Osteoinductive composite coatings for flexible intramedullary nails

•VDF-TeFE copolymer/HA composite coatings for flexible intramedullary nail were designed.•The influence of the amount of VDF-TeFE on properties of composites was studied.•VDF-TeFE has electrical activity phases regardless of its content in the composite.•Osteoinductive properties, likely is caused by piezoelectric properties of the composite.

This work presents composite coatings based on a copolymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) and hydroxyapatite (HA) for flexible intramedullary nails (FIN). The effect of the proportion of VDF-TeFE (100-25% wt.) on physicochemical and biological properties of the composite coatings was investigated. It was shown that a decrease of VDF-TeFE in the coating hinders its crystallization in β and γ forms which have piezoelectric properties. The decrease also reduces an adhesive strength to 9.9 ± 2.4 MPa and a relative elongation to 5.9 ± 1.2%, but results in increased osteogenesis. It was demonstrated that the composite coatings with 35% VDF-TeFE has the required combination of physicochemical properties and osteogenic activity. Comparative studies of composite coatings (35% VDF-TeFE) and calcium phosphate coatings produced using micro-arc oxidation, demonstrated comparable results for strength of bonding of these FINs with trabecular bones (~ 530 MPa). It was hypothesized that the high osteoinductive properties of the composite coatings are due to their piezoelectric properties.

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