title: To reverse or not to reverse? A systematic review of autograft polarity on functional outcomes following peripheral nerve repair surgery.
abstract: BACKGROUND
  The literature describing the best clinical practice for proximal-distal autograft orientation, otherwise known as nerve graft polarity, is inconsistent. With existing disparities in the peripheral nerve literature, the clinical question remains whether reversing nerve autograft polarity bears an advantage for nerve regeneration.
  
  
  METHODS
  A comprehensive review of the literature using Embase and PubMed databases (1940-June 2015) was performed to retrieve all original articles on the effects of nerve autograft polarity on nerve regeneration and functional recovery following primary repair of peripheral nerve defects.
  
  
  RESULTS
  The initial database search yielded 318 titles. Duplicate exclusion, title review and full text review yielded six articles which directly compared nerve autograft polarity. Histological, morphometric, electrophysiological, and behavioral outcomes were reviewed. All retained articles were animal studies, of which none demonstrated significant differences in outcomes between the normal and reversed polarity groups. A reversed graft may ensure that regenerating nerve fibers are not lost at branching points, however this may not translate into improved function.
  
  
  CONCLUSIONS
  There is insufficient data to suggest that nerve autograft polarity has an impact on nerve regeneration and functional outcomes.
authors.affiliation: Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.|Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, Pennsylvania.
authors.forename: S E
authors.identifier: http://orcid.org/0000-0001-7885-8574
authors.initials: SE
authors.lastname: Roberts
authors.affiliation: Division of Plastic Surgery and Department of Orthopedic Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: S
authors.initials: S
authors.lastname: Thibaudeau
authors.affiliation: Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.|Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, Pennsylvania.
authors.forename: J C
authors.initials: JC
authors.lastname: Burrell
authors.affiliation: Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: E L
authors.initials: EL
authors.lastname: Zager
authors.affiliation: Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.|Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, Pennsylvania.
authors.forename: D K
authors.initials: DK
authors.lastname: Cullen
authors.affiliation: Division of Plastic Surgery and Department of Orthopedic Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: L S
authors.initials: LS
authors.lastname: Levin
mesh_terms: D064592:Autografts / Q000601:surgery*; D006801:Humans; D009416:Nerve Regeneration / Q000502:physiology; D059348:Peripheral Nerve Injuries / Q000601:surgery*; D019651:Plastic Surgery Procedures / Q000379:methods; D020127:Recovery of Function; D014182:Transplantation, Autologous / Q000379:methods*; D016896:Treatment Outcome