Perforator chimerism for the reconstruction of complex defects: A new chimeric free flap classification system

Summary

Complex defects present structural and functional challenges to reconstructive surgeons. When compared to multiple free flaps or staged reconstruction, the use of chimeric flaps to reconstruct such defects have many advantages such as reduced number of operative procedures and donor site morbidity as well as preservation of recipient vessels. With increased popularity of perforator flaps, chimeric flaps' harvest and design has benefited from ‘perforator concept’ towards more versatile and better reconstruction solutions. This article discusses perforator based chimeric flaps and presents a practice based classification system that incorporates the perforator flap concept into “Perforator Chimerism”. The authors analyzed a variety of chimeric patterns used in 31 consecutive cases to present illustrative case series and their new classification system. Accordingly, chimeric flaps are classified into four types. Type I: Classical Chimerism, Type II: Anastomotic Chimerism, Type III: Perforator Chimerism and Type IV Mixed Chimerism. Types I on specific source vessel anatomy whilst Type II requires microvascular anastomosis to create the chimeric reconstructive solution. Type III chimeric flaps utilizes the perforator concept to raise two components of tissues without microvascular anastomosis between them. Type IV chimeric flaps are mixed type flaps comprising any combination of Types I to III. Incorporation of the perforator concept in planning and designing chimeric flaps has allowed safe, effective and aesthetically superior reconstruction of complex defects. The new classification system aids reconstructive surgeons and trainees to understand chimeric flaps design, facilitating effective incorporation of this important reconstructive technique into the armamentarium of the reconstruction toolbox.

Introduction

Modern microsurgical advances have led to the development of elaborate solutions for the reconstruction of complex composite tissue defects. The double-paddled flap, stacked flaps and double flaps with vascular flow-through linkage are examples of such solutions.1, 2 Nevertheless, such complex reconstruction comes at a costly price such as increased donor site morbidity or prolonged operative time.³ Chimeric flaps present a superior alternative to multiple free flaps as the surgeon includes several components in one flap at a price of one donor site. This has the advantages of decreased morbidity, reduced operative time, a greater freedom of inset and improved aesthetic results.1, 4, 5

As in the Greek mythological creature from which the word ‘chimera’ originates; head of a lion, tail of a snake and body of a goat, chimeric flaps are designed to include multiple tissue components. In ‘Classical Chimerism’ flaps are raised as “two components based on an individual named branch that originates from one or same source vessel”.6, 7, 8, 9 Chimeric flaps could also be constructed by microvascular anastomosis of two free flaps, ’Anastomotic Chimerism’. Following the discovery and popularization of perforator flaps concept, these two conventional chimeric patterns have evolved to provide benefits of both perforator and chimeric flaps in a concept we term ‘Perforator Chimerism’. These perforator based chimeric flaps are raised on perforators rather than main arterial branches allowing more selective tissue components (adipose, adipofascial, muscular etc.), single donor site morbidity, greater freedom of inset and arguably better contouring and improved aesthetic result.10, 11 We review our experience of chimeric flaps and propose a simple classification system that would aid both reconstructive surgeons and trainees to design and plan chimeric flaps for the reconstruction of three-dimensional complex and composite defects.