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Evaluation of Peripheral Nerve Perfusion and Recovery in Tensioned Repairs
Matthew Weber, MD
1, Mohamed Abdelrahman, MD
1, Kriston Seward, BS
1, Geetanjali Bendale, PhD
1, Taylor Allen, BS
1; Jonathan Isaacs, MD
2(1)Virginia Commonwealth University, Richmond, VA, (2)Department of Orthopaedics, Virginia Commonwealth University, Richmond, VA
Nerve repairs under tension yield poor outcomes, with experimentally demonstrated decreases in axon regeneration. No study has previously quantified nerve perfusion in surgically repaired nerves. We hypothesize that primary nerve repairs completed under tension will exhibit decreased nerve blood flow compared to non-tensioned repairs, and this decreased blood flow will correlate with impaired nerve regeneration.
Thirty Lewis rats underwent bilateral sciatic nerve exposure, with the left sciatic nerve mobilized, transected, and repaired across 0mm, 4mm, or 8mm defects. Laser doppler flowmetry was used to assess nerves exposed, mobilized, and immediately after primary suture repair. Measurements were then repeated at five, ten, and thirty minutes post-repair. Twelve weeks were allowed for nerve regeneration. Bilateral nerves were again exposed, doppler measurements were obtained, and testing of bilateral gastrocnemius muscle strength was performed. Muscles and nerves were then harvested for evaluation of muscle size and axon counts. Statistical analysis of variance was performed comparing cohorts of rats in each testing condition to evaluate for significant changes between cohorts and within each cohort over time.
Immediately after repair, the 4mm group exhibited significantly decreased perfusion relative to the 0mm group (p=0.02), and the 8mm resection group exhibited significantly decreased perfusion relative to both the 0mm and 4mm groups (p<0.001 and p=0.013, respectively). Similar results were observed at ten and thirty minutes post-repair. At twelve weeks, all experimental nerves exhibited increased perfusion relative to control nerves, with no significant differences between groups. There were no significant differences in muscle mass, muscle girth, contraction strength, or axon counts between cohorts.
The data support an inverse relationship between the size of nerve defect and blood flow after repair, implying an association between tension and impaired tissue perfusion. Each cohort demonstrated similar reconstitution of perfusion at 12 weeks. In conjunction with muscle and axon data which did not reveal statistical differences between groups, these findings may suggest some tolerance for transient ischemia. This experiment validates a reproducible method for measuring the effect of tension management on nerve perfusion and regeneration. This is the first study to quantify nerve perfusion in surgically repaired nerves.
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