Review Article Nerve Transfers for the Upper Extremity: New Horizons in Nerve Reconstruction Abstract Steve K. Lee, MD Nerve transfers are key components of the surgeon’s Scott W. Wolfe, MD armamentarium in brachial plexus and complex nerve reconstruction. Advantages of nerve transfers are that nerve regeneration distances are shortened, pure motor or sensory nerve fascicles can be selected as donors, and nerve grafts are generally not required. Similar to the principle of tendon transfers, expendable donor nerves are transferred to denervated nerves with the goal of functional recovery. Transfers may be subdivided into intraplexal, extraplexal, and distal types; each has a unique role in From the Hospital for Special the reconstructive process. A thorough diagnostic workup and Surgery and Weill Cornell Medical intraoperative assessment help guide the surgeon in their use. College, New York, NY. Nerve transfers have made a positive impact on the outcomes of Dr. Lee or an immediate family nerve surgery and are essential tools in complex nerve member has received royalties from, is a member of a speakers’ bureau reconstruction. or has made paid presentations on behalf of, and serves as a paid consultant to or is an employee of Arthrex; serves as an unpaid lthough not a new concept, neurotization should be reserved to consultant to Synthes; has received Anerve transfers have become an describe the direct implantation of a research or institutional support from increasingly important technique in divided donor nerve into muscle, Arthrex, DePuy Mitek, Integra LifeSciences, Medartis, Axogen, and the strategic algorithm for nerve re- which has shown promise in an ani- 1,2 Checkpoint; and serves as a board construction. Pioneers such as mal model. member, owner, officer, or Flouren introduced the rooster committee member of the American plexus model in 1820, Balance de- Society for Surgery of the Hand. Indications and scribed the spinal accessory nerve Dr. Wolfe or an immediate family Contraindications member has received royalties from (SAN) transfer to the facial nerve in Extremity Medical; is a member of a 1903, Vulpius described use of the speakers’ bureau or has made paid A variety of indications exists for presentations on behalf of Small medial pectoral nerve in 1920, and nerve transfer, primarily when the Bone Innovations and TriMed; Seddon, the transfer of intercostal proximal nerve end is nonfunctional serves as a paid consultant to or is nerves (ICNs) in 1963.1 an employee of Extremity Medical or nerve reconstruction would re- and Small Bone Orthopedics; and The definition of nerve transfer is quire an excessively long nerve graft. serves as a board member, owner, the surgical coaptation of a healthy Nerve transfer may expedite reinner- officer, or committee member of the nerve donor to a denervated nerve. vation when traditional nerve graft- New York Society for Surgery of the Hand. The principle is similar to that of ing would exceed the expected via- tendon transfers in that a necessary bility of motor end plates and muscle J Am Acad Orthop Surg 2012;20: 3 506-517 distal function is recovered by sacri- (approximately 12 to 18 months). ficing another function that is less es- Nerve transfer may also be indicated http://dx.doi.org/10.5435/ JAAOS-20-08-506 sential to the patient. Synonyms for in patients in whom the zone of in- nerve transfer are nerve-to-nerve jury is very broad, with dense scar- Copyright 2012 by the American neurotization, heterotopic nerve su- Academy of Orthopaedic Surgeons. ring. Nerve transfer outside the zone ture, and nerve crossing. The term of injury is more surgically efficient 506 Journal of the American Academy of Orthopaedic Surgeons Steve K. Lee, MD, and Scott W. Wolfe, MD and outcomes, more predictable.4 nerve to the axillary nerve, a fascicle promised recipient nerve.7 End-to- In the upper extremity, nerve trans- of the ulnar nerve to the biceps mo- end transfer is preferable for all fer is most commonly used for recon- tor branch, a fascicle of the median transfers; reverse end-to-side trans- struction of brachial plexus injury. nerve to the brachialis motor branch, fers have not been demonstrated to Other indications include complex and triceps branches of the radial improve motor outcomes in humans injuries to peripheral nerves, espe- nerve to the axillary nerve and its but do show experimental promise.7,8 cially when associated with fractures branches. Extraplexal refers to do- End-to-side transfers have demon- and dislocations, lacerations, injuries nor nerves that originate outside the strated efficacy in sensory nerves.3,6 from projectiles, neoplasia, or, oc- plexus. Examples include the SAN to The most common upper extremity casionally, neuralgic amyotrophy the