Abstract Clinical data have shown that a vein segment filled with fresh skeletal muscle can be considered a good autologous grafting conduit for the repair of pe- ripheral nerve lesions. In this study, the long-term mor- phological organization of rat sciatic nerve fibers regen- erated along a muscle-vein-combined graft conduit is further analysed by light and electron microscopy. Re- generated nerve fibers were organized into fascicles of various sizes that were clearly delimited by perineurial- like shells made by long and thin cytoplasmic processes of perineurial-like bipolar cells and by densely packed collagen fibrils. Grafted skeletal muscle fibers were still detectable among nerve fiber fascicles. However, in spite of the persistence of skeletal muscle along the graft, re- generated nerve fibers showed a good morphological pattern of regeneration, providing further evidence that the muscle-vein-combined grafting technique represents an effective surgical alternative to the classical fresh nerve autograft for the repair of peripheral nerve defects. Key words Nerve repair · Nerve fiber regeneration · Sciatic nerve · Muscle-vein-combined graft · Rat Introduction Although autogenous nerve grafting is still considered the best current method for bridging peripheral nerve le- sions with substance defect (Terzis et al. 1997), several other grafting conduits (i.e., biological or synthetic tubes) have been studied experimentally for nerve repair (Lundborg et al. 1981; Glasby et al. 1986; Jimming et al. 1986; Brunelli et al. 1987; Rich et al. 1989; Mackinnon and Dellon 1990; Chen et al. 1994; Ansselin et al. 1997). Previous studies showed that a new surgical procedure, named muscle-vein-combined grafting technique, could give very good results even for the repair of long- distance nerve defects (Brunelli et al. 1993; Battiston et al. 2000a,b). This type of autologous graft is repre- sented by a vein filled with fresh skeletal muscle, with- drawn in the site of surgery, that is sutured to bridge the two stumps of a severed nerve. Clinical application of this surgical technique led to good nerve repair, both for motor and sensory nerves, with satisfactory functional recovery in 85% of patients (Battiston et al. 2000a). This autologous grafting technique, unlike fresh nerve auto- graft, does not produce the secondary damage due to the withdrawal of a healthy sensory nerve and does not pres- ent any limitation in the availability of graft material (veins and skeletal muscle) in the site of the lesion. In addition, the combination of muscle and vein for nerve grafting allows going beyond the length limitations of other tubulization techniques (Battiston et al. 2000a,b), such as those using vessels or skeletal muscle alone, since empty vein tubes collapse in long gaps (Chiu et al. 1990) whilst relevant axon dispersion may occurr in grafts made by muscle alone (Mackinnon and Dellon 1990). Previous morphometrical investigation in the rat sci- atic nerve (Battiston et al. 2000b) showed that, six months after surgery, quantitative data on number and size of myelinated nerve fibers are similar to those previ- ously reported for direct nerve repair (Mackinnon et al. 1991). Surprisingly, the persistence of some muscle fi- bers was detected at this stage post-operatively. In the light of the very promising results, both exper- imental and clinical, obtained by the muscle-vein- combined grafting technique, the present study aimed at further investigating the long-term morphological orga- nization of nerve fibers regenerated along this type of graft. S. Geuna ( ✉ ) · R. Guglielmone · M.G. Giacobini-Robecchi Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Ospedale San Luigi, Regione Gonzole 10, 10043 Orbassano (TO), Italy e-mail: geuna@sluigi.unito.it Tel.: +39-011-6708135, Fax: +39-011-9038639 P. Tos · B. Battiston Gruppo Interdivisionale di Microchirurgia (G.I.M.), Ospedale C.T.O., Torino, Italy Anat Embryol (2000) 201:475–482 © Springer-Verlag 2000 ORIGINAL ARTICLE Stefano Geuna · Pierluigi Tos · Bruno Battiston Renzo Guglielmone · Maria G. Giacobini-Robecchi Morphological analysis of peripheral nerve regenerated by means of vein grafts filled with fresh skeletal muscle Accepted: 14 December 1999