Keystone Flaps

Abstract

The keystone perforator flap (KPF) was first introduced in 2003 by Behan et al for use in reconstruction after skin cancer excision. Since its initial description, KPF use has been expanded to complex defects of various etiologies and disorders throughout the body. At its most basic, the KPF is a perforator-type flap designed with a 1:1 flap-to-defect width ratio. Keystone perforator flaps are specifically raised on pedicles arising from musculocutaneous or fasciocutaneous perforator vessels. Major advantages of the KPF derive from the maintenance of perforator vascular territories, perforosomes, permitting increased flap viability. In turn, this allows for more aggressive undermining in sites away from perforators when greater skin mobilization is necessary. Furthermore, the KPF is relatively easy to perform leading to shorter operative times and no postoperative monitoring period. There are basically 4 different types of keystone flaps in order of increasing undermining and disturbance of underlying fascia. These different classifications of KPFs may be used in different anatomical locations over the entire body based on skin laxity and defect size/depth. Numerous advancements and modifications have been documented adapting the KPF to specific conditions, including myelomeningoceles, and scrotal and lower eyelid defects. The purpose of this article is to provide an organized review of the KPF with emphasis on different classifications, applications, and limitations as well as an overview of the surgical technique. We have additionally included a discussion on KPF physiology and review of current literature.

Keystone design perforator island flaps for coverage of non-oncological periarticular defects surrounded by the zone of injury

“…KDPIF reconstruction has expanded from simple to complex defects throughout the body because of its evident advantages, including its simple defect-adaptive design, easy reproducibility, high level of safety, and short procedural time. [2][3][4][6][7][8][9] Relative contraindications for KDPIF reconstruction include traumatic, irradiated, and inflammatory defects. 3,9 These defects differ from oncological defects in that the surrounding tissues have a tendency to be under the zone of injury and are usually accompanied by wound infection.…”

“…Among various local flaps, the keystone design perforator island flap (KDPIF) devised by Behan 6 in 2003 has been applied to various fields of reconstructive surgery in the past decade because of its design simplicity, robust vascular supply, and easy reproducibility. 3,[7][8][9] The KDPIF, similar to the perforator-based island flap first described by Kim et al 10 in 2010, does not require microsurgical perforator dissection, allowing for a safe and rapid operation. 2,3,6,7 In numerous studies of KDPIF reconstruction, the causes of defects were usually oncological (after skin and soft tissue tumor removal), 3 and few reports have described periarticular defect coverage.…”

Evolution of local perforator flaps in lower extremity reconstruction

“…The flap is designed so that each limb of the flap is 90 degrees from the longitudinal axis of the flap. This has been described throughout the literature for lower extremity defects mostly in the setting of oncologic reconstruction [26][27][28] with good outcomes. Limitations of the keystone flaps include limited advancement and no rotational movement.…”

A comparative study for tension-reducing effect of Type I and Type II keystone perforator island flap in the human back

“…Fundamentally, the KPIF is an island-shaped advancement flap based on the presence of random multi-perforators arising from fasciocutaneous or musculocutaneous perforators, which are often called central hot spots of perforators 1 – 9 . Thus, the center of the KPIF should be located near these hot spots, and the orientation of its longitudinal axis should correspond with the long axis of the defect to maximally capture the dominant perforators with linking vessels, thereby securing stable and reliable flap perfusion 3 , 7 . Behan considered that the vascularity of the KPIF was suprafascial, and intraracial network circulation from the perforator axis was randomly located; however, it must be located within the dermatomal precincts because the blood supply must run along with a nerve supply 1 , 5 .…”

“…In addition to these vascular support basics, KPIF has a unique biomechanical property − the recruitment of tissue laxity 3 , 8 , 10 . As the keystone in Roman arches locks other stones in place, the KPIF locks into the defect through the fusion of two opposing V–Y flaps 1 , 3 , 7 . Behan’s original concept of the KPIF flap is that either end of the V–Y advancement flap facilitates the recruitment of surrounding tissues and the redistribution of skin tension perpendicular to the direction of flap advancement, which confers a tension-reducing effect on the KPIF 3 , 8 – 10 .…”