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Mitchell et al. Plast Aesthet Res 2023;10:35 https://dx.doi.org/10.20517/2347-9264.2023.14 Page 3 of 12

Elbow flexion
The favored technique for elbow flexion restoration, while using the SAN to SSN transfer for shoulder
motion, is a direct nerve transfer of ICN to the MCN. A 2018 meta-analysis has shown improved function
[8]
and decreased comorbidity of transferring two ICN over three or four . To accomplish this, a curved
incision along the sixth intercostal space from sternum to axilla is completed. Soft tissue is retracted
superiorly, and the 5th and 6th ribs are exposed. ICN 5-6 are dissected from the inferior border of their
corresponding rib and sectioned at the level of the costochondral junction. Next, a longitudinal incision is
made along the proximal medial arm, posterior to the biceps muscle belly. The overlying fascia at the
interval between the biceps and the coracobrachialis is incised, and the MCN, along with biceps motor
branch, is identified. The MCN is transected at least 1 cm proximal to its insertion into the biceps allowing
room for coaptation. The ICN is then reflected into the axilla to the MCN [Figure 1]. The shoulder is
abducted to 90 degrees and externally rotated during repair to ensure a tensionless neurorrhaphy. This
technique negates the need for an interposition nerve autograft along with donor morbidity and worse
associated outcomes [9,10] .

Functional results for this transfer have seen improvement over time, with 42%-90% of patients regaining
elbow flexion to a British Medical Research Council (MRC) grading system, strength grade 3 or greater.
One study showed nearly 40% of patients improved to grade 4 [11-13] . In comparison, a meta-analysis from
2001 suggested that the SAN to MCN transfer produced a significantly lower likelihood of obtaining
[12]
functional elbow flexion . Furthermore, compared to the phrenic nerve transfer, there were no statistical
[14]
differences in the final MRC grade or EMG results . This is important to note as the ICN transfer does not
require a nerve graft and eliminates the possibility of diaphragm paralysis/pulmonary complications with
the sacrifice of the phrenic nerve.

Shoulder stabilization/abduction
When addressing shoulder stabilization and abduction, extra-plexal nerve transfers from the SAN to the
SSN are preferred. For this procedure, a supraclavicular approach is used, and the proximal brachial plexus
is explored. The target SSN is identified as branching from the upper trunk and traversing through the
suprascapular notch. The SAN is isolated on the deep surface of the trapezius muscle. The SAN is dissected
as distally as possible prior to transecting it to maximize length for coaptation [15-17] . Similarly, the SSN is
transected as it branches from the upper trunk, preserving as much length as possible. A tension-free
coaptation is then performed between the two nerves [Figure 2].

Previous studies have demonstrated encouraging outcomes, with 70%-90% returning good/excellent
abduction results through the supraspinatus. Additionally, SAN to SSN fared significantly better than SAN
to axillary nerve transfers in regaining functional shoulder abduction in 92% of patients compared to
69% [12,18] .

Elbow extension
To restore elbow extension, ICN 3-4 to the triceps motor nerve is the procedure of choice in this
reconstruction methodology. Meticulous dissection along the inferior border of the corresponding ribs
from the costochondral junction to the axilla is required to isolate the longest ICN for transfer. The radial
nerve motor branch to the long head of the triceps is identified as the radial nerve proper crosses distal to
the teres major. Once isolated, this motor branch can undergo direct coaptation to ICN 3-4. Again, this is
done with the arm abducted to 90 degrees and externally rotated to ensure tensionless coaptation [9,19] .