Anterior Interosseuos Nerve Transfer to the Motor Branch of the Ulnar Nerve - Haase

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Anterior Interosseous Nerve Transferto the Motor Branch of the UlnarNerve for High Ulnar Nerve Injuries

Steven C. Haase, MD

Kevin C. Chung, MD

Primary repair of a high ulnar nerve injury results in a uniformly

poor outcome as a result of the great distance between the site of

injury and the innervated muscles. In this study the authors

present two cases of high ulnar nerve injuries in adults. Recon-

struction was performed using the distal branch of the anterior

interosseous nerve, which was transferred to the distal motor

branch of the ulnar nerve. This resulted in timely return of

function to the ulnar-innervated intrinsic muscles of the hand,

which was documented further by electromyography. For high

ulnar nerve injuries, this type of nerve transfer is a much better

approach than the traditional primary neurorrhaphy.

Haase SC, Chung KC. Anterior interosseous nerve transfer to the motor

branch of the ulnar nerve for high ulnar nerve injuries. Ann Plast Surg2002;49:285290

From the Section of Plastic Surgery, Department of Surgery, The University

of Michigan Medical Center, Ann Arbor, MI.

Received Nov 1, 2001, and in revised form Jan 25, 2002. Accepted for

publication Jan 25, 2002.

Address correspondence and reprint requests to Dr Chung, Section of

Plastic Surgery, The University of Michigan Health System, 1500 E.

Medical Center Drive, 2130 Taubman Center, Ann Arbor, MI 48109-0340.

In adults, repair of high ulnar nerve injuries

those near or above the elbowhas historically

yielded unsatisfactory results, with minimal re-

covery of intrinsic muscle function and resultant

claw hand deformity.1 This is true despite the

most meticulous techniques, whether the repair

is primary or secondary, and regardless of

whether a nerve graft is used.2,3 Although sensa-

tion is restored most of the time, recovery of

motor function in the intrinsic muscles of the

hand is almost uniformly poor, especially in the

adult patient. This is principally the result of the

considerable distance between the site of injury

and the muscle motor end plates to be reinner-

vated. During the several months required for the

regenerating axons to traverse this gap, the dener-

vated muscles undergo irreversible atrophy and

fibrosis.

We present 2 patients who illustrate an alterna-

tive method for reconstructing high ulnar nerve

lesions. Transfer of the terminal branch of the

anterior interosseous nerve to the motor branch of

the ulnar nerve at the wrist should reduce greatly

the delay in reinnervation of the intrinsic muscles

and lead to an improved outcome. Our objectives

were to demonstrate the usefulness of this innova-

tive technique and to present the outcomes we

observed, including electromyographic evaluation

of the reconstruction.

Patient Reports

Patient 1

Patient 1 is a 41-year-old right-hand-dominant

carpenter who was involved in a motor vehicle

accident in which he sustained a complex right

upper arm laceration. The ulnar nerve was di-

vided 8 cm above the elbow, as was the medial

head of the triceps muscle (Fig 1). The wound

was closed initially at the referring hospital, and

the patient was sent to our institution for defini-

tive repair of the nerve injury.Within a week of injury, the patient was taken

to surgery, at which time the ulnar nerve was

transposed anteriorly and repaired. The anterior

interosseous nerve was divided at its most distal

point, where it entered the pronator quadratus

muscle (Fig 2). Guyons canal was opened and

the motor branch of the ulnar nerve was identi-

fied and traced proximally as far as possible,

where it was divided. This motor branch was

tunneled under the flexor tendons and was co-

apted to the transected anterior interosseous

nerve (Fig 3).

Six months after surgery there was evidence of

reinnervation of the intrinsic muscles of the hand

(Fig 4). Most notable was the return of function of

the interosseous (Fig 5), adductor pollicis, and

abductor digiti quinti muscles. Nerve conduction

studies were performed 11 months postopera-

tively. They revealed single motor unit recruit-

ment in the intrinsic muscles of the hand

Copyright 2002 by Lippincott Williams & Wilkins, Inc. 285DOI: 10.1097/01.SAP.0000015429.34256.34


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innervated normally by the ulnar nerve, consis-tent with proximal-to-distal regrowth.

Patient 2

Patient 2 is a 52-year-old man who was involved

in a motor vehicle accident, during which he

sustained partial degloving injury of the right

arm. This wound was covered initially with a

skin graft at another institution (Fig 6), and the

patient was referred to our center for definitive

reconstruction.

