THE MESH REPAIR: TENSION FREE ALTERNATIVE ON DEALING WITH NERVE GAPS—EXPERIMENTAL RESULTS PAULO ROBERTO KECHELE, M.D., 1 * JAYME AUGUSTO BERTELLI, Ph.D., 2 EDUARDO MONGUILHOTTI DALMARCO, M.D., 3 and TA ˆ NIA SILVIA FRO ¨ DE, Ph.D. 4 We evaluated the feasibility of external epineurial splinting as a way of alleviating tension caused by sutures in the reconstruction of peripheral nerve injuries, utilizing Wistar rat median nerve injury on 40 animals, in four experimental groups with 10 animals on each surgical setting. The nerve regeneration outcomes of four surgical procedures were compared: 1) primary end-to-end sutures (EES); 2) alleviated tension sutures (ATS) with a removal of 7 mm nerve segment, namely external epineurial splinting, utilizing a polypropylene mesh as a protective scaffold; 3) sutures under tension with a 7 mm gap between nerve stumps; and 4) sham (C) (n 5 10 animals). Regeneration of the median nerve postneurorrhaphy was followed by means of functional evaluations, including time to first day of finger flexion recovery, and grasp strength; quantification of atrophy of the flexor pronator muscle group; and mRNA expression of nerve growth factor and neurotrophin-3 by polymerase chain reaction-reverse transcriptase. Similar, significant median nerve regeneration was observed in the EES-treated and ATS-treated groups, relative to controls. The EES and ATS surgical procedures methods demonstrated important similar results considering functional and molecular biology analysis of the median nerve injury. V V C 2011 Wiley-Liss, Inc. Microsurgery 31:551–558, 2011. End-to-end suturing is the gold standard for the repair of peripheral nerve injuries. 1,2 However, this is not always possible. Retraction of the axotomized nerve ends usually precludes direct approximation within a few days or weeks of the trauma, requiring the use of nerve grafts to repair the defect. 3–5 The standard approach to repair a peripheral nerve when a gap is present is to bridge the severed ends with a segment of autologous donor nerve. When the caliber of the donor autograft matches that of the recipient nerve, in both total diameter and average axon density, superior results are obtained. 6 Entubulation repair, by which the proximal and distal ends of the severed nerve are inserted into either end of a hollow conduit, has been attempted extensively. 7,8 It is hypothesized that isolation of the local regenerative milieu may encourage more focused regeneration toward the distal stump. With a few chronic injuries, traction applied to the nerve stumps during surgery, aided by delicate forceps, restores nerve contact. However, the elastic properties of nerves tend to separate the stumps. When this force of nerve stump separation is greater than the physiologic threshold, excessive tension is created at the suture line impairing nerve regeneration, which leads to poor outcomes. 9,10 How- ever, it is uncertain whether nerve grafting is necessary when end-to-end repair would result in only mild to moder- ate tension, as well as what is the length of the nerve gap that should be corrected by direct coaptation. 11,12 We have hypothesized that, when nerve loss occurs in which the stumps can be approximated by traction, an external epineurial splint can inhibit the deleterious effects of tension on the suture line, as a tension free repair. An ideal epineurial splint is one that is applied in accordance with Saint-Venant’s principle, which states that, if traction is applied to the rim of an elastic cylin- der, a nonuniform strain is produced at the tip of that cylinder; however, if traction is applied distal to the rim, a uniform stress is produced at the cylinder tip. 13 In these experiments, we analysed the regeneration of the rat median nerve and repaired it using either: a) an alleviated tension suture (ATS) following segmental nerve removal; b) an end-to-end suture (EES); or c) a suture under tension (SUT). We compared functional results in these three treatment groups, related to controls. In addition to comparing functional outcomes, we were interested in the effects of these different reconstructive procedures on mRNA expression levels of nerve growth factor (NGF) and neurotrophin-3 (NT-3). MATERIALS AND METHODS Animals The study was approved by the Committee for Ethics in Animal Research of the Federal University of Santa Catarina. Forty adult male Wistar rats, between the ages of 12 and 14 weeks old and weighing roughly 220 g, were used for the experiments, 10 animals in each of four 1 Departamento de Clı ´nica Ciru ´ rgica, Centro de Cie ˆncias da Sau ´ de, Universi- dade Federal de Santa Catarina, Trindade, Floriano ´ polis, SC, Brazil 2 Centro de Cie ˆncias Biolo ´gicas e da Sau ´de, Universidade do Sul de Santa Catarina (Unisul), Tubara ˜o, SC, Brazil 3 Departamento de Cie ˆ ncias Farmace ˆuticas, Centro de Cie ˆncias da Sau ´de, Universidade Regional de Blumenau, Itoupava Seca, Blumenau, SC, Brazil 4 Departamento de Ana ´lises Clı ´nicas, Centro de Cie ˆncias da Sau ´ de, Universi- dade Federal de Santa Catarina, Trindade, Floriano ´ polis, SC, Brazil *Correspondence to: Paulo Roberto Kechele, Departmento de Clı ´nica Ciru ´rgica, Centro de Cie ˆncias da Sau ´de, Universidade Federal de Santa Catarina, Trindade, 88040-970 Floriano ´polis, SC, Brazil. E-mail: pkechele@gmail.com Received 6 October 2010; Revision accepted 28 February 2011; Accepted 3 March 2011 Published online 31 May 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/micr.20902 V V C 2011 Wiley-Liss, Inc.