Motor Nerve Transfers to Restore Extrinsic
Median Nerve Function: Case Report
Eugene C. Hsiao & Ida K. Fox & Thomas H. Tung &
Susan E. Mackinnon
Received: 2 June 2008 /Accepted: 7 August 2008 /Published online: 19 September 2008
# American Association for Hand Surgery 2008
Abstract Active pronation is important for many activities
of daily living. Loss of median nerve function including
pronation is a rare sequela of humerus fracture. Tendon
transfers to restore pronation are reserved for the obstetrical
brachial plexus palsy patient. Transfer of expendable motor
nerves is a treatment modality that can be used to restore
active pronation. Nerve transfers are advantageous in that
they do not require prolonged immobilization postopera-
tively, avoid operating within the zone of injury, reinnervate
muscles in their native location prior to degeneration of the
motor end plates, and result in minimal donor deficit. We
report a case of lost median nerve function after a humerus
fracture. Pronation was restored with transfer of the
extensor carpi radialis brevis branch of the radial nerve to
the pronator teres branch of the median nerve. Anterior
interosseous nerve function was restored with transfer of
the supinator branch to the anterior interosseous nerve.
Clinically evident motor function was seen at 4 months
postoperatively and continued to improve for the following
18 months. The patient has 4+/5 pronator teres, 4+/5 flexor
pollicis longus, and 4−/5 index finger flexor digitorum
profundus function. The transfer of the extensor carpi
radialis brevis branch of the radial nerve to the pronator
teres and supinator branch of the radial nerve to the anterior
interosseous nerve is a novel, previously unreported method
to restore extrinsic median nerve function.
Peripheral nerve injuries and their resultant motor deficits
are a challenging problem for the reconstructive surgeon. If
the injured nerve can be repaired primarily, with or without
a nerve graft, functional improvement relies on reinnerva-
tion prior to degeneration of the motor end plates. If the
nerve repair is not done in a timely fashion or the distance
to the motor end plate is prohibitive, fiber regeneration will
result in acceptable sensory function but poor motor
function. The lost motor function has been traditionally
treated with a variety of tendon transfers.
In median nerve palsy, tendon transfers can restore
opposition and thumb and finger flexion. Thumb opposition
is restored by transfer of a variety of tendons such as the
flexor digitorum superficialis (FDS) [4, 19, 21], extensor
indicis proprius (EIP), abductor digiti minimi (ADM) ,
or palmaris longus  transfer. Flexor pollicis longus
(FPL) function can be restored by brachioradialis tendon
transfer . Lost median innervated flexor digitorum
profundus (FDP) function can be restored by side to side
tenodesis to the functioning ulnar innervated FDP tendons
. These tendon transfers restore the majority of median
innervated function; however, the median nerve also
innervates the two pronators of the forearm—pronator teres
While good functional results exist for the tendon
transfers mentioned above, there are few tendon transfers
described to reestablish adequate pronation. These are used
in the treatment of obstetrical brachial plexus injuries.
Active pronation can be restored by rerouting the brachior-
HAND (2009) 4:92–97
E. C. Hsiao:I. K. Fox (*):T. H. Tung:S. E. Mackinnon
Department of Surgery,
Division of Plastic and Reconstructive Surgery,
School of Medicine, Washington University,
660 S Euclid, Campus Box 8238,
Saint Louis, MO 63110, USA
adialis , biceps , supinator , or transferring the
course of the brachialis . To our knowledge, these tendon
transfers have not been used to restore pronation in cases of
isolated peripheral nerve injuries.
The ability to actively pronate the upper extremity is
important for independent activities of daily living, includ-
ing feeding oneself and personal hygiene . The inability
to pronate also creates difficulty in performing other simple
tasks such as opening jars or turning doorknobs . The
pronator teres is the muscle that primarily powers pronation
. While restoring pronation with the use of tendon
transfers is a viable option, reinnervation of one of the
native pronator muscles is preferable.
