Morphometric changes in free neurovascular latissimus dorsi flaps: an experimental study

This study was designed to investigate regeneration of reinnervated, free transplanted muscles. We used a rat model, consisting of eight rats per group, in which the latissimus dorsi muscle was transplanted orthotopically and then harvested and evaluated after 2 and 12 weeks. Age-matched control animals were used to oppose non-operated muscles. At date of removal the patency of the vascular anastomoses was checked clinically and histologically. Electrophysiological measurements were also performed and conventional and enzyme histochemical histological slides manufactured. Two weeks after the free neurovascular flap transfer the muscle was not yet innervated, and histologically a dissolved pattern of type 1 and type IIA muscle fibres was found. The muscle fibres demonstrated a decrease of more than 50% cross-sectional area. After 12 weeks the muscles were reinnervated again; muscle contraction was positive with electrical stimulation and the cross-sectional area had regained 80% of the activity of normal muscle fibres. With enzyme histochemical staining the typical type grouping of reinnervated muscles could be demonstrated.