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Page 8 of 12 Bryan et al. Plast Aesthet Res 2022;9:53 https://dx.doi.org/10.20517/2347-9264.2022.39

FCR to PIN
Technique: This technique utilizes a branch of the median nerve, the nerve to Flexor Carpi Radialis (FCR),
for reinnervation of the PIN. A proximal, volar forearm incision is made below the antecubital fossa. The
FCR branch of the median nerve is identified with nerve stimulation, with stimulation causing wrist flexion.
The PIN can then be found by following the radial sensory nerve proximally. Following identification, the
[28]
PIN is divided proximally, and the FCR is divided distally to allow tension-free coaptation .
Outcomes: Previous reports demonstrated good wrist and finger extension results. As described earlier,
Mackinnon et al. reported a transfer of FDS to ECRB and FCR to PIN . At 18 months postoperatively, the
[28]
patient gained MRC grade 4 finger and wrist extension strength . Additionally, García-López et al.
[28]
reported 6 cases of nerve to the pronator teres (PT) to nerve to ECRL and nerve to FCR to PIN in patients
[35]
with radial nerve palsy or posterior cord injuries . After 20 months, all patients recovered MRC grade 4
ECRL strength with PT to ECRL transfer. With FCR to PIN transfer, 2/6 recovered MRC grade 3 and 4/6
recovered MRC grade 4 metacarpophalangeal extension and ECU strength. All patients recovered MRC
grade 4 thumb extension strength . As previously described, in Bertelli’s case series of 14 patients who
[35]
received AIN to ECRB and FCR to PIN, 8/14 recovered M4 and 4/14 recovered M3 finger extension, and
13/14 recovered M4 wrist extension. 11/14 recovered full thumb extension .
[34]

Summary: FCR to PIN has shown good results with 18/21 cases of FCR to PIN recovering MRC grade 4 and
3/21 recovering MRC grade 3 wrist extension strength. In addition to wrist extension, 13/21 recovered MRC
grade 4, and 6/21 recovered MRC grade 3 finger extension strength. Finally, 18/21 recovered full thumb
extension.

Supinator to PIN
Technique: This technique transfers the nerve to the supinator to the PIN [Figure 4]. On the dorsal side of
the arm, an incision is made at the level of the lateral epicondyle between the ECRL and brachioradialis.
Careful dissection is essential to preserve branches of the posterior antebrachial cutaneous nerve, which
provides sensation to the posterior portion of the forearm . Once the brachioradialis and ECRL are
[19]
identified, dissection in this interval allows exposure of the superficial branch of the radial nerve, PIN and
supinator branches. Alternatively, the supinator can also be exposed by dissecting in the interval between
[36]
the ECRB and EDC . Finally, a volar approach can also be used, dissecting radially deep to the
brachioradialis muscle to expose the branches of the radial nerve. These nerves can be identified by
stimulation, with contraction of the supinator confirming its branches and PIN stimulation not causing
contraction of the EDC, ECU, EPL and EIP in the setting of injury. The supinator branch is then divided
distally, and the PIN is divided proximally to allow for tension-free coaptation .
[19]
Outcomes: The supinator to PIN technique is widely documented in the literature and described as the most
reliable technique for achieving good outcomes for restoring finger extension . In 2015, Bertelli et al.
[19]
described a case series of 7 patients and thirteen limbs that received supinator to PIN transfer . After 19
[37]
months, 12/13 achieved at least MRC grade 3 thumb and finger extension, with 8 achieving MRC grade 4
thumb extension. The last limb regained MRC grade 2 function . In another series by Bertelli et al., 7
[37]
patients with tetraplegia received nerve to the supinator to PIN or gracilis muscle transfer to the extensor
compartment of the forearm . After 26 months, 3/3 upper limbs receiving nerve transfer recovered MRC
[38]
grade 3 thumb and finger extension, compared to none of the patients with gracilis transfer scoring above
MRC grade 2 . In 2018, Emamhadi et al. described a case report of a patient with tetraplegia after a C6
[38]
[36]
burst fracture who received brachialis to AIN and supinator to PIN nerve transfer . From the supinator to
PIN transfer, the patient achieved MRC grade 3 on thumb extension and MRC grade 4 on finger extension.