The use of nerve transfers as a treatment modality has
become increasingly popular, as it directly restores function
to the denervated muscle [11–13, 15–17, 23–26]. Unlike
tendon transfers, nerve transfers do not require prolonged
postoperative immobilization, and restore function to the
muscle in its original position and optimal sarcomere
length. Nerve transfer for restoration of pronation after
high median nerve injury may be the optimal means to
restore this vital function.
We report a case of a median nerve palsy secondary to a
proximal humerus fracture. Motor deficits were treated with
transfers of the supinator branch of the radial nerve to the
anterior interosseous nerve (AIN) and extensor carpi
radialis brevis (ECRB) branch of the radial nerve to the
pronator teres branch of the median nerve. This case report
focuses on the novel approach of using nerve transfers as a
modality to restore motor function after a proximal median
Materials and Methods
History and Physical Examination
A 65-year-old right hand dominant female noted signifi-
cant burning pain and loss of function in the median nerve
distribution of her left upper extremity after sustaining a
displaced left proximal humerus neck fracture from a fall
in July 2006. Her fracture was treated with open reduction
and internal fixation without complication. The nerve was
not explored at the time of fracture treatment. Postoper-
atively, the patient continued to have median nerve
dysfunction, which did not improve over a 5-month
On physical exam, the patient held her left hand in a
supinated posture. On standard motor testing, she had 0/5
function of her pronator teres, median innervated FDP, and
FPL resulting in no pinch or grip strength. In contrast,
pinch and grip strength of the contralateral extremity were
10 and 40 lbs, respectively. Sensory testing revealed no
functional two-point discrimination in the median nerve
distribution and 5 mm for the ulnar nerve distribution.
Electrodiagnostic studies performed 5 months after her
initial injury confirmed the presence of a severe left median
neuropathy. Needle electromyography of the pronator teres,
flexor carpi radialis (FCR), and abductor pollicis brevis
(APB) showed fibrillations and positive sharp waves. No
motor unit potentials were seen in any of these muscles
on volition. Nerve conduction studies showed absent sen-
sory nerve action potentials in the median nerve. Com-
pound muscle action potential amplitude of the left
median nerve was 0.13 mV, motor conduction velocity
was 41.0 m/s.
Clinical Decision Making
Traditional treatment of nonrecovering closed nerve injury
would involve exploration at the level of injury with
subsequent therapy dictated by intraoperative findings.
However, in proximal nerve injuries, recovery of distant
motor function is unreliable because of the time required
for the regenerating nerve to reach the motor end plates. In
addition, the proximal exploration in the zone of injury and
the potential requirement for sural nerve grafting is not
Therefore, we proposed using expendable motor
branches from the radial nerve (the supinator and ECRB
branches) to reinnervate the pronator teres muscle and the
AIN. This would avoid operating in the zone of injury and
bring the repair site closer to the targeted motor end plate.
Supination would be maintained by the biceps brachii, and
wrist extension would be provided by the extensor carpi
radialis longus (ECRL) and extensor carpi ulnaris (ECU). If
recovered function was inadequate, conventional tendon
transfers could be performed at a later date to restore AIN
function. Restoration of sensation, which is not under any
time constraints, could be restored later with a sensory
An incision was made just distal to the antecubital crease.
