are the phrenic nerve and the contralateral seventh cervical nerve
1,2 . If the damage of the spinal accessory nerve can be diagnosed precisely before the first operation, and if prefabricated nerve-grafting to those intact nerves is possible, those strategies are also available. When the spinal accessory nerve cannot be used, we recommend that the trapezius branch of the cervical plexus be selected as the donor nerve, and, if possible, the injured spinal accessory nerve be repaired at the same time for future additional reconstruction of shoulder function.
K. Doi, Y. Hattori, and M. Watanabe reply:
We partially agree with the proposal, by Dr. Kusakabe et al., to use the trapezius branch of the cervical plexus as the donor nerve.
It is well known that the trapezius muscle is innervated by the spinal accessory nerve and the trapezius branch of the cervical plexus. However, the location of the trapezius branch of the cervical plexus as a second source of trapezius innervation is variable. In cadaver dissections, it is usually situated under the sternocleidomastoid and thus proximal to the usual level of the spinal accessory nerve
3 ; however, we found that the trapezius branch of the cervical plexus connects to the spinal accessory nerve distal to the branches to the proximal part of the trapezius in most cases. We prefer to divide the spinal accessory nerve proximally, where the branch of the cervical plexus joins, to preserve function of not only the proximal part of the trapezius but also the middle and distal parts. Our clinical experience also has shown that, in two-thirds of patients, after transfer of the terminal branch of the spinal accessory nerve distal to the connection with the cervical plexus, the middle and distal parts of the trapezius were not completely denervated electromyographically
4 . We have no experience in using the trapezius branch of the cervical plexus as a donor nerve for the first free muscle transplant; however, it may be another option when the spinal accessory nerve is injured proximally. It should be noted, though, that in this situation total trapezius paralysis prevents the distal prehensile function restored by the double free muscle technique even if the muscle transplant is successfully reinnervated by the trapezius branch of the cervical plexus. We do not recommend the use of the trapezius branch of the cervical plexus as a donor nerve for the first muscle transplant when the spinal accessory nerve is injured since prehensile function without shoulder stability is useless in daily activities even if the patient can obtain minimal voluntary finger motion.
We prefer to use the trapezius branch of the cervical plexus as a donor nerve for neurotization to the suprascapular or long thoracic nerve when the spinal accessory nerve is not injured and is used as a donor nerve for the first free muscle transplant.