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Page 2 of 17 Qiu et al. Plast Aesthet Res 2022;9:19 https://dx.doi.org/10.20517/2347-9264.2021.126

INTRODUCTION
Peripheral nerve injuries (PNI) in the lower extremity are an uncommon but highly morbid condition,
usually resulting from traumatic or iatrogenic injury. In the civilian trauma setting, PNIs occur in 1.8%-2.8%
of extremity injuries, of which 23%-40% are of the lower extremity . Injuries to the peroneal and sciatic
[1,2]
nerves are the most common, accounting for more than two-thirds of cases. In the modern military setting,
the relative incidence of tibial nerve injuries increases to match that of peroneal nerve injuries, likely
[3]
reflecting the impact of improvised explosive devices causing a broader zone of injury . Beyond trauma, the
incidence of iatrogenic nerve injury should not be underestimated, accounting for 10%-17% of all PNIs,
including those in the lower extremities . Timely recognition and management PNIs are the primary
[4,5]
[6]
barriers to better outcomes .
Many factors differentiate nerve reconstruction in the lower vs. upper extremity. First, the nature of lower
extremity injuries tends to be more severe, often resulting in large segmental nerve defects. Second,
regenerative distances can be much greater with few donor nerves available for distal transfers. Finally, the
goals of nerve reconstruction in the lower vs. upper extremities differ in a number of ways. Unlike the upper
extremity, where dexterity and fine discriminiative sensation are valued, reconstruction of the lower
extremity prioritizes the restoration of stable, painless gait and protective sensation. Historically, nerve
reconstructions were rarely performed because little was known about how to accurately diagnose and
surgically manage these injuries . However, recent advances in our understanding of nerve physiology and
[7-9]
microsurgical techniques have inspired renewed faith in nerve surgery and sparked a creative renaissance in
the tools, approaches, and reconstructive schemas available to surgeons in the management of lower
extremity PNIs.

The optimal reconstructive strategy for PNIs often depends on what is observed during the exploration of
the injured nerve. A broad understanding of the available interventions facilitates successful pre-surgical
planning, patient counseling, and intra-operative decision-making. In this review, we provide a principles-
based approach for the surgical management of lower extremity nerve injuries with an emphasis on
techniques for functional reconstruction after complete nerve injury.

DIAGNOSIS AND EVALUATION
Outcomes are highly dependent on the timeliness and accuracy of diagnosis. History-taking should
determine the timing and mechanism of injury, rapidity of onset of symptoms, and functional deficits.
Open injuries with acute onset of numbness or weakness are typically explored and repaired immediately,
particularly when concomitant vascular, orthopedic or soft tissue injuries require immediate surgical
intervention. Crush or high-energy injuries are associated with a wide zone of nerve injury and should be
explored in a delayed manner to allow the extent of tissue damage to declare. Depending on the rapidity of
onset, progressive weakness suggests a compression neuropathy from mass effect (e.g., tumor or
hematoma), muscular or ligamentous compression, or osmotic edema (e.g., diabetes). The degree and
distribution of functional loss will hint at the degree of injury to nerve architecture (neuropraxia vs.
axonotmesis vs. neurotmesis) as well as localization of the lesion. Finally, the history should also identify
any patient characteristics or comorbidities that may affect outcomes, such as their self-efficacy and alacrity
for rehabilitation, prior surgeries or radiation that may render a less favorable tissue bed, diabetes,
peripheral vascular disease, and smoking. The patient’s age is an important consideration that will influence
surgical decision making, as regenerative potential is known to decline with age.