The pronator teres insertion was step-lengthened and the
deep head of the pronator teres was cut to improve
visualization of the median nerve and its branches. The
median nerve and its branches were identified in order
from proximal to distal: pronator teres, FCR/palmaris
longus, AIN, FDS. A disposable nerve stimulator (Varis-
tim III, Medtronic) with a current of 2 mA was used to
stimulate the pronator teres branch and AIN within
30 min of tourniquet time. No muscle contraction was
noted which confirmed the preoperative physical exam
and electrodiagnostic findings. The pronator teres branch
HAND (2009) 4:92–97 9393
and AIN were neurolysed from the main trunk of the
The superficial radial nerve was identified in the same
incision and followed proximally to the main trunk of the
radial nerve. The nerve to the supinator is noted to come off
posteriorly from the main trunk of the radial nerve. The
ECRB nerve can branch off variably from either the main
trunk of the radial nerve, the PIN, or the superficial radial
nerve . The ECRL nerve branches off of the radial nerve
proximal to the antecubital fossa and is not seen during this
more distal dissection. Stimulation of the radial nerve
branches showed normal motor function. The branches
were dissected distally toward their target muscles. The
donor nerves (supinator and ECRB branches) were divided
distally, and the recipient nerves (pronator teres branch and
AIN) were divided proximally. This allowed tension-free
repair of the supinator branch to the AIN and the ECRB
branch to the pronator teres branch. Coaptations were
performed under the microscope with 9-0 nylon micro-
suture.(Figs. 1, 2, 3, and 4).
After surgery, the patient was placed in a light non-
immobilizing dressing. A sling was used for 1 week. Nerve
gliding and range of motion exercises were begun at
1 week. Motor retraining similar to that used in tendon
transfer with cocontracture of the donor and recipient
muscles was helpful. For example, the patient was
instructed to extend the wrist and pronate the forearm
simultaneously. Early retraining beginning, within 1 month
of surgery, expedited recovery. As function returned, at
about 4 months postsurgery, strengthening was begun.
Postoperatively, the patient showed evidence of pronator
function at 4 months and reinnervation of her FPL and FDP
at 8 months. At 1 year postoperatively, her grip strength was
11 lbs, pinch strength 5 lbs. At 18 months postoperatively,
her grip strength is 20 lbs, pinch strength 9 lbs. This
compares favorably to her contralateral values of 40 and 10,
respectively. Motor function has improved with pronator
teres at 4+/5, FPL at 4+/5, and index finger FDP at 4−/5. The
patient’s passive range of motion at the interphalangeal joint
of the thumb and distal interphalangeal joint of the index
finger were restricted, but the strength was good. The patient
Figure 2 Coaptation of supinator branch to anterior interosseous
nerve, extensor carpi radialis brevis branch to pronator.
Figure 1 Anatomy of median
and radial nerves. PIN posterior
interosseous nerve, ECRB ex-
tensor carpi radialis brevis
nerve, SBR superficial branch of
radial nerve, AIN anterior inter-
osseous nerve. AIN has been
neurolysed proximally to allow
coaptation to supinator branch.
Pronator branches (not seen) are
the first branches off of the
median nerve proximally.
94HAND (2009) 4:92–97
underwent a carpal tunnel release at 9 months, and the
patient declined further surgery to improve sensation in the
median nerve distribution. The patient is able to complete all
of her activities of daily living independently. She desired
more strength of her index finger flexion, and therefore,
underwent a tenodesis at 18 months postoperatively. The
patient has no donor site morbidity (Figs. 5 and 6).
Nerve palsies associated with humerus fractures typically
involve the radial nerve. Involvement of the median nerve
has also been reported, but is quite uncommon . When
this occurs, it is most commonly seen in children who
sustain supracondylar humeral fractures.
Nerve injuries that are treated with either primary repair
or nerve graft regenerate at 1 mm/day or 1 inch/month .
Although there is no time limit to sensory reinnervation,
target muscles must be reinnervated within 12–18 months
to have meaningful recovery. After this time, an insufficient
number of motor end plates remain for adequate function to
be restored. Nerve transfers have been described to restore
Figure 5 The 18-month postoperative results: a 4+/5 pronation; b 4+/
5 FPL function; c 4−/5 index finger FDP function.
Figure 4 Fascicular anatomy of median and radial nerve with
subsequent transfer of ECRB to PT and supinator to AIN.
Figure 3 Anatomy of median and radial nerve.
HAND (2009) 4:92–97 9595
function in peripheral nerve injuries. This treatment
modality is advantageous over direct repair or grafting of
proximal injuries because it shortens the distance for nerve
regeneration to the target muscle. This in essence converts a
proximal or high level injury to a low level injury .
