Flexible intramedullary nails for limb lengthening: a comprehensive comparative study of three nails types.

This study aims to investigate the comparative study of calcium phosphate coatings for flexible intramedullary nails (FINs) used to lengthen long tubular bones. The presence of a calcium phosphate coating deposited by micro-arc oxidation or a composite coating based on a copolymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) and hydroxyapatite (HA) on the surface of the FIN significantly enhanced the regeneration of bone in the area of osteotomy during limb lengthening by combined osteosynthesis. The investigation of the physicochemical properties of the FIN coated with calcium phosphate via micro-arc oxidation demonstrated that the improved bone tissue formation resulted from favorable conditions for adhesion, proliferation, and differentiation of multipotent stem cells into osteoblasts on the coating surface. The composite coatings only stimulated the formation of bone tissue in vivo, primarily because of the piezoelectric properties of the VDF-TeFE copolymer.