This document summarizes information on nerve allografts for repairing peripheral nerve injuries. It discusses the current gold standard of nerve autografts and limitations such as harvest site morbidity. Nerve allografts and acellularized nerve grafts are presented as alternatives, avoiding donor site issues. Acellularized grafts are harvested from cadavers, decellularized, and stored until use. Several animal and clinical studies show promising regeneration results using acellularized grafts compared to conduits. However, some surgeons remain skeptical and prefer autografts when possible due to lack of long-term data for motor and critical sensory nerves. Both options have pros and cons for different clinical scenarios.

1. Nerve Allografts:
State of the Art
Nickolaos A. Darlis, MD, PhD
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4. Tension reduces blood flow

5. Dealingwiththegap….

6. NERVE AUTOGRAFTING
Gold Standard in setting of a nerve gap
“ Expendable” donors:
• Sensory:
– MABC
– LABC
– Sural
Non‐immunogenic
• Sensory donors do not support motor regeneration
as well as mixed sensorimotor or pure motor nerves
• Motor:
-AIN
-PIN
-Nerve to gracilis

7. NERVE AUTOGRAFTING
the “down side”
• Harvest site morbidity (scarring,
neuroma formation, loss of donor
function)
(20-30% with painful donor site, cold
sensitivity, function alteration )
• Harvest time/cost
• Limited size and length available

8. Long Nerve grafts
• Long nerve grafts highly
successful in only one series
(biceps)
• Prognosis is nerve and site-
specific
• Axillary nerve graft results
mixed, generally 50% effective
• Reduced time to surgery,
shorter grafts associated with
improved outcomes

9. Vascularized nerve grafts
• Vascular pedicled ulnar nerve graft may offer some
advantages in poorly vascularized bed, but no
definitive data to support routine use

10. CONDUITS
• Often used for <3cm gaps in small-diameter sensory
nerves
• Potentially longer with biologic supplementation
• More questions about large mixed nerves
– Mackinnon, 2014 :In my practice, nerve conduits have
largely been replaced by acellularized nerve allografts

11. CONDUITS
the “down side”
• Use limited to small gaps;
– 34%-57% failure rate >5mm gaps
• cost
• lack laminin scaffolding
• lack Schwann Cells, which are crucial to axonal
regeneration
• Semi-rigid material cannot be used around joints

12. CONDUITS
the “down side”
• decreased concentration of neurotrophic factors
associated with larger diameter conduits

13. CONDUITS
the “down side”
• isograft is superior to nerve conduit even with minced nerve
• no significant difference in regeneration among motor,
sensory, or mixed minced nerves

14. NERVE TRANSFERS

15. NERVE ALLOGRAFTS
• taken from ABO blood‐type compatible individuals
– cadaveric
– living related donor
• small diameter nerves
(avoid necrosis of central aspect of nerve from lack of adequate
revascularization)

16. NERVE ALLOGRAFTS
• NERVE ALLOTRANSPLANTATION PATIENT PROTOCOL:

17. NERVE ALLOGRAFTS
• Schwann Cell Migration
• Axonal Growth
• Longitudinal revascularization

18. NERVE ALLOGRAFTS
• Mackinnon, 2014 :”should be reserved for unique
patients with irreparable peripheral nerve injuries,
which, left untreated, would lead to an essentially
nonfunctional limb”

19. ACELLULARIZED NERVE GRAFT
• Harvested from cadavers (Motor
nerves ,no branching)
• Decellularized with detergents
(Hudson et al.)
• Subjected to enzymatic
degradation of CSPGs with
chondroitinase (Neubauer et al.)
• Grafts sterilized with gamma
irradiation
• Stored at ‐80 C

20. Preserved Architecture

22. ACELLULARIZED NERVE GRAFT
• Schwann Cell Migration
• Axonal Growth
• Longitudinal revascularization

23. ACELLULARIZED NERVE GRAFT
• , ,USA
• Guangzhou Zhongda Medical Devices Company, China
loaded with:
– brain-derived neurotrophic factor transfected bone
marrow mesenchymal stem cells
– platelet-rich plasma
– Ginkgo biloba extract

24. ACELLULARIZED NERVE GRAFT
animal study
• Isograft > Acellularized Nerve Graft> Conduit

26. ACELLULARIZED NERVE GRAFT
clinical studies
• RANGER® Study (ongoing)
• Meaningful Recovery (S3-S4 and M3-M5) in 87% of
nerve reconstructions
• No graft-related complications

27. ACELLULARIZED NERVE GRAFT
clinical studies
• MATCH® control arm of RANGER® study (ongoing)
• Outcomes are comparable to nerve autograft and
exceed those for nerve conduit in historical controls.

28. ACELLULARIZED NERVE GRAFT
skepticism
• McKinnon, 2014: “ contraindicated in motor nerve &
critical sensory nerve reconstruction ; autologous
repair with autograft or nerve transfer would always
be my reconstruction of choice in these defects”
• 2013 ASSH, San Francisco, CA: straw poll taken
during allograft nerve session found that the
overwhelming majority of surgeons would prefer
autograft to processed allograft if it were their own
mixed nerve being repaired.

29. N. Tibial
N. Common Peroneal
N. Sciatic

32. • Pros
– Safe (as per studies)
– Single graft repair, no need for multiple cable graft orientation
– Multiple length and diameters (only up to 7cm length)
– Excellent handling properties
– Supporting clinical studies (ongoing)
– Time efficient
– ? Revision
• Cons
– Cost
– Must have a prediction of nerve and gap size
– Logistics ( scheduling, transfer and storage)
– Compromised host?/ previous infection?/ scarred bed?

33. Thank you
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