Magnesium alloys are a promising material for bioresorbable implants in osteosynthesis manufacture. Magnesium is contained in bone and muscle tissue and it participates in various metabolic processes of the human body. Magnesium biocorrosion products have good biocompatibility. Magnesium alloys positively affect the human body, but their properties and quality do not always meet the requirements for using them as implants. It is possible to improve the magnesium alloy's properties by improving the refining processes of the liquid alloy. The aim of our research is to investigate and test different materials for refining magnesium melt. Optical microscopy, standard methods for determining the mechanical properties of magnesium alloy, and special methods for determining the refining ability of various materials were implemented. The structure and properties of the cast magnesium alloy AZ91 in its refined state were investigated. Filtering materials that provide melt refining for obtaining high-quality casting with an increased set of properties are proposed. It has been shown that the usage of a carbon-containing filter provides not only effective refining of the alloy but also its additional modification. At the same time, an increased amount of intermetallic phase is observed in the alloy structure, which improves its structure and physical and mechanical characteristics. The developed complex technology for processing the AZ91 liquid melt allows improvement of the yield of suitable castings for the manufacture of implants and improves their quality. Preclinical testing of implants, which were manufactured using the experimental technology, was carried out and a positive result of their usage was obtained.