Titanium and its alloys are widely used as orthopedic devices for fixation of bone fractures. A combination of low elastic modulus and suitable implant plate thickness, to adjust the stiffness of the implant plate, can improve the healing process. The present study investigates the effect of titanium plate stiffness on the bone formation during the early stage of healing in rabbit femurs. Materials with different elastic moduli, Ti-29Nb-13Ta-4.6Zr (TNTZ) and Ti-6Al-4V ELI (Ti-64), were used as implant plates, and the effect of plate thickness on the bone healing ability was explored. Two types of titanium implant plates of thickness 0.5 mm were used, and after three weeks, the femurs were harvested. Bone cross-sections of the femur were analyzed using scanning electron microscopy, hematoxylin & eosin staining, and Vickers hardness test. Fixations using both the implant plates showed almost similar bone structures but different average total callus areas. Fixation using the TNTZ implant plate resulted in a larger area of callus formation than that using the Ti-64 implant plate of same thickness, but the callus hardness was almost similar. Therefore, we conclude that an overly flexible fixation system results in an excessive callus formation and delayed union. Suitable implant characteristics can result in enhanced bone healing, superior bone properties, such as improved hardness.
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