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Page 2 of 20 Azoury et al. Plast Aesthet Res 2020;7:4 I http://dx.doi.org/10.20517/2347-9264.2019.44

INTRODUCTION
Harold Gillies introduced the reconstructive ladder for traumatic extremity wounds based on his
experience during World War I. Decades later, the senior author (Levin LS) revisited this concept when
he coined the collaborative orthoplastic approach between orthopedic and plastic surgeons in extremity
[1,2]
reconstruction . He elaborated on the necessity of a surgeon to be well versed with the various rungs
of the reconstructive ladder. Although variations to the original ladder have been described as the
[3-7]
reconstructive armamentarium expands with time, the basic tenants remain largely unchanged . Most
[3]
descriptions begin with healing by secondary intention on the lowest rung . The next lower-level rungs
of the ladder include simpler reconstructive options such as the use of split-thickness skin grafts and local
tissue rearrangements and the higher rungs represent complex techniques such as free tissue transfer.
In general, the simplest option that is able to cover the defect adequately and replace the missing tissue
components should be the reconstruction of choice. However, it is understood that a more complex option
such as free tissue transfer may be more appropriate even when simpler means achieve closure, such as
the cases of severe traumatic wounds with associated fracture repair, hardware, or in the case of oncologic
reconstruction when future radiation is anticipated.

Targeted muscle reinnervation (TMR) and osseointegration (OI) have added additional options for
mutilating lower extremity injuries that necessitate amputation [8-13] . More recently, the senior author
[14]
Levin described the “penthouse” floor of the reconstructive ladder being vascularized composite
allotransplantation (VCA). Despite the successes of prosthetic technology and targeted muscle
reinnervation, transplantation offers the ability to restore sensation, fine motor control, and tactile
aesthetics while improving overall quality of life [15,16] . Herein, the authors review TMR, OI, and VCA as
additional higher rungs of the reconstructive ladder [Figure 1].

TARGETED MUSCLE REINNERVATION
Background
When a limb is lost, there are residual muscles rendered incompetent without a joint to act across. Similarly,
there are nerves that not only are purposeless without distal targets to reinnervate, but can also become a
functional hindrance should they form a chronically painful neuroma. TMR was originally developed to
make use of these redundant muscles and nerves in amputees for improved upper extremity prosthetics.
In TMR, nerves transected during amputation are coapted to nearby motor nerves of redundant muscles,
providing a conduit to grow along and a muscle to reinnervate. The muscle acts as a biologic amplifier,
creating a myoelectric signal that can be picked up through surface electromyography (EMG). This signal
detection can be further amplified surgically by superficializing and separating the myoelectric unit from
other nearby signals. Signal mapping and feedback then allows for complex movement of a myoelectric
prosthesis.

Evidence for the functional capabilities of TMR in providing advanced prosthetic control came in the form
of myoelectrical signal decoding involving physical and practical movements with a prosthetic arm. As
research evolved, it was shown that pattern recognition technology could allow for intuitive movement-
learning, potentially enhancing both control and timing of movements through the prosthetic limb as an
alternative to conventional prosthetics that were plagued with slower learning due to a rather unintuitive
[17]
motion process . The research demonstrated that not only is TMR effective in allowing for complex
physical movements, but was also efficient in signal transmission and producing these movements relatively
[17]
quickly, a crucial consideration in functional validity .

Initial reservations in employing TMR included the possibility of creating more nerve pain during the
[17]
procedure . Coapting a nerve that is transected during amputation to a previously intact motor nerve