The keystone design perforator island flap. Part I: anatomic study.

Background: The keystone design perforator island flap has been described as a curvilinear shaped trapezoidal design flap that is essentially two V-Y flaps end-to-side. Viability of the flap is thought to be supported by the subcutaneous vascular network and fascial and muscular perforators. The aim of this study was to assess the vascularisation of this flap and the behaviour of the skin paddle when submitted to important traction forces.

Methods: Fourteen flaps were raised after a skin defect was created on various regions of two fresh cadavers. Longitudinal and transversal cutaneous markings allowed analysis of the behaviour of the skin paddle during the course of direct closure and flap mobilisation. Injections of coloured solutions were performed before and after the flap elevation to visualise the vascularisation of the flap.

Discussion: The superficial vascular network was always preserved by the blunt dissection of the flap's margins and perforators arising from the underlying muscular tissue were constantly found. The dual vascularisation of the flap was then confirmed. Cutaneous markings showed the skin paddle to remain static in size with advancement of the surrounding tissues to meet the flap. The flap advancement opens a long and narrow defect on the lateral margin, the approximation of which in a V-Y fashion reduces even more the surface to be closed. Elevation of the flap also allows distribution of the tension forces over a greater surface both within the flap as well as the surrounding tissues.

Conclusion: The vascular reliability of this flap and its versatile design potentially gives it a universal application all over the body.