Nerve Connectors Applied to Allograft Repairs Only Effective Across Small Gaps
Jonathan Isaacs, MD1; Satya Mallu, MD1; Amy Kite, MD2; Sagar Shah, MD3; Gaurangkumar Patel, B.S.2
1Division of Hand Surgery, Department of Orthopaedic Surgery, Virginia Commonwealth University, Richmond, VA, 2Virginia Commonwealth University, Richmond, VA, 3Louisiana State University, New Orleans, LA
Introduction: Nerve connectors are short nerve conduits used to approximate nerve ends and can affect a primary repair even across a few millimeter gap. Acellular nerve allografts are viable alternatives when direct repair is not possible. We hypothesize that acellular nerve allograft implanted using nerve connectors at the repair sites must have end to end contactwith the in-situ nerve stumps to support nerve regeneration.
Materials & Methods:
Sixty (three-month old) Sprague-Dawley rats underwent a 14mm unilateral tibial nerve injury and subsequent repair using various combinations of acellular nerve grafts and nerve connectors. Proximal repairs for all groups utilized direct contact with the nerve stump within a 4mm connector. Variations in distal repair methods (allograft length, nerve gap, and connector length) defined our four groups (N=15 for all groups): Group A: 14mm allograft, no distal gap, and 4mm distal connector; Group B: 11.5mm allograft, 2.5mm distal gap, and 6.5mm distal connector; Group C: 9mm allograft, 5mm distal gap, and 9mm distal connector; Group D: 14mm allograft, no distal gap, and no distal connector.
At three months post-repair, function and histomorphology were assessed.
Developed muscle force was significantly lower in Group C (0.073±0.077N) compared to the other three groups (Group A=0.529±0.312N, Group B=0.461±0.462N, Group D=0.409±0.327N).
Axon counts were significantly lower in Group C (2121 ± 389) compared to Group A (6401 ± 855), Group B (4710 ± 755) and Group D (4450 ± 126). There was no statistically significant difference in G-ratios between groups (p>0.05).
Conclusion: Nerve regeneration was significantly impaired as gap distance between the distal end of the allograft and the distal nerve stump increased to 5mm. Peripheral nerve surgeons should be aware of the potential compromise of outcomes with gaps of more than 2.5mm millimeters when using nerve connectors in conjunction with nerve allograft.
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