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Page 14 of 17 Qiu et al. Plast Aesthet Res 2022;9:19 https://dx.doi.org/10.20517/2347-9264.2021.126

axonotmesis can often be incorrectly attributed to neuropraxia or some other cause. Patients may end up
pursuing months of observation or other therapy while the window of opportunity to achieve reinnervation
narrows. In general, awareness of PNIs and reconstructive options is low, and we suspect many patients and
their providers are unaware of the options available to them.

Ultimately, our ability to achieve optimal outcomes is limited by anatomical and physiological parameters.
Tibial and femoral nerve injuries tend to fare well, but sciatic and common peroneal nerve injuries - which
comprise the majority of lower extremity PNIs - have worse results. In fact, segmental CPN injuries have
such poor regenerative potential that some centers opt for the Bridle procedure in lieu of nerve repair.
Continued innovation in novel nerve and tendon transfer techniques, as well as basic science research in
nerve physiology and regeneration will continue to expand treatment options.

One novel strategy under active investigation is the utility of nerve elongation. Based on the observation
that segmental nerve defects requiring cable grafts tend to fare worse than injuries that can be repaired by
primary coaptation, the goal of this strategy is to shorten the nerve gap so that primary repair can be
achieved. For example, knee flexion can facilitate primary coaptation of a segmental CPN defect, and
progressive extension of the knee over several weeks can allow for elongation of the nerve so that full range
of motion can be achieved . Another example would be in the setting of a thigh-level sciatic nerve injury,
[76]
in which a femoral shortening osteotomy can bring the nerve stumps together for primary repair, and then
femor length can be later restored with distraction osteogenesis. Such clinical experiences are anecdotal and
sparsely reported in the literature, but there is growing pre-clinical evidence demonstrating that stretch
forces play an important role in axon elongation and orientation [76-79] . More clinical data is needed to assess
the relative risks and benefits of such strategies against cable grafting.

Other areas of future research should include continued accrual of patient outcome data and comparative
assessments between interventions for complex reconstructions. By nature of the infrequency and
heterogeneity of PNIs, outcomes data for any given procedure is almost universally based on small case
series. Success of motor reconstruction can be measured in terms of strength and range of motion across a
joint in isolation, but to facilitate comparison between interventions it is more meaningful to measure the
performance of compound motions such as assisted vs. unassisted gait, walking on inclined surfaces, and
ability to sit or stand. Continued study of muscular synergies during gait will also help contextualize
reconstructive options as they pertain to restoring functional gait [Figure 2].

In summary, many options have been described for PNIs of variable severity and location, and patients with
what were previously thought to be highly morbid injuries stand to benefit from advanced reconstruction.
Therefore, it is important for orthopedic and plastic surgeons to be aware of the diagnosis, prognosis, and
available reconstructive options for PNIs so that the correct interventions or referrals can be made in a
timely manner.

DECLARATIONS
Authors’ contributions
Made substantial contributions to conception of the article, writing, and editing: Qiu CS, Hanwright PJ,
Khavanin N, Tuffaha S
Performed the cases provided clinical images presented in the article: Tuffaha S
Designed and illustrated figures: Qiu CS