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fibrosus is divided, and the radial vascular bundle, and to the extensor digiti minimi and extensor carpi ulnaris)
the median nerve are identified. Distally, step lengthening via interposition graft have been described, but results
of the superficial part of the PT allows better medial are uncertain and thus common tendon transfers might
retraction of the muscle so as to visualize the branches of be considered instead. [15]
the median nerve to the FDS and FCR. Lateral retraction
of the brachioradialis exposes the superficial radial nerve, Schematic description
the PIN, and the ECRB branches. Once both the donor A carpal tunnel incision is made to expose the median
branches to the FDS and FCR and the recipient branches nerve and its motor branch at the level of the wrist. The
are identified, they are isolated as needed in order to latter is gently isolated proximally as far as its fibers can
divide them following the rule of “donor distal/recipient be distinguished. The AIN and its branch to the pronator
proximal” described by Brown and Mackinnon, without quadratus are then isolated with intramuscular dissection
[15]
tension on the nerve coaptation. in order to obtain the maximal possible length. A nerve
graft is usually necessary for a tension‑free closure.
Sensory Although the number of axons matches well, the need
The lateral antebrachial cutaneous nerve (LACN) runs close for a nerve graft downgrades the level of outgrowth and,
to the sensory radial branch in the distal forearm and therefore, the actual potential for re‑innervation.
matches it very well in size. It is expendable, and its use
does not create any significant morbidity along its territory. Pronator function
The pronator teres function can be impaired in high median
[40]
MEDIAN NERVE DEFICITS nerve injuries or secondary to an isolated deficit. In the
first case the radial nerve, and specifically the motor branch
Indications to the ECRB is isolated and re‑oriented to the branch,
[41]
In high‑level injuries of the median nerve both extrinsic which innervates the PT. The surgical approach is similar
and intrinsic muscles of the forearm and hand, as well to that described for radial nerve palsy when the opposite
as the sensation on the volar‑radial part of the hand, are transfer is planned. In case of isolated PT deficiency, an
affected and need restoration. In low‑level injuries thumb, intra‑median nerve transfer is planned using one of the
[40]
opposition and sensation in the 1st, 2nd, 3rd, and radial branches to the FDS sutured to the PT motor branch.
half of the 4th fingers are addressed for reconstruction. Extrinsic muscle function
The most common donor is the radial nerve and its In high‑level median nerve injury several extrinsic muscles
branches to the supinator and ECRB. In case of isolated such as PT, FCR, FDS, flexor pollicis longus, the radial
injuries to the anterior interosseous nerve (AIN), component of the FDP, and PQ are denervated. Two
intra‑median nerve transfers have been described using main problems are faced: first, the lack of flexion in the
intact branches of the median nerve which are redirected. thumb, index and the long fingers, and second, the loss
[15]
Motor nerve transfers of pronation. The first option is to re‑direct the motor
Thumb opposition branch to the ECRB towards the AIN, in a similar fashion
described above for radial nerve palsy, but in a reverse
When available the AIN (branch to the pronator quadratus) direction [Figure 3]. If there is a significant discrepancy
is isolated and transferred to the motor branch of the in size, the branch to the supinator can also be included.
thenar muscles [Figure 2]. The donor and recipient match
well in size, but transfer requires a nerve graft which leads
to the inevitable loss of some of the regenerating axons. In
high‑level injuries, ulnar nerve to median (third lumbrical
motor branch) or radial nerve to median (motor branch
[39]

Figure 3: High median nerve deficit. Transfer of the motor branch
to extensor carpi radialis brevis to the anterior interosseous nerve.
Figure 2: Distal median nerve deficit. Transfer of the terminal branch ECRB: Extensor carpi radialis brevis, PIN: Posterior interosseous nerve,
of the anterior interosseous nerve to the motor branch to the thenar AIN: Anterior interosseous nerve, FCR: Flexor carpi radialis, FDS: Flexor
muscles, using an interpositional graft. AIN: Anterior interosseous nerve digitorum superficialis, PL: Palmaris longus
Plast Aesthet Res || Vol 2 || Issue 4 || Jul 15, 2015 197