Experimental investigation of tension-reducing effectiveness of keystone perforator island flap.

Background and aim: Nowadays, the reconstruction of large and complex defects with keystone perforator island flaps (KPIF) has gained popularity in plastic and reconstructive surgery. The keystone perforator island flap was described as a curvilinear shaped trapezoidal design flap, with two V-Y advancement flaps end-to-side. It is a multiperforator advancement flap, based on multiple fasciocutaneous or musculocutaneous perforators, described by Behan in 2003. These flaps have a simple harvest technique, an easy-to-implement design, and they are time and cost-saving. Their blood supply lends a versatile and robust character, with less complications. Nonetheless, their biomechanical properties and effectiveness are unclear, the wound-closure tension-reducing effect is not well documented in existing literature. The present study aims to investigate the wound closure tension-reducing effect of type I, type IIA, type Sidney Melanoma Unit I (SMU) and type SMU II KPIFs. The main purpose of this study was to clarify the tension-reducing effect of the KPIF technique, which can contribute to the understanding of the biomechanical benefits of the KPIF.

Methods: This is an experimental, in vivo study, based on twelve white race porcine models (PIC-FII-377), as their anatomy and wound healing process is very similar to that of humans. In this study, 42 wounds that could not be closed by primary wound closure, known as 'unclosable' elliptical defects, were created in six different anatomical regions. The criteria used for not achieving primary wound closure were the breaking of 0 nylon suture or the edges of the wound. Each defect was closed with different types of keystone perforator island flap: type I, type IIA, type Sydney Melanoma Unit I and type Sydney Melanoma Unit II. Keystone perforator island flaps were used in 42 cases. Intraoperative tissue tension was measured by an AXIS FB50, 50 N force gauge tensiometer. In all cases a wide elliptical excision was performed for the primary defect. Before reconstruction, tissue tension was measured across the widest point of the elliptical primary defect. Skin incision was performed for the first flap, without division of deep fascia. After preparing first flap, tension was measured at the widest point of the wound. Furthermore, deep fascia for the second flap was divided, tissue tension across the widest point of the primary defect was measured. Finally, tension was measurement across the widest point of the donor-site after closure of the defect-side flap and V-Y closure of either end of keystone perforator island flap.

Results: In this study were included 12 porcine model (PIC-FII-377). A number of 42 keystone perforator island flaps were performed in this study, in six different anatomical regions, ranging between 3.3 x 12 cm and 16 x 30 cm. All elliptical defects were unclosable, with varying sizes ranging between 2 x 4 cm and 8 x 20 cm. The mean tension that was required to close all wounds with primary closure initially was 24.51 N 10.73 N. After using a type I KPIF a tension decrease of -7.04 N ± 4.93 N was seen, in the case of type IIA KPIF the tension decreased to -12.43 N± 5.63 N. Furthermore, after reconstruction with type SMU I KPIF the tension decreased to -7.38N ± 5.21N. After using a type SMU II KPIF a tension decrease of -10.52 N± 5.74 N was seen.

Conclusions: The main purpose of this study was to clarify the tension-reducing effect of the KPIF technique, which can contribute to the understanding of the biomechanical benefits of the KPIF. The outcomes of the present study suggest that type I, type IIA, type SMU I, and SMU II of keystone perforator island flaps have a significant tension-reducing effects, especially the technique that involves the division of the deep fascia. The results of this experimental research thoroughly explain the benefits of these flaps. The effectiveness of the flap and doubts on biomechanical properties have not been answered so far. It will encourage more plastic surgeons to use the flap, especially given its proven benefits.