Decreasing the distance for reinnervation with a distal nerve
transfer will shorten the time frame for nerve regeneration
and allow recovery of motor function.
In the patient described above, the lack of motor unit
potentials on electrodiagnostic studies 5 months after injury
suggest that meaningful recovery of motor function without
surgical intervention was unlikely. The proximal location of
her nerve injury also suggested that even with resection of
the damaged segment and interpositional nerve grafting,
nerve regeneration would not occur within the 18-month
time limit for adequate return of motor function. However,
by using nerve transfer to reinnervate closer to the target
muscle, we successfully restored function to her native
pronator teres and AIN innervated muscles.
The anatomy allowing the transfer procedure has been
well described. Specifically, the nerve branches to the
pronator teres are the most proximal branches of the median
nerve in the forearm. The pronator teres nerve most
commonly branches 0.4–2.3 cm below the median epicon-
dyle and typically has two main branches to its muscle
belly . The anatomy of the radial nerve branches distal
to the brachioradialis occurs in a predictable pattern. The
supinator and the ECRB are innervated distal to the ECRL.
We have noted that the supinator branch exits the main
trunk of the radial nerve posteriorly. The ECRB branch has
been noted to come off variably from either the posterior
interosseous nerve (PIN), the superficial branch of the
radial nerve, or the radial nerve prior to its bifurcation .
Although the donor and recipient nerve branches are
relatively close, one caveat for success with nerve trans-
fers in the upper extremity includes creating a tension-free
coaptation between the donor and recipient nerves. One
principle that we have stressed in the operating theater has
been to divide the nerves: “donor distal and recipient
proximal.” This is accomplished by neurolysing the
recipient nerves proximally off of their main trunk and
dissecting the donor nerve distally toward their target
muscle. This allows enough length to perform the
necessary transfers in a tension-free manner and permits
early range of motion.
Pronation is important in many activities of daily living
including eating, dressing, and writing. Loss of pronation
results in compensatory activities such as contralateral
trunk flexion combined with arm abduction. The supinated
posture severely limits arm and hand function.
Restoration of pronation through tendon transfers has
been described for the obstetrical brachial plexus patient.
Use in acquired deficits of the adult population to restore
pronation has not been reported. In this case, we report the
successful use of ECRB branch of the radial nerve to
reinnervate pronator teres in the context of a proximal
median nerve injury. Pronator function returned at 4 months
Similarly, we have previously described transfer of a
redundant motor branch to the FDS to the pronator teres
branch in two patients with rare cases of isolated loss of
pronation . Reinnervation was seen at 4 and 8 months,
We also were able to reinnervate the AIN through
transfer of the supinator branch of the radial nerve with
return of function at 8 months postprocedure. Transfer of
the supinator branch does not preclude future tendon
transfer to the AIN innervated muscles should motor
function be inadequate with nerve transfers. Though our
patient had excellent return of power in her reinnervated
muscles, residual stiffness in her thumb interphalangeal
joint and index finger distal interphalangeal joint limited
our results. However, donor nerves were obtained from
redundant radial nerve functions making donor site
In summary, we propose a novel method to restore
motor function after a complete high median nerve injury
that uses expendable donor nerves and should be
considered in the armamentarium of the peripheral nerve
and hand surgeon.
Figure 6 a–b No donor deficits
postoperatively. Patient has full
wrist extension and supination.
96HAND (2009) 4:92–97
1. Abrams RA, Ziets RJ, Lieber RL, et al. Anatomy of the radial
nerve motor branches in the forearm. J Hand Surg Am 1997;22:
2. Apergis E, Aktipis D, Giota A, et al. Median nerve palsy after
humeral shaft fracture: case report. J Trauma 1998;45:825–6.
3. Bertelli JA. Brachialis muscle transfer to the forearm muscles in
obstetric brachial plexus palsy. J Hand Surg Br 2006;31:261–5.
