[Free functional muscle transplantation for facial reanimation: experimental comparison between the one- and two-stage approach].
To investigate functional results of either one- or two-staged free muscle transplantation, the scutuloauricularis model in the New Zealand white rabbits was used. 30 rabbits were divided into 2 groups with 15 animals each. In group 1 (one-stage approach) the peroneus brevis (PB) muscle was harvested as a free muscle graft with a 7-cm long motor branch. The graft was positioned in the place of the right scutuloauricularis (SCUT) and its vascular supply microsurgically re-established. The motor branch was transferred to the contralateral side and its proximal end coapted to the cut facial motor branch to the left SCUT. Before nerve coaptation, biopsies were harvested from the cut motor branch for morphological analysis. In group 2 (two-stage approach) a 7-cm long saphenous nerve graft was taken and coapted to the cut motor branch of the SCUT and crossed over to the contralateral side. Nerve specimens from the cut motor branch were taken. Eight months later, free transplantation of the PB was performed and its motor branch coapted to the distal end of the cross-over nerve graft. After a total time period of 13 months the final experiments were carried out in each group. Maximal tetanic tensions in the reinnervated PB were measured and biopsies of muscle grafts together with nerve biopsies from the distal part of the motor branch were harvested for morphological analysis. Muscle grafts of group 1 revealed tetanic tension values of 12.5 N (SD 3.1) in comparison to 10.6 N (SD 3.5) obtained in group 2. This difference was not statistically significant (p = 0.303). In group 1 the amount of regenerated nerve fibres counted at the distal motor branch site (mean: 2798, SD 1242) was significantly higher (p = 0.008) than in group 2 (mean: 1138, SD 1004). Muscle graft morphology revealed significantly less type I fibres (p = 0.016) and more type II b/d fibres (p = 0.011) in group 1 compared to group 2. However, the overall amount of perimysial connective tissue showed no significant difference in both groups (p = 0.478). Free muscle transplantation in a one-stage approach offers similar functional results in comparison to the two-stage approach. Although muscle grafts of the one-stage transplantation underwent a longer period of denervation, similar contents of perimysial connective tissue could be observed. Georg Thieme Verlag KG Stuttgart, New York.