Analysis of Corrosion Behavior of Brushite-Coated Magnesium in Different Environments: Non-Hematoma vs. Hematoma.

Abstract

The corrosion rate of these alloys is observed to be the fastest immediately after implantation. In addition, bleeding can accelerate corrosion and cause treatment failure in vivo, and therefore, it is necessary to optimize the corrosion rate. The brushite (CaHPO₄・2H₂O) coating treatment, a type of calcium phosphate, is used as a method to optimize the corrosion rate of magnesium and is expected to have the same coating effect under hematoma as under non-hematoma conditions. The purpose of this study was to evaluate the effect of brushite coating treatment with and without hematoma up to 14 days of implantation in vivo experiments. Specimens of cylindrical Pure Magnesium (99.9%, 1.2 mm × 6 mm), treated with a brushite coating by precipitation, were implanted in hematoma or non-hematoma rat femurs. The insoluble salts that precipitated on the specimens were analyzed by inductively coupled plasma mass spectrometry, scanning electron microscopy-energy dispersive X-ray analysis, and Raman spectroscopy. Results showed that weight loss at 14 days of implantation in the hematoma group (24.83 ± 2.26 μg mm^-2) was significantly greater than in the non-hematoma group (18.88 ± 1.95 μg mm^-2). The hematoma group had increased precipitation of insoluble salt magnesium and phosphorus. However, the amount of magnesium contained in insoluble salt per weight loss was significantly greater in the non-hematoma group at all time points, particularly after 1 days of implantation (non-hematoma group: 19.42% ± 3.56%; hematoma group: 10.73% ± 0.41%, p < 0.01). The brushite coating transformed the insoluble salts in the surface layer to an optimum structure compatible with the implantation environment. This enhanced the coating's protective function and more effectively inhibited magnesium corrosion. Given the clinical challenge of fully controlling intra-and postoperative bleeding, a brushite coating adaptable to hematoma conditions offers significant utility.