Nonlinear Finite Element Simulations to Elucidate the Determinants of Perforator Patency in Propeller Flaps

Abstract

The propeller-type flap design is increasingly used in reconstructive surgery for various regions of the body. To date, determinants of perforator patency when subjected to twisting have not been elucidated. We propose a simulation model to study parameters affecting perforator patency under such conditions. Nonlinear finite element procedure was used to simulate a perforator consisting of an artery and a vein with both ends fixed. A rigid body was attached to the top of the perforator for applying prescribed angular displacement. The effect of the following parameters on the pedicle patency was determined: (1) increasing angle of twist, (2) vessel stiffness, (3) vessel length, (4) diameter, (5) intraluminal pressure, and (6) the presence or absence of blood flow during twisting. Simulation results were reported in effective stress and strain on the twisted pedicle. In the context of perforator patency, effective strain, which is a measure of vessel deformation or collapse, is the more relevant outcome. The vein was more prone to occlusion because of its weaker wall and lower intraluminal pressure. Four factors that affected perforator patency were identified: angle of twist, intraluminal blood pressure, and perforator diameter and length. There was no significant difference whether twisting was performed prior to or after restoration of blood flow (P > 0.05). Therefore, to optimize condition for maintaining perforator patency, the angle of twist should be kept <180 degrees, perioperative blood pressure should be kept stable (avoiding periods of hypotension), and the selected perforator should be approximately 1 mm in diameter and >30 mm in length. We found that the propeller flap is a feasible design. This study defined the determinants of perforator patency and will serve as a useful guide when performing such flaps.

Versatility and “flap efficiency” of pedicled perforator flaps in lower extremity reconstruction

“…Nonlinear finite element simulation calculated that a 1.0 mm diameter and 3.0 cm pedicle length is required to adequately provide 180 arc of rotation in propeller design. 29 Anatomical studies of the PAP flaps support these calculations claiming adequate rotation of vessels 0.8 mm in diameter with 3.7e5.4 mm pedicle length. 3 The PAP flap based on the distal third of the lower leg is our favored choice in traumatic injuries.…”

Clinical Applications of Perforator-Based Propeller Flaps in Upper Limb Soft Tissue Reconstruction

“…Five previous experimental studies have studied the effect of pedicle twisting on flap survival. [22][23][24][25][26] Based on these studies and reports in the literature, perforator-based propeller flaps with a rotation up to 180°have shown to be viable and versatile. 2,3,8,9,21,27 In patients needing 180°of flap rotation, we attempt flap rotation in both a clockwise and counter-clockwise fashion.…”

Intercostal artery perforator propeller flap for reconstruction of trunk defects following sarcoma resection

“…Generally speaking, a 3-cm pedicle length is desirable for a 180 propeller rotation, and will not compromise the flap vascularity. 24 Although the anatomy of the ICAP has been studied by many authors, the detailed description of the perforator distribution of the entire ICA system is still not available. In addition, there is variation of perforator location in the different intercostal spaces.…”