Approximately 6 weeks after the initial injury,the patient was taken to surgery for repair of a

15-cm ulnar nerve gap with two strands of sural

nerve graft (Fig 7). Distally, the anterior interosse-

ous nerve was coapted to the motor branch of the

ulnar nerve at the wrist, using a 7-cm sural nerve

graft (Fig 8). The nerve graft was used because of

a substantial amount of tension at the nerve

coaptation site with primary repair. Because flex-

ion of the small finger was already noticeably

weak, transfer of the flexor digitorum profundus

tendon of the small finger to the flexor digitorum

profundus tendon of the middle finger was per-

formed. The elbow wound was covered with a

gracilis muscle free flap.

One year postoperatively, the patients function

of his intrinsic muscles had returned almost

completely. He was able to abduct and adduct the

fingers of his right hand (Fig 9). He has regained

protective sensation along the ulnar side of his

hand. His elbow range of motion is normal (Fig

10).

Discussion

Ulnar nerve injuries at or above the level of the

elbow generally have a poor functional outcome

with traditional repair. Children with similar

injuries have better outcomes, most likely be-

cause of the increased plasticity of their nervous

systems.4

Regardless of age, muscle atrophy begins at the

moment of denervation, and if the elapsed time toreinnervation is long, the atrophic changes in the

muscle become irreversible. This explains why

functional recovery gets worse as the delay be-

tween the time of injury and the time of recon-

struction increases. Likewise, the more proximal

the nerve lesion, the less likely that adequate

recovery can occur once nerve regeneration

traverses the increased distance to the end organ

targets. Several investigators have sought to slow

down or to stop this muscle atrophy by external

or internal muscle stimulation during the dener-

vated period.5 These kinds of muscle stimulators

are largely experimental at this time.

To obtain a more satisfactory outcome, tendon

transfers have been considered an integral part of

reconstructing high ulnar nerve lesions.6 Without

tendon reconstruction, most patients are left with

clawed, weak hands. We have undertaken an

alternative method of reconstruction in isolated

high ulnar nerve injuries. The terminal branch of

the anterior interosseous nerve is a predominant

Fig 2. The arrow points to the anterior interosseousnerve at its entrance into the pronator quadratusmuscle. Note the accompanying anterior interosseousvessels.

Fig 1. The end of the proximally divided ulnar nervewas held by a pickup.

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motor nerve that innervates the pronator quadra-

tus muscle and sends a few sensory branches to

the wrist joint. This nerve can be transferred to

the distal motor branch of the ulnar nerve,

thereby greatly reducing the necessary distance

for axonal regeneration to the intrinsic muscles.

This type of nerve transfer was brought to our

attention by Mackinnon and Novak.7 A report

also exists in the Chinese literature that used

cadaveric analyses to demonstrate the feasibility

of this approach.8 Several features of this transfer

are attractive. The donor defect is essentially

negligible. The intact pronator teres muscle is

Fig 3. (A) The arrow points to therepair between the anteriorinterosseous nerve and the motorbranch of the ulnar nerve. (B)Diagram illustrating the anteriorinterosseous nerve transfer to the

motor branch of the ulnar nerve. N nerve; M muscle.

Fig 4. The right reconstructed hand hasrecovered intrinsic muscle function.

Fig 5. The patient is able to abduct and adduct the fingers.

Haase and Chung: Anterior Interosseous Nerve Transfer

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sufficient to pronate the forearm. Because the

transferred nerve is a pure motor nerve, there

should be no competition by sensory fibers for

motor pathways during reinnervation.

Reconstruction of this injury should provide

for sensation in the ulnar nerve distribution as

well. Fortunately, return of sensation is some-

what less problematic, because the sensory recep-

tors do not depreciate to the extent that muscle

atrophy occurs in motor units. Therefore, repair

of the ulnar nerve by primary repair or nerve graft

at the site of injury is still required to direct the

sensory axons to their destination in the hand.

Some groups have sought to shorten the recovery

time for these nerve pathways as well, proposing

a transfer of the median nerve sensory branch to

the ulnar sensory nerve at the wrist.9 This ap-

proach may leave the patient with an insensate

palm. We think that return of sensation down the

native pathways of the ulnar nerve, despite the

delay, should suffice to provide at least protective

sensation in most cases.

Fig 6. Skin graft over the elbow wound.

Fig 7. Proximal ulnar nerve repair using two strands ofsural nerve graft.

Fig 8. (A) The arrow points to the motor branch of the ulnar nerve. (B) The anterior interosseous to motor branch ofthe ulnar nerve was repaired using sural nerve graft (arrow).

