PRIMARY NERVE GRAFTING-

Severe crush injuries and nerve surgeries for tumor ablation requires nerve repair leading to approximation with either tension or gap. Such situations entail primary nerve grafting as an option for nerve repair.

SOURCES-

• Sural nerve- harvested from the lateral aspect of the leg is one of the most common sources of nerve graft with approximately 30-40cms length may be harvested.
• Lateral antebrachial cutaneous nerve
• Medial antebrachial cutaneous nerve are some other sources.

Pre-Requisites for Nerve Grafting- Skeletal Stability

• Adequate soft tissue cover
• A healthy wound bed
• Timing of repair- too late a repair may sometimes not yield beneficial results especially if long segment recovery would extend beyond 1year.

PROCEDURE-

The transected nerve is prepared and crushed ends prepared till healthy. The length of graft assessed with respect to length of inter-bridging segment needed and number of cables required with respect to the thickness of the nerve to be repaired. Adequate segment of nerve harvested allowing repair without tension. The repair is done under microscope magnification(preferred ) or under loupe magnification.

Disadvantages-

1. Donor site Scarring
2. Donor site sensory loss (Patient needs to be educated to sensitize and prevent future injuries)
3. Two Co-aptation sites need to crossed by the growing axonal outgrowths and thus two sitesof latency. Hence, nerve transfer may be considered a better option in long segment defects.

NERVE TRANSFERS-

Nerve transfers are indicated in situations where

1. Nerve roots have been avulsed from the spinal cord (pre-ganglionic injury) or when the proximal nerve is otherwise unavailable for repair using nerve grafts.
2. Long nerve graft is required (as results are poor)
3. Long distance between injury site and motor end plates (long recovery time)
4. Late presentation.
   There is increasing preference for using nerve transfers for re-innervation even when primary nerve graft may be possible. An important advantage of nerve transfer over primary nerve grafting is that in nerve grafting, the regenerating fibres must cross two anastomosis sites and the second or distal site is reached much later with more fibrosis and scarring at surgical site and hence, longer recovery or failure in cases of long grafts.

Nerve transfers may be-

INTRAPLEXAL REPAIR:

Repair of injured nerve utilizing nerve grafts within the brachial plexus. Nerve branches supplying accessory or inconsequential function, without compromising hand function, may be harvested from the ipsilateral brachial plexus. It is applicable in non-global root avulsions wherein atleast one spinal nerve with small rupture injury is available for transfer (not to its original but to other more important nerve roots within the plexus). Most common for upper brachial plexus palsy is the Oberlin repair i. e. transferring a part of the ulnar nerve to the branch to the biceps (Oberlin 1) and transferring a part of the median nerve to the branch to the brachialis (Oberlin 2).

EXTRAPLEXAL REPAIR-

Includes utilizing nerve grafts outside the brachial plexus, i.e. from adjacent areas as neck. Functionally less important nerves are harvested. Eg- intercostal nerves may be harvested and transferred to axillary nerves. Accessory nerves may be used for repair of suprascapular nerves. Usually aimed at motor re-innervation though sometimes used for extraplexual sensory transfer for providing sensation to a paralytic hand to prevent ulceration and injuries.

DISTAL NERVE TRANSFERS:

distal nerve transfer is a procedure that involves direct coaptation of nerve end to a site much more close to the neurovascular junction (distal) away from the brachial plexus to facilitate faster recovery of motor neurons and muscle function.

RISKS-

1. Donor site morbidity
2. Skin grafting
3. Muscle co-contraction
4. Long duration of recovery
5. Patient training and education