Modern polymer composite materials for bone surgery: Problems and prospects

Objectives. To discuss the main problems and prospects of creating modern osteoplastic materials based on polymer compositions used for bone surgery.

Methods. This review summarizes the research works devoted to the creation of materials used for bone implants and issues involved in their practical testing, as well as analyzes and synthesizes data of scientific articles on the following topics: rationale for the use of biodegradable materials in bone surgery; biodegradation and bioreparation bone graft processes; requirements for degradable polymer composite materials (PCMs) for biomedical applications; overview of polymeric materials suitable for use in implant practice; impact of modifications of the PCM on the structure and biological activity of the material in biological media; effect of exhaust and heat treatment on the molecular structure of polyalkanoates.

Results. The most promising biodegradable resorbable materials for reparative bone surgery to date are compared. The requirements for these types of materials are formulated and a rationale for their use is provided that takes into account the advantages over traditional metal and ceramic implants. The features of the kinetics and mechanism of biodegradation of implants in their interaction with the bone biological environment of the body from the moment of implant insertion to complete wound healing are considered. As a result of the analysis, factors that may affect the activity of implant decomposition and methods of adjusting the decomposition rate and mechanical characteristics of the material, such as chemical functionalization, the creation of block copolymers, the inclusion of fibers and mineral fillers in the composite, as well as heat treatment and extraction of the composite at the manufacturing stage, were identified. Among the main factors, the influence of the structure of the composite material on its biological activity during interaction with biological media was evaluated. Of polymer materials, the main attention is paid to the most common biodegradable polymers widely used in medicine: polyhydroxybutyrate (PHB) of microbiological origin, polylactide (PLA) and other polymers based on polylactic acid, polycaprolactone (PCL). The effect of their modification by such additives as hydroxyapatite (HAP), chitin and chitosan, and beta-tricalcium phosphate (β-TCF) is considered. Materials based on PHB are concluded as the most promising due to their complete biodegradability to non-toxic products (carbon dioxide and water) and good biocompatibility. Nevertheless, existing compositions based on PHB are not without disadvantages, which include fragility, low elasticity, unstable behavior under high-temperature exposure during processing, implant molding, sterilization, etc., which requires improvement both in terms of polymer modification and in terms of composition of compositions.

Conclusions. The review considers approaches to achieving the properties of materials required for perfect implants. The main requirements for implants are optimization of the time of resorption of the osteoplastic matrix, facilitating the resorption of the osteoplastic matrix synchronized in time with the process of bone regeneration. To achieve these requirements, it is necessary to apply technologies that include modification of polymer composite materials by affecting the chemical composition and structure; introduction of fillers; use of chemical functionalization, orientation extraction, heat treatment. The success of using bone materials based on biodegradable polymers is based on an accurate understanding of the mechanism of action of various components of the implant composition and strict compliance with the tightening regulatory requirements of implantation technology.