4. Bunnell S. Opposition of the thumb. J Bone Jt Surg Am 1938;20:
5. Camitz H. Uber die Behandlung der Oppositionslahmung. Acta
Chir Scand. 1929;65:77–81.
6. Chuang DC, Ma HS, Borud LJ, et al. Surgical strategy for
improving forearm and hand function in late obstetric brachial
plexus palsy. Plast Reconstr Surg 2002;109:1934–46.
7. Davis T. Median nerve palsy. In: Green DP, editor. Operative hand
surgery. Philadelphia, PA: Churchill Livingstone; 2005. p. 1131–59.
8. Haugstvedt JR, Berger RA, Berglund LJ. A mechanical study of the
moment-forces of the supinators and pronators of the forearm. Acta
Orthop Scand 2001;72:629–34. doi:10.1080/000164701317269076.
9. Huber E. Hilfsoperation bei median Uhlahmung. Dtsch Arch Klin
10. Kapandji A. Biomechanics of pronation and supination of the
forearm. Hand Clin 2001;17:111–22.
11. Mackinnon SE, Novak CB. Nerve transfers: new options for
reconstruction following nerve injury. Hand Clin 1999;15:643–66.
12. Mackinnon SE, Novak CB, Myckatyn TM, et al. Results of re-
innervation of the biceps and brachialis muscles with a double
fascicular transfer for elbow flexion. J Hand Surg Am
13. Mackinnon SE, Roque B, Tung TH. Median to radial nerve
transfer for treatment of radial nerve palsy. Case report. J
Neurosurg 2007;107:666–71. doi:10.3171/JNS-07/09/0666.
14. Manske PR, McCarroll HR Jr, Hale R. Biceps tendon rerouting
and percutaneous osteoclasis in the treatment of supination
deformity in obstetrical palsy. J Hand Surg Am 1980;5:153–9.
15. Novak CB, Mackinnon SE. Distal anterior interosseous nerve
transfer to the deep motor branch of the ulnar nerve for
reconstruction of high ulnar nerve injuries. J Reconstr Microsurg
16. Novak CB, Mackinnon SE. Surgical treatment of a long thoracic
nerve palsy. Ann Thorac Surg 2002;73:1643–5. doi:10.1016/
17. Novak CB, Mackinnon SE. Treatment of a proximal accessory
nerve injury with nerve transfer. Laryngoscope 2004;114:1482–
18. Ozkan T, Aydin A, Ozer K, et al. A surgical technique for
pediatric forearm pronation: brachioradialis rerouting with inter-
osseous membrane release. J Hand Surg Am 2004;29:22–7.
19. Royle ND. An operation for paralysis of the thumb intrinsic
muscles of the thumb. JAMA 1938;111:612–3.
20. Seddon H, Medaware P, Smith H. Rate of regeneration of
peripheral nerves in man. J Physiol 1943;102:191–215.
21. Thompson TC. A modified operation for opponens paralysis. J
Bone Jt Surg Am 1942;26:632–40.
22. Timm WN, O'Driscoll SW, Johnson ME, et al. Functional
comparison of pronation and supination strengths. J Hand Ther
23. Tung TH, Mackinnon SE. Flexor digitorum superficialis nerve
transfer to restore pronation: two case reports and anatomic
study. J Hand Surg Am 2001;26:1065–72. doi:10.1053/jhsu.2001.
24. Tung TH, Novak CB, Mackinnon SE. Nerve transfers to the
biceps and brachialis branches to improve elbow flexion strength
after brachial plexus injuries. J Neurosurg 2003;98:313–8.
25. Tung TH, Weber RV, Mackinnon SE. Nerve transfers for the
upper and lower extremities. Oper Tech Orthop 2004;14:213–22.
26. Weber RV, Mackinnon SE. Nerve transfer in the upper extremity. J
Am Soc Surg Hand2004;4:200–13. doi:10.1016/j.jassh.2004.06.011.
HAND (2009) 4:92–97 9797