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Toyoda et al. Plast Aesthet Res 2022;9:17 https://dx.doi.org/10.20517/2347-9264.2021.118 Page 7 of 17

[50]
new frontier for machine learning in the clinical arena . Although not executed clinically, there have also
been discussions comparing and contrasting upper extremity transplantation and TMR. There are
advantages to both operations, with transplantation classically more beneficial for below mid-forearm
[51]
amputations and TMR more beneficial for above-elbow amputees . However, the authors conclude that
these operations are complementary, not competitive procedures . In fact, the physiology is the same: the
[51]
proximal arm relies on nerve regeneration to reinnervate the new, distal donor muscles to achieve motor
function and sensory recovery. In this sense, one can argue that upper extremity transplantation is perhaps
the ultimate TMR.

During these endeavors to treat upper extremity amputees, a retrospective review of fifteen patients who
underwent either shoulder disarticulation or transhumeral amputation and had neuroma pain who then
received TMR for myoelectric control demonstrated an unexpected finding of fourteen of these patients
having complete resolution of pain in the transferred nerves . These results were corroborated in a rabbit
[52]
[53]
forelimb amputation model by Kim et al. . After initial rabbit forelimb amputation, in a secondary
procedure, neuromas were excised at the median, radial, and ulnar nerves, and the proximal ends were
coapted to muscle nerves on a pedicled rectus abdominis flap . After ten weeks, there was successful
[53]
coaptation on EMG and better histological features of the neuroma with reduced myelinated fiber counts
[53]
and larger fascicle diameter . These findings significantly broadened the use of TMR for post-amputation
[54]
neuroma pain, particularly for lower extremity amputation . The functionality of lower extremity
amputees is very different from that of the upper extremity. Myoelectric or active lower limb prosthetics are
not as commonly used, and per the LEAP study, patients often regain functionality with standard prosthetic
use . However, as noted in numerous studies, prosthetics use is negatively correlated with post-amputation
[6]
pain. With the expansion of TMR for treatment of residual limb and PLP, its indications for use in the lower
extremity exploded.

Surgical technique of TMR
Symptomatic neuromas are diagnosed based on history and physical exam. Intraoperatively, the proximal,
cut, mixed motor/sensory, or sensory nerves with symptomatic neuromas are identified. Nerves with
neuromas are cut back to a fresh edge unaffected by scar tissue. Small motor nerves of nearby muscles are
identified. There are several papers with anatomical roadmaps for both upper and lower extremities to
identify the major branch points of motor nerves and motor entry points on muscles [41,55-58] . Handheld
neurostimulators can also be used intraoperatively to identify the locations of these nerves . These
[59]
neurostimulators, such as those from Checkpoint Surgical (Cleveland, OH), do not result in neuronal
fatigue despite repeated stimulation when identifying the nerves. Retrograde stimulation to trace the motor
nerve entry point is useful . Once these motor nerves are identified, they are dissected and cut proximally.
[60]
The distal motor nerve and the prepared sensory nerve are coapted usually with 6-0, 7-0, or 8-0
[60]
nonabsorbable monofilament suture through the epineurium . Others have described methods in which a
single 8-0 suture is placed in the center of the recipient nerve to loosely intussuscept the motor branch into
the center of the donor nerve, then reinforcing this with several interrupted 6-0 suture on the epineurium to
[59]
the fascia and epimysium around the target nerve [Figure 2] . The excision of the prior neuroma can be
coded as excision of major peripheral neuroma (64784), and TMR can be coded as pedicle nerve transfers
(64905).

The authors’ preferred technique for a BKA includes the use of a fishmouth incision with a posterior
myocutaneous flap as described by the Attinger group . In brief, the ideal tibial osteotomy is marked on
[61]
the anterior leg approximately 4 finger breadths or 10-15 cm from the tibial tubercle. The fibular osteotomy
should be 1-2 cm shorter than the tibial osteotomy. The anterior skin incision is made 1 cm distal to the
planned tibial osteotomy. This line is carried through the lateral axis of the calf, which is defined as