Free pectoral skin flap in the rat based on the long thoracic vessels: a new flap model for experimental study and microsurgical training.

Miyamoto et al investigated the vascular anatomy of the rat pectoral region in order to develop a new free pectoral skin flap model. Their study consisted of 2 experiments. Experiment 1 was an anatomical dissection of the rat pectoral region. Experiment 2 was the microsurgical-free transfer of 20 rat pectoral skin flaps to the cervical or groin region: half of the microsurgical anastomoses were end-toend and half were flow-through anastomoses. The authors concluded that the free rat pectoral skin flap is a simple and reliable model that may be used for microvascular experimentation and microsurgery training. In their study, Miyamoto et al found that the axillary artery diameter was larger than the femoral artery in rats, making it a better match for anastomoses to the long thoracic artery during cervical transfer. For this reason, they point out that the free pectoral skin flap more closely resembles a clinical free flap transfer than the superficial epigastric flap model. The authors admit that the chief disadvantage of the pectoral skin flap is the difficulty in dissecting the axillary vessels, because of the surrounding connective tissue. Furthermore, if dissection is careless or ligation of the axillary vessels fails, the operation can be complicated by difficult to control bleeding or air embolism. Although these are significant disadvantages, as in all new techniques, there is bound to be a learning curve. Moving forward, only time will tell how quickly and proficiently trainees can master this new flap. Although many different microsurgical models exist in an assortment of animal models, there is no one animal that has advanced our clinical knowledge as much as the rat. There are over 16 microsurgical models currently used in rats, including the epigastric skin flap, gastrocnemius muscle flap, latissimus dorsi muscle flap, pectoralis muscle flap, fibular bone flap, and omental flap. Having a multitude of microsurgical models plays a key role in training new microsurgeons and improving our knowledge base. For example, advancements in clinical microsurgery have created numerous questions and the corresponding rat models have enabled us to look for new answers without resorting to large animals or sacrificing human safety. Moreover, the availability of molecular reagents for the rat has enabled researchers to study microvascular physiology on the cellular and subcellular levels. The first rat pectoralis major muscle flap was described by Zhang et al in 1994. Zhang’s rat pectoralis major muscle flap, based on the lateral thoracic vessels, was transplanted to both the cervical region and the groin region and was used for delay procedures. After the initial description of the rat pectoralis major muscle flap, researchers used the model to study muscle degeneration and skin changes resulting from ischemia or denervation and balloon expansion for use in sternoplasty. Other pectoralis major musculocutaneous models have subsequently been described. In 1999 Akyurek et al described the first pedicled pectoral skin flap in the rat. In 2005, Ulusal et al described a free pectoral skin flap in the rat based on the axillary vessels. The current study by Miyamoto and colleagues represents the latest advancement in pectoralis flaps in rats, as it is the first free pectoral skin flap based on the long thoracic vessels. Rat free flap model development may be a good prognosticator of the future directions of clinical medicine. For example, prefabricated tissue engineered rat free flaps may be a glimpse into the future of clinical microsurgery. Linking conventional flaps and tissue engineered flaps, Morrison and coworkers have developed an in vivo tissue engineering model in the rat involving a vascularized chamber that may be microsurgically transplanted. Experimental models like this one and others could have marked clinical implications in the treatment of traumatic defects or congenital deficiencies. Finally, with the use of flap models in the rat, our understanding of free flap physiology, biology, and pharmacology will lead the way toward significant advances in clinical microsurgery. Miyamoto and coauthors report that this new pectoralis skin flap is capable of being transplanted to both the groin and cervical regions in an end-to-end or flow-through fashion. We feel that this model shows promise as an alternative model to the superficial epigastric flap. The authors are to be congratReceived November 19, 2007 and accepted for publication, after revision, November 19, 2007. From the Institute of Reconstructive Plastic Surgery, New York University Medical Center, New York, New York. Reprints: Stephen M. Warren, MD, Institute of Reconstructive Plastic Surgery, New York University Medical Center, 560 First Ave, TH-169, New York, NY 10016. E-mail: stephen.warren.md@gmail.com. Copyright © 2008 by Lippincott Williams & Wilkins ISSN: 0148-7043/08/6104-0479 DOI: 10.1097/SAP.0b013e318162b058