Type of brachial plexus injury	Nerve axon donor	Common targets
Any injury with neuroma-in-continuity conducting NAP	Neurolysis
Any injury with nerve rupture or post-ganglionic neuromas not conducting NAP and good proximal nerves (preserved SSEP and MEP)	Direct repair or repair with graft if possible
	C5 nerve	Shoulder stability, abduction, and external rotation: Suprascapular nerve Axillary nerve Posterior division of UT
	C6 nerve	Elbow flexion: Anterior division of UT Musculocutaneous nerve
	C7 nerve	Elbow extension: Posterior division of MT Radial nerve
Complete C5–T1 panplexus injury	Nerve transfers: XI	Suprascapular nerve Musculocutaneous nerve Free functioning muscle
	Motor ICN	Musculocuatenous nerve Motor branch to the biceps
	Sensory ICN	Lateral cord contribution to the median nerve
	Other potential donors: Phrenic nerve Contralateral C7 nerve
C5–C6–C7 and C5–C6 Additional options	Ulnar nerve fascicle(s)	Motor branch to the biceps
C5–C6–C7 and C5–C6 Additional options	Median nerve fascicle(s)	Motor branch to the brachialis Motor branch to the biceps
C5–C6 Additional options	Triceps motor branches from radial nerve	Axillary nerve proper Anterior division of axillary nerve
C5–C6 Additional options	Other potential donors: Medial pectoral nerves Ipsilateral C7 nerve
C8–T1 Options	Tendon transfers Selective arthrodesis of joints Free functioning muscle transfer

Abbreviations: ICN= intercostals nerve, MEP=motor-evoked potential, MT=middle trunk, NAP= nerve action potential, SSEP=somato-sensory-evoked potential, UT=upper trunk.

Complete (pan) brachial plexus injury

In patients with complete brachial plexus injury, useful recovery may still be obtained despite obvious limitations in the availability of functional donor nerves. If no proximal nerve is available, a common strategy consists of transferring the spinal accessory nerve to the suprascapular nerve (for shoulder stability), motor intercostal nerves to the musculocutaneous nerve or to the motor branch of the biceps (for elbow flexion), and sensory intercostals nerves to the lateral cord contribution of median nerve (for hand sensibility). When proximal nerves are available, a reconstructive strategy using multiple nerve transfers and nerve grafts may allow the possibility of regaining additional useful functions, including even rudimentary hand function. Additional donors have also been described, such as the phrenic nerve and contralateral C7 nerve. Our group stopped using the phrenic nerve, in view of our population of patients (often overweight and at risk to develop cardio-respiratory disease in their lifetime) and of the occurrence of respiratory function compromise in one patient. After review of our results from hemi-contralateral C7 nerve transfer for hand function, we now seldom choose this approach to regain hand function because of the poor functional grasp that was obtained.¹ However, we currently often neurotize a free functioning gracilis muscle for elbow flexion in the acute stage to increase the chances of achieving adequate elbow flexion. If the triceps can be reinnervated (such as by nerve grafts from C7 or spinal accessory nerve), we consider using a free functioning muscle for both elbow flexion and finger flexion by prolonging the distal gracilis tendon to the flexor digitorum profundus and flexor pollicis longus tendons.

C5–C6 brachial plexus injury

When preganglionic injuries of the C5 and C6 nerves are present, several nerve transfer options exist to restore shoulder stability and elbow flexion. Potential donor nerves include the spinal accessory nerve, the triceps motor branches of the radial nerve,^2,³ the medial pectoral nerves, the ulnar or median nerve,⁴^–⁸ the intercostals nerves, the phrenic nerve, the ipsilateral⁹ and the contralateral C7 root. A common treatment approach includes the transfer of ulnar nerve fascicle(s) to the biceps motor branch of the musculocutaneous nerve to restore elbow flexion (Oberlin’s transfer), and a spinal accessory nerve transfer to the suprascapular nerve. The Oberlin’s transfer, with its good results, is now the procedure of choice for biceps reinnervation in preference to intercostal or spinal accessory nerve transfers.¹⁰ In our group, we attempt dual reinnervation when possible of both the shoulder (supraspinatus and deltoid) and elbow (biceps and brachialis muscles). The deltoid can be reinnervated using a triceps motor branch of the radial nerve to the axillary nerve and the brachialis muscle can be reinnervated with a fascicle from the median nerve.

