In C5,C6 root avulsions the proximal root stumps are not available for grafting, hence repair is based on nerve transfer or neurotization. Restoration of elbow flexion takes priority in functional reconstruction, followed by shoulder abduction and external rotation. Reinnervation of musculocutaneous nerve has been achieved with transfer of a variety of donor nerves; the spinal accessory nerve, the medial pectoral nerve, the phrenic nerve, the thoracodorsal nerve and the intercostals nerves. The functional results have been unpredictable with the use of phrenic nerve, medial pectoral nerve and the thoracodorsal nerve. Use of distal end of spinal accessory nerve requires long nerve graft and results are far from satisfactory. Multiple donor nerves are required while using the intercostals nerves.
Selective neurotization of biceps and brachialis muscles with part of ulnar and median nerves have produced consistently good functional results without notable impairment of hand function.
Transfer of the spinal accessory nerve to the suprascapular nerve produces an average of 45 degrees of shoulder abduction (range from less than 20 to 80 degrees). Recently many surgeons have recommended nerve transfers to both the suprascapular and axillary nerves to achieve better results. Transfer of motor branch to long head of triceps to anterior branch of axillary nerve produces minimal functional loss and is compensated easily by the remaining of the triceps and the teres muscle group.
C5 and C6 palsies occur in 15 to 20 percent of supraclavicular plexus injuries.Repair of these injuries offer good prognosis because the hand functions are preserved. If the injury is in the roots in the scalenic area or upper trunk, there is a good possibility for nerve repair with a satisfactory result. In C5 and C6 root avulsions, nerve repair is not possible and nerve
transfers offer far superior results over tendon/ muscle transfers or shoulder arthrodesis. It is well accepted that the two main priorities in nerve transfers are the restoration of elbow flexion and shoulder abduction. Elbow flexion has been achieved with many donor nerves including the intercostal nerves, medial pectoral nerve, phrenic nerve, thoracodorsal nerve, spinal accessory nerve and recently introduced Oberlin transfer. An intercostal nerve contains no more than 500 motor fibers, hence at least two or three intercostals nerves (T3, T4 and T5) are coapted with the motor component of musculocutaneous nerve. Some surgeons do not recommend intercostals to musculocutaneous transfer as the surgery is challenging and time consuming, results are not consistent, and life threatening complications have been observed.
Transfer of medial pectoral nerve to the musculocutaneous nerve is one of the most controversial procedures. In 1948, Lurje described the use of this nerve as a donor in patients with Erb’s palsy. Thereafter only a few reports of the use of this nerve transfer were published. Some authors do not recommend this type of nerve transfer at all. Chuang et al and Gu et al have popularized the transfer of phrenic nerve to musculocutaneous nerve (either directly or with a sural nerve graft). This procedure again has not gained wide acceptance amongst the western surgeons as it sacrifices an important motor nerve, contraindicated in children and can not be combined with simultaneous intercostals nerve transfer.
The spinal accessory nerve has the disadvantage of requiring a long nerve graft to reach the musculocutaneous nerve.
Transfer of a single fascicle of ulnar nerve to the motor branch of biceps and a fascicle median to the brachialis have produced the most promising results as there is no wastage of any donor nerve fibers to the sensory part of musculocutaneous nerve. Since the nerve transfer is performed close to
the target muscle, the return of function is faster. This technique requires no special re-education of the muscle. Sparing of 1 or 2 fascicle form the ulnar and median nerves does not result in any subjective deficit of hand function. Preoperative and postoperative evaluation of pinch strength, grip strength and two point discrimination at the pulp of little and index fingers remain unaltered.
Shoulder stability and abduction can be restored by arthrodesis, muscle tendon transfer and nerve transfers. Shoulder arthrodesis yields a poor range of motion. It is difficult to achieve satisfactory abduction by muscle/ tendon transfers with use of trapezius, levater scapulae, sternocleidomastoid or latissimus dorsi muscles. Nerve transfer, however, provides good range of shoulder abduction and stability. Transfer of distal spinal accessory nerve to the suprascapular nerve restores an average of 450 of abduction and some external rotation by reactivating the supraspinatous and infraspinatous muscles. A simultaneous transfer of suprascapular nerve and axillary nerve yields much better results when adequate donors are available. Axillary nerve neurotization can be performed through an anterior approach using phrenic nerve, distal spinal accessory nerve, intercostal nerves or medial pectoral nerve as donor nerves. This approach not only requires nerve grafts but also results in dilution of nerve fibers entering the deltoid muscle. A posterior approach allows the transfer of nerve to the long head of triceps (which contains mainly motor fibers) to the anterior branch of axillary nerve which innervates the anterior and middle deltoid muscle. This transfer avoids the misdirection of the regenerated axons in to the cutaneous branch and teres minor. The functional loss is minimal and is compensated by remaining 2 heads of triceps and the teres muscle group.
CONCLUSION
Selective neurotizations closer to the motor end plates allow an early return of function. The return of power is much superior to the other conventional methods of nerve transfers. The functional loss is minimal. Multiple nerve transfers are preferred in the management of C5,C6 root avulsion injuries.
