The Experimental Study On Relationship Between Adhesive Strength Of Hydroxyapatite (HA) Coating And Biomechanics Behavior Of HA-coated Prosthesis

The technology of Bone and joint developed rapidly along with the extending of average life expectancy, the aggravating trend of aging population , increasing of bone and joint diseases, especially the degenerative joint disease, and the increase of medical service requirements. There has been a significant development of artificial joint replacement technology in the field of biomechanics, the surgical manner, prosthesis design and material in recent years. We investigated on the adhesive strength and biomechanics behaviour of the HA-coated prosthesis by histopathological examination, detection of coating adhesive strength and biomechanics, using Ti-coated prosthesis as Control. The adhesive strength is an important factor affecting the stability of HA-coated prosthesis in vivo and its service life. Statistical data from histopathological examination and bone histomorphometry showed that the bone formation around HA-coated prosthesis was significantly higher than that around the Ti-coated prosthesis (P<0.01) at the early stage of prosthesis implantation, while the ultimate shear strength of HA-coated prosthesis was much lower than that of Ti-coated implant (P<0.01). The histopathological observation after the push-out test of the prosthesis showed that there were accumulations of crumby or strip-like eyewinker particles on the surface of bones that newly grew around the HA-coated prosthesis. Surface Energy-dispersive X-ray spectroscopy (EDX) analysis also confirmed that the shear stress induced the decohesion of HA from the substrate of the prosthesis. Further study showed that the adhesive strength of HA coating was significantly lower than that of Ti coating (P<0.01). This study showed that although the HA coating has satisfactory effect on the early bone formation and the prosthetic stability, such stability is on the basis of the coating adhesive strength and the stability of the interface. Due to the deficiency of HA-coating in adhesive strength, the early stability of prosthesis may be gradually destructed by the combined effects of the shear loads of human body, the coating degradation, and other factors.