suprascapular nerve (SSN) and deficits that benefit from nerve trans- (Parsonage-Turner syndrome). the ICN or phrenic nerve to the mus- fer are elbow flexion and shoulder sta- Contraindications for nerve trans- culocutaneous nerve (MCN). bilization, abduction, and external ro- fer include the presence of a superior Distal transfer: Nerve transfer that tation. Other indications include reconstructive option, excessive time is at or distal to the elbow. scapular stabilization for winging, el- between injury and reinnervation (ie, Single versus dual transfer: Single bow extension, wrist extension, finger >18 months), or donor nerve motor transfer refers to the use of one nerve and thumb extension, finger flexion, strength of less than Medical Re- transfer to achieve one action. An and intrinsic hand function. Tables 1 to search Council grade M4. example of a single transfer is an ul- 3 describe intraplexal, extraplexal, and nar nerve fascicle to the biceps motor distal motor transfers. Sensory deficits branch to achieve elbow flexion. of the thumb, index, ring and small fin- Advantages of Nerve Dual transfer refers to the use of two ger and ulnar border of the hand are Transfer nerve transfers to achieve one action. treated by nerve transfers listed in Ta- An example is an ulnar nerve fascicle ble 4. Nerve transfer has the distinct ad- to the biceps motor branch and a Intraplexal donors include the fol- vantage over primary nerve repair median nerve fascicle to the brachia- lowing: ulnar nerve fascicle, median and long nerve grafting of shortening lis motor branch to achieve elbow nerve fascicle, medial pectoral nerve, the length that the nerve must regen- flexion. thoracodorsal nerve, triceps branches erate by bringing the donor nerve Direct nerve transfer: A direct nerve of the radial nerve, brachialis branch of closer to the target organ.3,5 With transfer connects the donor nerve to the MCN, and pectoral fascicle from nerve transfer, pure motor fascicles the recipient nerve without an inter- the middle trunk of C7. with maximal axonal counts are di- posed graft. If a tensionless nerve co- Extraplexal donors include the fol- rected to a recipient nerve. Opti- aptation is not possible, an interposi- lowing: SAN, ICNs, phrenic nerve, mally, nerves are directly transferred tion nerve graft must be used. and contralateral C7 nerve root. to the recipient nerve without an in- Motor versus sensory transfer: Distal transfer donors include the terposed nerve graft. As opposed to Transfers with the goal of recovering following: distal anterior interosse- tendon transfer, when nerve transfer motor or sensory function. Transfers ous nerve (AIN), radial nerve branch is successful, recovered function is performed to restore sensory func- to the extensor carpi radialis brevis, similar to the original muscle func- tion have the added benefit of de- supinator branches of the posterior tion because synchronous physio- creasing neuropathic pain.6 interosseous nerve (PIN), and radial logic motion may be achieved. With End-to-end, end-to-side, reverse end- nerve branch to the brachioradialis. quicker nerve recovery, more rapid to-side: End-to-end nerve transfer refers motor reeducation is also possible. to direct coaptation of the end of the donor nerve to the proximal end of the Common Transfers and Outcomes Nomenclature recipient nerve (Figure 1). End-to-side nerve transfer describes coaptation of Intraplexal versus extraplexal: Intra- the proximal end of the recipient nerve Intraplexal Transfers plexal refers to nerve transfers in to an epineural window in the side of Ulnar Nerve Fascicle to Biceps which the donor nerve originates in an intact and functioning donor nerve. Motor Branch the brachial plexus, including the ter- Reverse end-to-side is when the end of Transfer of the ulnar nerve fascicle to minal peripheral nerve branches a freshly divided donor nerve is the biceps motor branch, described above the elbow. Examples include coapted to an epineural window in the by Oberlin et al9 in 1994, critically the medial pectoral or thoracodorsal side of an intact but functionally com- altered the approach to modern August 2012, Vol 20, No 8 507 Nerve Transfers for the Upper Extremity: New Horizons in Nerve Reconstruction Figure 1 Illustrations of the types of nerve transfer. A, End-to-end. B, End-to-side. C, Reverse end-to-side. nerve transfers. In this transfer, one individual fascicle (Checkpoint Sur- or central part of the nerve;10 any or two fascicles of the ulnar nerve gical Stimulator; Checkpoint Surgi- fascicles that give no response are are transferred directly to the motor cal, Cleveland, OH) and observing presumed to be sensory, and those branch of the biceps. In our practice, the distal muscular contraction. A that cause flexor