In patients with postganglionic ruptures or postganglionic neuromas not conducting nerve action potentials, both nerve grafting and nerve transfers can be done and there is controversy as to which approach is preferable. We usually prefer to use nerve grafting from C5 for shoulder function if the repair is done early and the proximal nerve has a good macroscopic appearance as well as good somato-sensory and motor-evoked potentials intra-operatively; we typically use double fascicular transfer for elbow flexion. If the exploration and repair is done late, or there are uncertainties about the integrity of the proximal nerves, then we prefer to perform double nerve transfers for shoulder function and elbow flexion.

C5–C6–C7 brachial plexus injury

When C7 is involved and the triceps muscle is weak, the triceps motor branch to axillary nerve transfer cannot be done. In that situation, the same strategy as described for the C5–C6 brachial plexus injury can be used, but intercostals nerves may be used to reinnervate the axillary nerve if necessary. If the wrist and finger extension are affected, we generally reinnervate the triceps muscle with nerve grafts or nerve transfers and the distal function is addressed by tendon transfers either simultaneously or at a subsequent surgery.

C8–T1 brachial plexus injury

We treat lower trunk brachial plexus injuries by a combination of tendon transfers, selective arthrodesis of joints, and/or free functioning muscle transfer. The approaches to restore hand function are described in greater detail in Tu and Chung’s chapter on hand reconstruction. Tendon transfers, such as extensor carpi radialis longus to flexor digitorum profundus and brachioradialis to flexor pollicis longus, can be performed to restore finger flexion and pinch. Selective arthrodesis of the interphalangeal and carpometacarpal joint of the thumb can also improve both grasp and pinch. As the results of nerve repair are poor in lower trunk injuries because of the distance and time for reinnervation, we generally do not attempt nerve surgery in these patients. Others have suggested distal nerve transfers using the supinator motor branch to the posterior interosseous nerve, the brachialis branch of musculocutaneous nerve to the anterior interosseous median nerve fascicles, or the radial nerve branch to the extensor carpi radialis brevis muscle to the anterior interosseous nerve.¹¹^–¹⁵ At present, when good tendon transfer and arthrodesis options exist, we prefer these approaches.

Pre-procedural/therapeutic considerations

Before attempting any reconstructive procedure for patients with brachial plexus injuries, a multidisciplinary evaluation is necessary. This multidisciplinary approach should be used from the time of the first evaluation, intraoperatively, as well as in the immediate and long-term post-operative period. The multidisciplinary team consists of a neurologist, a neurosurgeon, an orthopedist, and/or a plastic surgeon, a pain specialist, a physiotherapist, and an occupational therapist.

The importance of the initial evaluation, including a detailed history and physical examination (neurologic, musculoskeletal and vascular), as well as review of the nerve conduction, electromyographic, and imaging studies was discussed in previous chapters and will not be reviewed here. However, a few particular pre-operative considerations are specific to our reconstructive approaches and need to be discussed.

