Moderators of angiogenesis in muscle flaps: A non-randomised animal study

Abstract

A muscle flap can survive a pedicle injury under favourable conditions. In the reconstruction of compound limb injuries, the wound milieu is variable and may affect the rate and manner of neovascularisation. Our aim is to determine the effect of some key clinical variables on neovascularisation in muscle flaps in an animal model. The pectoralis profundus was raised in 60 rats and covered with a skin graft. Fifteen rats were allocated to each of the following groups: separation of the flap from the skin inset (S), inflammation by inoculation with Staphylococcus aureus (I), flap elevation with harmonic scalpel (H) and preservation of the motor nerve (N) as well as compared to controls (C). Graft take and wound complications were assessed five days later, as well as perfusion before and after pedicle ligation, by laser Doppler flowmetry and neovascularisation using barium angiography. Flaps with an intact motor nerve had significantly higher graft take than controls (59% vs 29%). Perfusion change was lesser in all study groups than in controls, although the extent of flap necrosis was not significantly different. Only flaps raised with the harmonic scalpel generated more new vessels than controls at the inset (9.6 vs 3.2), particularly at the origin of the muscle (1.10 vs 0.19). All study groups were less dependent on their pedicle for perfusion than controls. The use of the harmonic scalpel and increased inflammation seem pro-angiogenic, although they do not reduce flap necrosis after simulated pedicle injury. Neovascularisation will preferentially bridge to the skin at the inset rather than tissues in the base of the wound. It is likely that flap necrosis is the result of a combination of unfavourable variables rather than one in isolation.