Bioactive Surface Modifications on Bioresorbable Bone Screws: A Step Forward in Orthopedic Surgery

Despite metals currently being widely used in orthopedic surgery, their mechanical properties significantly differ from the surrounding tissues and organs, causing low biocompatibility. Biodegradable, non-toxic, and non-immunogenic materials seem to be more convenient for clinical implementation. Our research was aimed at the construction of a polylactide screw covered with collagen, nanohydroxyapatite, and polylactide, with a variant including silver nanowires for antibacterial properties, as well as the analysis of their physico-chemical and biological properties. Adherent human osteosarcoma cells (2T line) were shown to grow on the porous surface layers. A cytotoxicity assay using WST1 revealed the non-toxic nature of the coatings and showed an increase in cell adhesion and proliferation. Safety and efficacy were also evaluated in vivo with the coated screws implanted into the metatarsal bones of minipigs. Histological analysis at 29 and 58 days post-screw-implantation revealed that the coated samples accelerated bone tissue regeneration compared to uncoated controls. This was evidenced by a higher bone-to-granulation tissue ratio, reduced inflammatory cell counts, and increased osteoblast/osteoclast activity at the early stage during the initial days after implantation. The results confirm that the developed bioactive coatings enhance biocompatibility and osteointegration.