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Buncke. Plast Aesthet Res 2022;9:38 https://dx.doi.org/10.20517/2347-9264.2022.08 Page 11 of 17

(suture of digital nerve, hand, or foot, 1 nerve), 64911 (nerve repair with autogenous vein graft), 64999
[82]
(unlisted procedure nervous system) and 64834 (suture of 1 nerve, hand, common sensory nerve) .
Additionally, the surgical algorithm for peripheral nerve repair has continued to be updated, as recently
updated algorithms incorporate the use of engineered nerve allograft as well as autograft in gaps up to 7 cm
in length [83,84] . The clinical evaluation of 22 nerve repairs using engineered nerve allograft in 2019 showed
meaningful motor recovery, as noted by M3 function or above, in 73% of nerve repairs with a median of 33
± 17 mm (10-70 mm) for nerve graft lengths . Furthermore, motor recovery of M3 or above was reported
[72]
[72]
at 80% for nerve gaps 10-25 mm, 63% for nerve gaps 26-49 mm, and 75% for nerve gaps 50 mm or larger .
While this was a small cohort, additional larger studies provided similar evidence. In 2020, Safa et al.
reported on meaningful recovery, defined as S3/M3 or greater, in 624 sensory and mixed nerve gap repairs
[74]
measuring up to 70 mm in length . Safa and colleagues showed that in gap lengths 50-70 mm, repair with
Avance nerve graft resulted in 69% meaningful recovery, with no statistical difference between the 50-70
[74]
mm, 30-49 mm, and 15-29 mm nerve gap repair groups . Furthermore, there was an overall meaningful
recovery of 82% in nerve gaps up to 70 mm in length, which was noted to be comparable to historical data
[74]
for nerve autograft and exceeding historical literature for conduit .
While a plethora of positive clinical evidence has been presented for the use of engineered nerve allografts,
additional literature has been published with lower success rates. In 2019, a case series of three patients was
presented by Nietosvaara outlining poor results due to engineered nerve graft resorption ; however, the
[71]
failures were attributed to possible infection and host rejection. In 2020, Leckenby et al. presented sub-
optimal results for a single-center experience with engineered nerve allograft and found that 77% of patients
achieved sensory recovery of S3 or better and 36% of patients achieved motor recovery of M3 or better .
[73]
However, Leckenby et al. suggested that outcomes with the engineered nerve grafts were similar to nerve
autograft in short nerve gaps . Further discussion by Leckenby et al. suggested that issues were
[73]
[73]
encountered with increased length and diameter of engineered nerve grafts .
When considering the body of evidence for the clinical use of engineered nerve grafts for the repair of
peripheral nerve defects, there is overwhelming support for their application. Furthermore, the use of
engineered nerve grafts can also circumvent the comorbidities associated with nerve autograft. With these
considerations, there is sufficient support for further clinical use of engineered nerve allografts, such as
Avance nerve graft.

DISCUSSION
Peripheral nerve repair, much like other surgical repairs, has undergone a drastic transformation in the last
20 years. This transformation has been largely in part due to the development of innovative peripheral nerve
repair materials such as nerve conduits and engineered nerve allografts. Nerve conduits have provided a
material to improve peripheral nerve repair by providing a protected environment for peripheral nerve
regeneration, moving the suture away from the regenerating axons at the proximal nerve stump, and
allowing for selective reinnervation of the distal target . While these advances in the application of nerve
[81]
conduits have been useful, the application of a nerve conduit should be limited to nerve gaps less than 1 cm
[47]
in length . Longer nerve gaps require the use of a nerve autograft or engineered nerve allograft. While
nerve autografts have shown good outcomes in large gaps, the patient comorbidities associated with nerve
autograft harvest often include chronic pain, wound infections, wound complications, and sensory
deficits . While recovery from some of these complications may occur, sensory deficits have shown
[43]
variable outcomes, with 0%-11% of adult patients experiencing complete sensory recovery . The variability
[43]
in recovery of sensory deficits has been suggested to be correlated with the length of the resected nerve
segment, where longer nerve segment resections, such as nerve autograft harvest, show larger areas of