Fixação magnética transcutânea: estudo experimental em suínos

Abstract

Magnetic subdermal implants have never been studied in the context of magnetic attachment of an external device to the body´s surface. Excessive attractive force between the implant and the external device may compromise local circulation due to mechanical compression, leading to ischemia and tissue necrosis. The objective of this study was to evaluate the feasibility of Transcutaneous Magnetic Fixation (TMF) and also to study the secondary alterations of the skin when submitted to a continuous static magnetic field. The method employed two experiments with pigs. In the first, 30 subcutaneous magnetic implants (n = 30) were introduced into two pigs. After wound healing, external magnets were applied to the skin with varying magnetic forces, generating compression. The cutaneous circulation of the skin under compression was evaluated using the Laser Speckle Contrast Imaging technique. The depth of the implants was measured by ultrasonography and computational simulations were applied to the calculation of the different pressure values, considering the different distances between the magnetic pieces. In the second experiment, 72 implants were implanted in 12 pigs. After wound healing, ultrasound was performed to measure the depth of the implants. Computational simulations were applied to allow magnetic fixation between the implants and external devices without damaging the local blood flow. External devices of different magnetic forces were applied over the skin for seven days. The local skin was examined and collected for histopathological analysis. A senior dermatopathologist examined skin specimens and controls in a blinded manner for abnormal findings, also measuring dermal and epidermal thickness. A statistical analysis was performed over the data collected (p <0.05). As result of the first experiment, two linear regression models showed an inverse correlation between pressure exerted and cutaneous perfusion (p = 0.0036 and 0.0004), with significant variation mainly in the initial increases of pressure up to 20 mmHg. In the second experiment, stronger magnets were associated with an increase in dermal thickness (p = 0.011) and neovascularization (p = 0.045). In conclusion, TMF showed to be compatible skin viability of the skin in vivo under experimental conditions. The interposition of living skin between two permanent magnets resulted in a continuous stimulation by the static magnetic field, whose effects were similar to the pulsed electromagnetic fields reported in the scientific literature.