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Figure 1. Rule-of-thumb calculation for predicting outcomes after neurorrhaphy. Assuming that axonal regeneration occurs at a rate of
2.5 cm per month and that the neuromuscular junction will remain intact for 18 months, favorable neurorrhaphies are those in which the
distance between the injury site to the muscle target is less than 45 - 2.5x in centimeters, where x is the number of months since injury.
In example 1, primary repair at 6 months after high sciatic nerve injury is unfavorable and nerve transfers should be considered. In
example 2, primary repair at 9 months of a low sciatic nerve injury is favorable.

restored. Again, the regeneration distance and timing of intervention should be such that the reinnervation
[26]
of the target muscles occurs expeditiously to maximize motor recovery .
Finally, when nerve reconstruction or distal nerve transfers cannot be expected to produce meaningful
functional recovery for the consideration discussed above, tendon transfers can be considered. The
following sections describe complex nerve and tendon transfers for functional reconstruction of specific
nerves in the lower extremity.

Reconstruction of femoral nerve injury
Injury to the femoral nerve results in deficits of hip flexion, knee extension, and sensation to the
anterolateral thigh and leg. Generally, hip flexion is largely preserved due to activity of the iliopsoas, which
is innervated by the lumbosacral plexus, but knee extension is severely impacted. In the gait cycle, knee
extension is most important in preparation for heel strike and into early stance as it stabilizes the knee while
the body’s center of gravity lies posterior to the joint axis [Figure 2]. Even when a patient has satisfactory
gait on a flat surface, patients with quadricep weakness may still have difficulty with stairs, inclines, and
standing from a chair. Therefore, the goals of reconstruction are to stabilize the knee and restore forceful
knee extension to enable walking and transferring from a seated position.

Our approach to femoral nerve reconstruction depends primarily on the availability of proximal and distal
nerve stumps, the length of the defect, and the amount of time that has elapsed since injury [Figure 3]. In
general, repair of the nerve with or without grafts should be considered when timely intervention is
possible, because regeneration distances are relatively short in the thigh. However, in many scenarios,
including delayed repair, large segmental defects, or very proximal nerve injury (i.e., retroperitoneal tumor
resection), nerve transfers offer the best chance for meaningful functional recovery. When available, the
obturator nerve offers the best donor nerve to address femoral nerve injuries, with ample length to achieve
[27]
tension free end-to-end or supercharged end-to-side transfers . As described in 2010 by Campbell et al. ,
[28]
the obturator to femoral nerve transfer has since been utilized, modified, and described many times in the
literature with good consistency of outcomes, typically achieving MRC grade 4 or better [28-31] . The technique
usually involves transferring the gracilis branch to a large motor division supplying the rectus femoris and