Fig 9. The patient is able to abduct and adduct the fingers.


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Helpful adjuncts to this procedure are also

illustrated in these patient reports. Transfer of the

flexor profundus tendon of the small finger

and/or ring finger to that of the middle finger

recovers function that is lost with denervation ofthe ulnar portion of that muscle belly. Reinner-

vation of the more proximal ulnar-innervated

muscles (i.e., flexor carpi ulnaris) should occur in

a more traditional fashion after primary or sec-

ondary nerve repair at the elbow because the

connections to these more proximal muscles may

still be intact.

Reports of similar nerve transfer techniques

now exist in the literature. Transfer of a single

motor fascicle from the ulnar nerve to the biceps

muscle has restored elbow flexion in patients

with upper brachial plexus injuries.10 In an ani-

mal model, transfer of part of the ulnar nerve to a

transected median nerve has restored consider-

able function without substantial donor deficit.11

Certainly, the possibilities for future application

of this concept are not yet fully explored.

A valid criticism of this report is the inability to

rule out any MartinGruber connections in these

patients. However, anatomic studies have failed

to find these connections in the distal forearm; all

connections occurred more proximally.12 Al-

though no nerve conduction studies were ob-

tained preoperatively, our patients had no

clinical evidence of intrinsic muscle functionafter the initial ulnar nerve transection. Even if

subclinical connections had been present, they

would be severed with the distal transection of

the ulnar nerve at Guyons canal. Any reinnerva-

tion observed must be the result of regeneration

through the nerve connection that we created.

We succeeded in restoring intrinsic muscle

function in 2 patients who would have had neg-

ligible recovery by traditional means. For high

ulnar nerve injuries, the anterior interosseous

nerve transfer to the deep motor branch of the

ulnar nerve should be the preferred method for

intrinsic muscle reinnervation.

References

1 Gaul JS. Intrinsic motor recoverya long-term study of

ulnar nerve repair. J Hand Surg [Am] 1982;7A:502508

2 Barrios C, Amillo S, de Pablos J, et al. Secondary repair of

ulnar nerve injury. Acta Orthop Scand 1989;61:46 49

Fig 10. (A, B) Return of normal elbow flexion with a healed gracilisfree flap muscle.

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3 Vastamki M, Kallio PK, Solonen KA. The results ofsecondary microsurgical repair of ulnar nerve injury.J Hand Surg [Br] 1993;18B:323326

4 Allan CH. Functional results of primary nerve repair.Hand Clin 2000;16:6772

5 Williams HB. A clinical pilot study to assess functionalreturn following continuous muscle stimulation afternerve injury and repair in the upper extremity using acompletely implantable electrical system. Microsurgery1996;17:597 605

6 Trevett MC, Tuson C, de Jager LT, et al. The functionalresults of ulnar nerve repair: defining the indications fortendon transfer. J Hand Surg [Br] 1995;20B:444 446

7 Mackinnon SE, Novak CB. Nerve transfers: new optionsfor reconstruction following nerve injury. Hand Clin 1999;15:643666

8 Wang Y, Zhu S, Zhang B. [Anatomical study and clinicalapplication of transfer of pronator quadratus branch ofanterior interosseous nerve in the repair of thenar branch

of median nerve and deep branch of ulnar nerve.] [In

Chinese.] Chung-Kuo Hsiu Fu Chung Chien Wai Ko Tsa

Chih 1997;11:335337

9 Battiston B, Lanzetta M. Reconstruction of high ulnar

nerve lesions by distal double median to ulnar nerve

transfer. J Hand Surg [Am] 1999;24A:11851191

10 Sungpet A, Suphachatwong C, Kawinwonggowit V, et al.

Transfer of a single fascicle from the ulnar nerve to the

biceps muscle after avulsions of upper roots of the bra-chial plexus. J Hand Surg [Br] 2000;25B:325328

11 Lutz BS, Chuang DCC, Chuang SS, et al. Nerve transfers to

the median nerve using parts of the ulnar and radial

nerves in the rabbit effects on motor recovery of the

median nerve and donor nerve morbidity. J Hand Surg [Br]

2000;25B:329335

12 Shu HS, Chantelot C, Oberlin C, et al. MartinGruber

communicating branch: anatomical and histological

study. Surg Radiol Anat 1999;21:115118


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Anterior Interosseuos Nerve Transfer to the Motor Branch of the Ulnar Nerve - Haase