Different methods of hydroxyapatite-based coatings on external fixator pin with high adhesion approach

In this review paper, different methods of hydroxyapatite-based coatings on external fixation pins with improvement in the adhesion strength are explained. Different coating methods such as dip coating, surface-induced mineralization, plasma spraying, physical vapor deposition magnetron sputtering, micro-arc oxidation, electrophoretic deposition, chemical vapor deposition, ion beam assisted deposition, sol-gel dip coating, pulsed laser deposition, and electrohydrodynamic coating are investigated. The micro-arc oxidation method showed high degradation delaying of the substrate with a high-voltage electrolyte solution. Moreover, controlling the coating porosity by applying the gas is a good feature of the physical vapor deposition magnetron sputtering method. The comparison of the hydroxyapatite (HA) coatings method showed that the plasma spraying method leads to better coating features between the coating methods on the implant pins.