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Titolo et al. Plast Aesthet Res 2023;10:21 https://dx.doi.org/10.20517/2347-9264.2022.113 Page 7 of 13

to short distance for regeneration, the synergistic activation of fifth finger flexion to enhance relearning of
[46]
thumb opposition and because represents an expendable donor in the hand . Transfers can be employed
to restore sensibility and to decrease neuropathic pain in MN defects, in particular, to the ulnar side of the
thumb and the radial side of the index finger to ensure pinch and grip functions; multiple donors have been
considered depending on their availability: the best donors are the digital nerves to the fourth web space
(UN), where, in order to provide limited non-critical protective sensation to the donor territories, an end-
to-side coaptation can be performed; another option is the dorsal sensory branch from the RN to the
thumb [45,48] .

In the case of UN motor branches lesions at the hand level, Bertelli proposed transferring the motor branch
[51]
of the opponens pollicis to the terminal division of the deep branch of the UN for pinch reconstruction
[Figure 2]; Gesslbauer, instead, proposed a nerve graft, bridging the thenar branch of the MN to the UN to
enhance nerve recovery with both end-to-side coaptations : in this case, the scope of the distal nerve graft
[52]
is to maintain some ulnar intrinsic muscle function while awaiting recovery in the main branch of the UN.
The main target and donor nerves are summarized in [Table 1].

Tendon transfers
When nerve structure repair is not possible or time for nerve recovery has long passed without a satisfactory
result, the movement has traditionally been restored by tendon transfers; the aim of this surgery is to shift a
safe, or recovered, muscle tendon to an injured site . To perform a tendon transfer, the following common
[53]
principles must be respected: supple joints; a healthy tissue environment; sufficient excursion and strength
(at least M4) of the donor unit; the primary function of the donor unit, which should focus on a sole motor
function, can be ensured by other units; the direction of the transfer should be as close to a straight line
between origin and insertion as possible; lastly, the patient’s capacity and motivation to follow an extensive
course of rehabilitation must be evaluated [53-55] . In MN injuries, the opposition can be restored using tendons
of the flexor digitorum superficialis (FDS) of the ring or middle finger or tendon of palmaris longus
(PL) [54,55] ; when the FDS of the ring finger is transferred, the tendon is harvested distally in the palm and
then withdrawn at the wrist. A strip of FCU attached to the pisiform can be employed to create a pulley
through which the FDS tendon passes to create a line of pull in the direction of the pisiform that reproduces
true opposition. Performing the Camitz opponensplasty, the PL, when present, is harvested in continuity
with a strip of superficial palmar aponeurosis and attached to the insertion of the abductor on the base of
the thumb’s proximal phalanx; however, since the line of pull is in the direction of the forearm, this transfer,
while simple and fast, acts more like an abductorplasty instead of a true opponensplasty [54-56] .

Another technique frequently used for MN palsy is the extensor indicis proprius to opponensplasty transfer,
which is a popular procedure in case of high MN palsy and when the ring and middle finger FDS tendons
are unavailable; it has also become preferable with respect to the superficialis tendon transfer in low MN
palsies because it does not weaken grip and causes little disability .
[57]
Two main motor dysfunctions are produced as a result of UN injury in the hand: ring and little fingers
clawing and thumb adduction impairment.

Bouvier’s test is essential to choose the best surgical option for claw correction: while the MP joint of the
examined digit is retained in flexion, the patient is asked to extend the IP joint of the same digit; when it is
possible to do so, the test is considered positive. In these cases, “static” procedures might be performed:
Zancolli described a technique in which the MCP joint is prevented from hyperextending by advancing
proximally a distally based flap of the volar plate of the MP joint and reattaching it to the metacarpal neck