|Program and Abstracts
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Photochemical Tissue Bonding Improves Outcomes for Acellular Nerve Allograft
Neil Fairbairn, MD, Joanna Ng-Glazier, MD, Amanda M. Meppelink, BA, Mark A. Randolph, MS, Ian Valerio, MD, Mark E. Fleming, MD, Robert W. Redmond, PhD, Jonathan M. Winograd, MD.
Massachusetts General Hospital, Boston, MA, USA.
Photochemical tissue bonding (PTB) creates sutureless, watertight bonds between two apposed tissue surfaces that have been stained with photoactive dye and illuminated with a 532nm laser. When applied to nerve repairs wrapped with human amnion, this approach resulted in superior outcomes in comparison to conventional suture fixation. This technique remained efficacious when applied to isograft repair of sciatic nerve injury in a rodent model. Following major injury, demand for autogenous nerve graft may exceed that which can be supplied by the patient. Acellular nerve allograft (ANA) is an option in these circumstances, although outcomes are typically inferior to autograft. This study assesses the efficacy of PTB when used with ANA in a 15mm sciatic nerve gap in the rat.
20 sciatic nerves were harvested from Sprague Dawley rats and sent to AxoGen Inc for processing into ANA. An additional 40 male Lewis rats were randomized into 4 groups (n=10). All rats had 15mm left sciatic nerve defects created and repaired with either isograft or processed ANA. 2 groups had isografts or ANA secured using conventional epineurial suture. The remaining 2 groups had isografts or ANA secured using PTB and amnion. Outcomes were assessed using monthly walking track analysis and sciatic function index (SFI), gastrocnemius muscle mass retention and nerve histomorphometry. Statistical analysis between groups was performed using ANOVA and post hoc Bonferroni all-pairs comparison.
Isograft+PTB recovered the greatest SFI after 5 months. No significant difference in SFI existed between isograft+PTB and isograft+suture. Likewise, ANA+PTB showed greater recovery of SFI in comparison to ANA+suture although this did not reach statistically significant. SFI in both ANA groups was statistically poorer than isograft groups. Isograft+PTB recovered significantly greater muscle mass retention in comparison to all other groups. Although ANA+PTB recovered greater muscle mass in comparison to ANA+suture, this was not significant. Muscle mass recovery was statistically poorer in both ANA groups in comparison to corresponding isograft groups. However, ANA+PTB muscle mass retention was statistically comparable to that achieved using isograft+suture. Distal axon counts were significantly greater for isograft+PTB in comparison to ANA+suture. Isograft+PTB recovered significantly greater fiber diameter, axon diameter and myelin thickness in comparison to all other groups. Recovery was poorest in the ANA+suture group and this was significant in comparison to both isograft groups. Although not significant, ANA+PTB fiber diameter, axon diameter and myelin thickness was greater in comparison to ANA+suture and was statistically comparable to gold standard isograft+suture.
Histomorphometric parameters 5mm distal from distal graft coaptation site (Mean+/-SD)CONCLUSION:
|Experimental Group||Total axon count|
(mm2 x 0.001)
|Nerve fiber diameter (μm)||Axon diameter (μm)||Myelin thickness (μm)||G-ratio|
|* Statistically significant improvement in comparison to isograft+suture||**Statistically significant worsening in comparison|
Photochemical sealing of ANAs results in comparable outcomes to gold standard sutured isografts. If these results translate clinically, this could result in important improvements in peripheral nerve recovery in those cases of severe trauma and limb loss where the use of nerve autograft is not possible. With further refinement, possibly in combination with Schwann cell supplementation, PTB combined with ANA, has the potential to completely supplant the use of autografts following large gap injury.
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