Anatomic Study Of Posterior Approach For Transfer Of The Spinal Accessory Nerve To The Suprascapular Nerve

Objective:anatomical study of trapezius muscle innervations in order to find the best point for transfer of the spinal accessory nerve to the suprascapular nerve.Method:observation of right & left trapezius muscle innervations in ten cadavers.Study the course and branches of accessory nerve within the trapezius muscle.Resection and cross-sectional biopsy of accessory and suprascapular nerves at different levels.Counting and comparing the number of nerve fibers at different levels in both nerves.Result:the accessory nerve enters trapezius muscle within the deep fascia and run posterior just 2-3cm above the clavicle.At the level of the midpoint of the spine of the scapula 3-4cm above and anterior,it unites with the cervical branch of the cervical plexus,then crosses medial to the spine of the scapula with straight course down to the lower trapezius.Accessory nerve gives 2-4 branches to the upper part of the trapezius muscle before union and gives 4-7 branches to the lower part after union with the cervical branch.The number of nerve fibers in cross section at point A(just entering the muscle)was 1245±46,in point B (just before union with cervical branch)was 830±36 and in point C(posterior approach incision)was 1074 C±38.Conclusion:we recommend Posterior approach of accessory nerve transfer as the anatomy is constant;Operation is simple and does not affect the upper trapezius muscle innervations.Also it gives us a full use of the cervical branch and shortens the nerve regeneration.The part of accessory nerve after union and just above the spine of the scapula is the best point for transfer as the branches are less and loss in number of nerve fibers is minimal.