C5 – C6 and upper truncal injury
An upper truncal injury with intact nerve roots is amenable to nerve graft repair. In C5-C6 root avulsion injury nerve transfers offer far superior results over tendon/ muscle transfers or shoulder arthrodesis . Nerve transfer between the distal spinal accessory nerve and the suprascapular nerve through the posterior approach restores useful range of shoulder abduction and external rotation. A simultaneous axillary nerve neurotization in the quadrilateral space further improves the range of shoulder abduction by reinnervating the deltoid muscle.
Elbow flexion is best achieved either by biceps reinnervation, or both biceps and brachialis reinnervation. In C5-C6 injuries intraplexal donor nerves provide better functional results than the extraplexal nerves (spinal accessory, phrenic, or intercostal nerves).The bifascicular nerve transfer between the ulnar and median nerves and the biceps and brachialis branches of the musculocutaneous nerve, has become a standard procedure in restoration of elbow flexion in C5- C6 root avulsion injuries. Sparing of single fascicle from the ulnar or median nerve does not result in any subjective deficit in hand function. Preoperative and postoperative evaluation of pinch strength, grip strength and two point discrimination at the pulp of little and index fingers usually remain unaltered .There is no added advantage in fascicular selection using a nerve stimulator while performing the fascicular nerve transfers.
C5 – C7 injury
In addition to the deficits observed in C5-C6 injuries these patients find difficulty in extension of elbow and wrist. Therefore triceps branch of radial nerve cannot be used for neurotization of axillary nerve. The lack of elbow extension leads to difficulty in putting the hand in space and reaching out on objects which affects prehensile functions. In these injuries reconstruction is similar to C5-C6 injuries, however long head triceps branch can be neurotized by 3rd & 4th intercostals nerves. When C6 root is available, it can be used to reconstruct the radial nerve. However it is important to note that delicate balance is required between elbow flexion and extension. If triceps becomes too powerful, it may adversely affect elbow flexion.
C5 – T1 injury
This is a severe injury characterized by flail upper limb. The first priority of reconstruction is elbow flexion followed by shoulder abduction. The hand reanimation is aimed at achieving protective sensation and some finger flexion. In these patients regaining some useful function for their daily activities is aimed at. In case of preganglionic injuries where no graftable root is available, nerve transfers is undertaken to achieve above reconstruction. A single stage reconstruction can be performed in 3 to 5 months post injury. The spinal accessory is used to neurotize suprascapular nerve and 3rd,4th,& 5th Intercostal nerves are used to neurotize musculocutaneous nerve. To regain protective sensation in hand and achieve finger flexion contralateral C7 (CC7) is used to neurotize median nerve using vascularised ulnar nerve graft.17 Later to achieve hand stability wrist arthrodesis and thumb fusion can be performed. Due to long graft and prolonged regeneration time the results of vascularised ulnar graft are unpredictable. Wang et al reported the use of direct cooptation of contralateral C7 root to injured lower trunk by a modified prespinal route. Out of 75 patients 35 also required humerus shortening by 3 to 4.5cms. In 47 patients they also used CC7 to neurotize musculocutanaous nerve through bridging antebrachial cutanous nerve arising from lower trunk. They reported successful outcomes in more than 50% of patients with greater than M3+ power in target muscles. Doi et al have described double free functioning muscle transfer using gracilis for achieving hand prehension, elbow flexion in total palsy. The details of this procedure are described in the succeeding paragraphs. They have reported that most of the patients were able to hold a can and could lift heavy objects. In post ganglionic injuries where graft-able roots are available, cable nerve grafts are used to reconstruct shoulder and elbow functions. Bertelli et al in their cohort of patients with total palsy 87% had graft-able roots. When C5 root is available, this root is used for neurotization of distal muscles. To achieve shoulder functions we transfer spinal accessory to suprascapular nerve and if C5 root is found graftable then it is neurotized to lateral cord using long cable grafts from sural nerve. When C6 is also found to be graftable it is used to neurotize the posterior cord using cable grafts. Our preference is therefore for shorter cable grafts.
C8 – T1 injury
These are uncommon injuries accounting for about 3% of all brachial plexus injuries.Hand functions are poor with preserved shoulder and elbow functions. The reconstruction aims to achieve prehension with protective sensation. Nerve transfers in form brachialis branch of musculocutaneous nerve to anterior interosseous nerve can be done to achieve grasp functions of hand.18 This however requires an interposition nerve graft. Alternatively brachialis branch can be transferred to posterior fascicular group of median nerve. The posterior fascicular group at brachialis group is composed of anterior interosseous nerve responsible for finger flexion. To restore finger flexion, motor branch to the brachioradialis muscle has been transferred to the anterior interosseous nerve in the management of lower plexus lesions.19
Prespinal route in contralateral C7
To reduce the distance to the target nerves, grafts connected with the contralateral nerve root, have been placed underneath the anterior scalene and longus colli muscles, and then passed through the retro-esophageal space to neurotize the recipient nerve.20
Infraclavicular injury
These are stretch injuries of brachial plexus and involve the peripheral nerves like axillary,musculocutaneous or radial nerves. Cord injuries may also occur in presence of severe trauma. They account for about 15% of all brachial plexus injuries. They are often associated with shoulder dislocation, or fractures of scapula and humerus and vascular injuries. Hence these injuries are challenging to deal with. Surgical exposure is by infraclavicular incision along the deltopectoral groove and pectoralis major is required to be detached from its insertion. The dissection is often tedious due to extensive scarring, previous surgeries and major vessels of upper limb in closed vicinity entrapped in dense fibrosis. Surgical options in their management include neurolysis, direct nerve repair and nerve grafting.
Secondary procedures in brachial plexus injury
A sizable number of patients fail to recover following primary nerve reconstruction. Also there is a group of patients who report more than a year after injury when nerve repair is not feasible. Such cases can be rehabilitated by secondary procedures such as tendon or muscle transfers, free functioning muscle transfers, osteotomies and arthrodesis.
Conclusion
In the management of brachial plexus injuries, an incorporation of micro surgical techniques in neurolysis, nerve repair, nerve grafting and nerve transfer has made possible to restore a functioning limb in many of the patients with brachial plexus injuries, which was considered a difficult or an impossible task just two decades back. An early repair within 6 months of injury is important for a successful outcome. Patients reporting late may be benefited with secondary muscle and skeletal procedures.
