Functional outcome after facial allograft transplantation in rats

Full face, hemiface and facial subunit transplants have been reported before. However, the functional recovery of the face transplant largely remains unknown. The mystacial pad (also known as the vibrissal or whiskers region) is the main sensorimotor unit in rats' faces. We included the mystacial region in the hemifacial flap of the rat, and our aim was to study its functional recovery after transplant.

Hemifacial flaps were transplanted from Brown-Norway RT(n) to Wistar-Lewis RT(l) rats, under tapered doses of tacrolimus immunosuppression monotherapy (8 mg/Kg/day to 2mg/Kg/day after 4 weeks). Group I (n=12) was the anatomic study group, in which the harvesting technique of the flap was trial run and angiographies of the flap were obtained. In group II (n=12), non-vascularized hemifacial allografts were transplanted. Group III (n=24) was the vascularized hemiface allotransplant group. This was divided into two subgroups relating to nerve repairs. In subgroup III(a) (n=12) no nerve repairs were performed, while in subgroup III(b) (n=12) the zygomaticoorbital, bucolabial and upper marginal mandibular branches of the facial nerve, and the infraorbital branch of the trigeminal nerve were repaired. Clinical, neurophysiological and histological studies were performed to evaluate the recovery of the mystacial region after six weeks.

In group I the hemifacial flap harvesting technique to include the mystacial region was established, and angiographies confirmed a rich axial vascular network in the flaps. All grafts in group II necrosed. In group III, each procedure required an average of 7h (range 5-11). Of this group, 75% of the rats survived for 8 weeks. In subgroup III(a) no signs of recovery were noted, whilst in subgroup III(b) clinical, neurophysiological and histological recovery were found in face transplant recipients after 6 weeks.

The hemifacial flap including the mystacial region could be transplanted successfully in the rat model. Face allotransplants in which nerves were repaired showed clinical, neurophysiological and histological signs of recovery.