End-to-Side Nerve Suture
End-to-side nerve suture (ETSNS) is now accepted as a practical option to restore peripheral nerve function. Many experiments were done on “lower” animals (e.g., rats, rabbits), but it was only in 1993 that “higher” animals (e.g., Chacma baboons, Papua ursinus) were used as experimental models.1 The results conclusively showed that an intact nerve (“donor nerve”) has the potential to sprout laterally, forming side branches from existing axons, to fill an attached nerve (“recipient nerve”). Even so, much skepticism existed among leading peripheral nerve experts. The results were so convincing that we embarked on the first large series of ETSNS in humans.2–5 Presently, many publications (experimental and clinical) confirm the ability of nerves to share axons with other nerves by forming buds, which grow down recipient nerves to the target organs (e.g., skin and muscles).6,7 Many variations of ETSNS techniques are presented in the literature6–10 to adapt or to overcome unusual nerve lesions. ETSNS does not aim to replace end-to-end nerve suture or even gap bridging with nerve grafts or artificial conduits. ETSNS is an alternative method and may be the only alternative to restore function in a peripheral nerve under such conditions as brachial plexus root avulsion,11 large segmental nerve loss, and complex injuries (e.g., a compromised wound), and when nerve reconstruction is ill-advised (e.g., potential sepsis, severe scar tissue).8,9 ETSNS is then done more distally in healthy, normal tissue.4,6 Good results are achieved in pure motor nerves (e.g., neurotizing the musculocutaneous nerve for biceps function)12 and pure sensory reinnervation (e.g., digital nerves).
Examples of indications for ETSNS include the following:
In high ulnar nerve lesion, suturing the distal stump of the ulnar nerve at the wrist in an end-to-side fashion to the median nerve at the wrist (the target organs are closer, and axonal down growth fatigue is eliminated) ( Fig. 15.2 )4,5
As a simpler solution when nerve grafts are needed
In combination lesions with tissue loss (e.g., median and ulnar nerve in the forearm); a nerve graft is taken from the ulnar nerve, interposed in the median nerve gap, followed by an ETSNS of ulnar nerve into the graft ( Fig. 15.12 )4
Suturing the axillary nerve to the posterior cord of the brachial plexus to reinnervate the deltoid muscle ( Fig. 15.3 )
Very few absolute contraindications exist, because by doing an ETSNS nothing is lost (i.e., the worst scenario is that no functional recovery is seen).
A relative contraindication may be using a weak or suboptimal nerve as a donor.
Although many variations exist in performing the ETSNS, the following description should serve as a standard technique using 2.5–3× magnification:
Step 1: Identify intact functioning nerve, root, or cord.
Step 2: Choose a suitable area for the operation (e.g., undamaged surrounding soft tissue, away from joints).
Step 3: Skin incision is a lazy “S” shape. The proximal leg of the “S” lies over the donor nerve, the middle part over the planned suture site, and the distal leg over the recipient nerve.
Step 4: The recipient nerve is dissected free and the stump prepared for the suture. Take care to prepare a clean undamaged nerve end, which will be sutured to the side of the donor nerve ( Figs. 15.4 and 15.5 ).
Step 5: The recipient nerve is now swung toward the donor nerve, making sure that it will not impinge on any structures, will not kink, and will be free of any tension when attached to the donor nerve ( Fig. 15.6 ).
Step 6: The donor nerve is carefully dissected free for about 2–3 cm on the side where the suture will take place.
Step 7: A longitudinal incision is very carefully made on the side of the donor nerve (i.e., on the same plane as the approaching recipient nerve). The incision should be ~ 20% longer than the diameter of the recipient nerve. Great care must be taken not to damage the underlying axons ( Fig. 15.7 ).
The distal, recipient stump of the damaged nerve must be “cleanly” transected and normal (i.e., no bruising or fraying).
The stump must be gently released from the surrounding tissue to allow easy transposition to the donor nerve.
The recipient nerve must lie in healthy tissue.
No tension whatsoever should be present, even when moving proximal and distal joints.
No kinking (acute angle of the nerve) should be allowed; a smooth, gentle curve should be aimed for.
Great care must be taken not to damage underlying axons when making the epineurial window.
The epineurial window must lie in the same plane as, and on the side of, the approaching recipient nerve (again, to prevent any kinking).
Four to eight 8.0 Prolene epineural sutures are used to attach the recipient nerve to the donor nerve window.
Ensure a very gentle approximation. It is better to leave a small gap than to do a too-tight suture, which may kink (buckle) the ends of the recipient axons. “Approximate, do not strangulate!”