EXPERIMENTAL INVESTIGATION OF EXPANDED MYOCUTANEOUS FLAPS IN RABBITS

Expansion of the musculocutaneouscutaneous latissimus dorsi (LTD) flap offers the opportunity to pre-elevate a thin and enlarged muscle flap and still have primary closure of the donor site. Our aim was to exam ine in an experimental model the viability, the area of expansion, the contractility and histomorphometry of the muscle as a microsurgical u nit. In eight rabbits, one LTD muscle was slowly expanded using a 30 c c tissue expander which was overexpanded to a volume of 35 cc. The con tralateral LTD muscle served as a control. The area of expansion was m easured radiologically by means of metallic muscle markers implanted o n the muscle fascia. The in vitro muscle contraction, muscle fibre com position and fibre area were determined. The results indicated: 1) the expanded LTD muscle remained richly supplied by its neurovascular ped icle and the transfer as a free flap should be considered. 2) the musc le markers were unstable and thus planimetrical measurements based on the radiographs were invalid. 3) the contractile properties of the exp anded muscle were preserved. 4) histomorphometrical analysis of the cr oss-sections of the expanded LTD muscles displayed no significant redu ction in mean muscle fibre area compared to control fibres. But a sign ificant increase in fast fatigue resistant fibres and connective tissu e was found. Conclusion: Expanded muscles may be used as a microvascul ar unit for dynamic reconstruction. Measurement of the area of expansi on by means of muscle markers placed in the muscle fascia is invalid.