Magnetic transcutaneous fixation: an experimental study in pigs

Background: Magnetic subdermal implants have never been studied in the context of magnetic fixation 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 necrosis.

Objective: To evaluate the feasibility of transcutaneous magnetic fixation and assess secondary skin changes when subjected to a continuous static magnetic field.

Methods: Using the pig as an animal model, 72 implants were introduced in 12 animals. After wound healing, ultrasonography was performed to measure implant depths. Computer simulations were applied to allow magnetic attachment between implants and external devices without impairing local blood flow. External devices of different magnetic strengths were applied over the skin for 7 days. Local skin was examined and collected for analysis. A senior dermatopathologist blindly examined skin specimens and controls for abnormal findings, measuring dermal and epidermal thickness. Statistical analysis (P <0.05) was performed over the data.

Results: Nineteen implants presented extrusion. The remaining 53 skin sites underwent magnetic compression, of which 43 (81%) evolved uneventfully. Implant depth varied between 4.6 mm and 8.3 mm (5.8 mm; ± 8.6 mm) with estimated pressure levels between 13.28 mmHg and 37.04 mmHg (27.6 mmHg; ±6.0 mmHg). Stronger magnets were associated with an increase in dermal thickness (P = 0.011) and neovascularization (P = 0.045).

Conclusions: Transcutaneous magnetic fixation is compatible with skin viability in vivo, under experimental conditions. Skin interposition between two permanent magnets resulted in a continuous static magnetic field stimulation, which showed similar effects to pulsed electromagnetic fields reported on scientific literature.