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

Figure 5. Reconstruction algorithm for complete sciatic nerve injuries.

from surgical positioning or orthopedic procedures of the knee. Injury to the CPN results in characteristic
foot drop and sensory deficits of the dorsal foot. Untreated, this results in a varus deformity and steppage or
foot-slapping gait.

For axonotmetic injuries (Sunderland II-IV), based on the clinician’s cumulative assessment of the history,
exam, electrodiagnostic and imaging findings, the rate of full spontaneous recovery ranges from 76% to 87%.
However, in cases where spontaneous improvement is not evident after four months or if complete injury is
suspected, surgical intervention is indicated [Figure 6] [46,47] . In a review of 1577 CPN repairs, George and
Boyce reported that good outcomes, defined as MRC 4 or better, were observed in just 45% of cases.
[48]
Outcomes were better in injuries that only required neurolysis (80% good outcomes), namely entrapment or
compression injuries. Individual reports of CPN injuries requiring end-to-end repair or interpositional
grafting (lacerations or stretch-avulsion injuries) have claimed as high as 84% good outcomes, but the
literature aggregate is only 37% . A criticism of this study is that method of management is confounded by
[41]
the mechanism and severity of injury, and criteria for choice of management are not clear. In general, we
posit that the mechanism and severity of injury are major determinants of outcomes; clean lacerations and
compression injuries tend to do well (60%-85% good outcomes), while traction and high-energy trauma fare
poorly (30%-50% good outcomes). The length of nerve graft is also a major determinant of outcomes, with
[48]
the percentage of patients achieving good outcomes decreasing to 29% from 64% grafts exceeded 6 cm .
Few surgeon-modifiable levers are available other than expediting time to intervention.

Some have hypothesized that vascular insufficiency is a limitation to conventional nerve grafts for CPN
reconstruction, so vascularized nerve grafts have been attempted. Terzis and Kostopoulos performed 12
[49]
vascularized nerve grafts (medial and lateral sural nerves) for CPN defects ranging from 4 to 18 cm gaps. An
impressive two-thirds of their patients with graft length greater than 13 cm demonstrated dorsiflexion
against gravity, but they lacked a comparison cohort of patients with conventional grafts. Furthermore, the
vascularized nerve grafts shorter than 13 cm actually performed worse than the comparator set of
conventional grafts. A recent review of vascularized nerve grafts concludes that there is evidence suggesting
better blood supply and enhanced nerve regeneration, but there are few clinical scenarios where that
difference is meaningful . No studies demonstrate compelling evidence for their superiority over
[50]
conventional grafts. For these reasons as well as the added complexity of the procedure, vascularized nerve