American Society for Peripheral Nerve

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Peripheral Nerve Repair with Amnion-Muscle Combined Conduits
Stefania Raimondo, PhD1; Andrea Marchesini, MD2; Nicola Zingaretti, MD3; Bruno Battiston, MD, PhD4; Stefano Geuna, MD5; Michele Riccio, MD2
1University of Torino, Orbassano, Torino, Italy; 2A.O.U. Ospedali Riuniti di Ancona, Ancona, Italy; 3University of Udine, c/o Ospedale "S. Maria della Misericordia", Udine, Italy; 4UO di Microshirurgia Ricostruttiva, Hand Surg., Microsurg. Unit, Torino, Italy; 5Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Torino, Italy

Introduction Peripheral nerve injury remains a significant clinical challenge in reconstructive microsurgery because it is a relatively common consequence of trauma, diseases, or tumor surgery. The amnion-muscle combined conduits allows to obtain good clinical results in peripheral nerves gap repair. It consists in the combination of the human amniotic membrane conduit filled with autologous skeletal muscle fibres harvested in the site of nerve lesion.   These results seem to be due to the biological characteristics of human amniotic membrane that can be reassumed in: pluripotency of amnion-derived cells, anti-inflammatory and low immunogenic characteristics of amniotic membrane/amnion-derived cells, non-tumorigenicity and little ethical problems with usage.  The purpose of this study is to evaluate the final outcome of nerve regeneration, both morphologically and functionally, across the amnion-muscle combined conduits in comparison with nerve autograft that it still is the gold standard of nerve gap reconstruction.

Materials and methods Fourteen male Wistar rats were divided into two groups: 1.5 cm length gap on median nerve reconstructed by means of i) a reverse nerve autograft; ii) amnion-muscle combined conduits. Functional results were evaluated at 30, 60 and 90 days post-operatively, performing grasping test. Morphological and stereological analysis were performed on the samples collect 90 days post-operatively using high resolution light microscopy examination and design-based stereology.

Results Our results showed that amnion-muscle combined conduits used for repairing a rat median nerve allowed nerve fibres regeneration and functional recovery.  Functional recovery, evaluated using grasping test 30, 60 and 90 days after surgery, was observed in both groups, even if amnion-muscle combined conduits group showed significantly lower values that autograft group throughout the post-operative period. Moreover, the stereological analysis showed that, in amnion-muscle combined conduits group, regenerating median nerves have significantly more myelinated fibres with the same axon size, but significantly thinner myelin than autograft group. These values lead to have significantly smaller myelinated nerve fibres and a significantly higher g-ratio in the amnion-muscle combined conduits group.

Conclusions Though the autograft remains the gold standard treatment to restore wide nerve gap, the amnion-muscle combined conduit has proved to be effective in allowing nerve regeneration through a critical rat's nerve gap of 15mm, these findings support, with an experimental observation, the great clinical results obtained using AMCG conduit to restore traumatic nerve's gap wide from 3 to 6 cm of sensitive forearm nerves that we previously published2 confirming the great regenerative value of amniotic membrane.

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