Potential Mechanism for Some Postoperative C5 Palsies: An Anatomical Study

Anatomical Study.

Determine if shoulder depression (eg, taping the shoulders) might result in C5 nerve traction and subsequent injury.

Postoperative C5 nerve palsy is a recognized entity that is still often enigmatic. Inferior shoulder depression is usually employed to assist with surgical visualization during cervical spine procedures.

In the supine position, 10 adult fresh frozen human cadavers underwent dissection of the spinal cord and its adjacent dorsal, ventral roots, and spinal nerves from C4 to T1. In the supine position, the head was rotated ipsilaterally, contralaterally, and in lateral flexion. The shoulder was elevated, retracted, protracted, and depressed all with direct observation of nerve roots, intradural ventral/dorsal rootlets, or the spinal cord. The effects of these movements upon the cervical nerve rootlets were measured.

The greatest displacement of nervous tissue was generated by shoulder depression and occurred primarily at the intradural rootlet level. The nerve rootlets that underwent the greatest average displacement were found at C5, with a decreasing gradient to C7 and no gross motion at C8 or T1. With maximal shoulder depression, C5-C7 rootlet tension produced cord movement to the ipsilateral side, touching the dura mater covering the lateral vertebral column with the C5 nerve root moving farthest.

Shoulder depression is often used during cervical spine surgery. In cadavers, shoulder depression causes significant tension and displacement of the C5 nerve rootlets, and in the extreme, cord displacement to the ipsilateral side. This could be a mechanism for injury, putting patients at greater risk for postoperative C5 palsy.

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