When intercostal nerve transfers are considered, dynamic (inspiratory and expiratory) chest radiography is useful to assess phrenic nerve function and prior rib fractures. If the patient has a phrenic nerve dysfunction and/or a history of rib fractures, pneumothorax, hemothorax, pulmonary contusions, or respiratory compromise, pulmonary function tests (PFT) should be considered to better characterize the pulmonary function. These evaluations, with an assessment by a pulmonologist if necessary, will help determine if intercostal nerves may be utilized as donor nerves for transfers. Generally, even if a phrenic nerve dysfunction is present, the patient will tolerate up to 4 or 5 intercostal nerve transfers, unless his pre-operative PFT are very low (i.e. less than 40% of expected, but no definite criteria exist). The patient’s body habitus and smoking habits should also be taken into consideration before the use of intercostal nerves, especially in the context of a phrenic nerve dysfunction. The presence of rib fractures does not preclude the use of intercostal nerves. In our experience, there is a 10% risk that the intercostal nerve at the level of the rib fracture will be non-functional (i.e. will not stimulate) and will not be usable as a donor. It is important to counsel patients appropriately and make them aware of the possibility that the nerves may not be functional; this is especially important if a patient had multiple rib fractures at the time of trauma. Intra-operatively, direct stimulation is the usual definitive method to assess function of the intercostal nerves.

When the spinal accessory nerve is considered for transfer, its function should be evaluated pre-operatively. The function can be assessed clinically by evaluating trapezius muscle function (shoulder shrug), comparing its strength to the opposite side. However, since this method is not sensitive, electromyographic study of the trapezius demonstrating normal motor unit potentials and absence of abnormal insertional activity is useful in documenting an intact spinal accessory nerve. If the spinal accessory nerve has been injured at the time of the trauma, it may still be explored and utilized if there is good stimulation intraoperatively, knowing that the nerve may not be completely normal.

Not all patients are appropriate candidates for free functional (gracilis) muscle transfer (FFMT). A few particular pre-operative considerations are specific to this particular reconstructive approach and need to be discussed. First, a viable arterial and venous supply must be present. Second, an expendable motor nerve must be present near the transferred muscle’s neurovascular pedicle to reinnervate the transferred muscle. The third and fourth intercostal motor nerves and the spinal accessory nerves are usually good candidates. The patients considered for FFMT must understand the inherent risks, including flap loss, and the expected outcomes.¹⁶ They must be prepared to undergo a major operation with hospitalization and extensive rehabilitation and understand the goals of the surgery.

Supple joints are preferable before function is restored. If full passive range of motion is lacking, therapy or capsular release may be indicated. When restoring elbow flexion, especially if a FFMT is considered, shoulder stability should be discussed. Although shoulder stability is not a pre-requisite, if the shoulder is subluxed, a FFMT anchored to the clavicle and acromion will initially use some of its force to reduce the subluxed shoulder; this will in turn diminished elbow flexion strength of the transferred free muscle.

The upper extremity recipient bed for the transferred muscle must provide adequate skin coverage and ideally be free of adherent scar, to allow for muscle and tendon gliding. However, this may not always be possible in cases of brachial plexus injury. If the skin is significantly scarred, it may be difficult to cover the muscle transfer. Transferring a skin paddle with the muscle may help, but this is reliable only proximally for the gracilis myocutaneous flap ¹⁷ and coverage of the distal end of the muscle and tendon may remain an issue. Using the muscle transfer for the “dual purpose” of providing elbow flexion and coverage of exposed structures or hardware is not recommended as it will lead to inevitable scarring and result in poor outcomes.

Another important consideration is the assessment of the vasculature to the injured upper extremity, especially when a FFMT is considered. In these patients, especially when the first rib has been fractured, the axillary and subclavian vessels may have sustained an injury.^18,¹⁹ In the authors’ experience, a normal peripheral pulse does not preclude vascular injury, especially in the major branches. Therefore, we generally evaluate the vasculature using MR angiography (MRA). Special attention is given to the thoracoacromial trunk, our preferred source of arterial supply for the FFMT. Other options to formally evaluate the vasculature include CT angiography or conventional angiography. Any of these vascular studies will also assess post-traumatic stenosis and the patency of a previous vascular repair or reconstruction. In cases in which the thoracoacromial trunk is not intact, alternative options may be explored for the vascular anastomoses, including vein graft, arteriovenous loop preparation, and end-to-side anastomosis into the axillary artery.²⁰