Mechanical behavior of a NiTi superelastic bone plate obtained by investment casting assisted by additive manufacturing

Abstract

The mechanical behavior of nickel-titanium shape memory alloys (NiTi SMA) presents unique features that benefit the bone fracture healing process: matching elastic modulus ranges, the ability to recover large deformations, and mechanical dissipation capacity. In this sense, this work proposes a new manufacturing process for NiTi SMA bone implants, particularly bone plates: additive manufacturing assisted investment casting (IC). This process delivers near-net NiTi SMA parts with either simple or complex shapes, also allowing a high degree of customization. Four identical NiTi SMA bone plates were manufactured through IC and characterized. Four-point bending tests were performed on the bone plate prototypes to verify their mechanical and fatigue behaviors. The NiTi bone plates have an elastic modulus of the order of 49 GPa at 37 °C and recovered all deformations upon unloading when submitted to four-point bending deflections up to 4 mm. The fatigue life was between 103 and >105, depending on the deflection amplitude. Our next work with this technology will address aspects of cytotoxicity and implantation of the part in animals.

Design of an orthopedic smart splint using nickel-titanium shape memory alloy

“…Shape memory alloys (SMAs) are defined as a group of materials that can reach a predetermined shape or size once subjected to an appropriate thermal procedure throughout the production process of the designed material [19]. This has been proven by many previous literary studies that studied the properties of shape memory alloys [7], [20]. The idea of designing an intelligent splint with different features has recently attracted many researchers because of its importance in developing methods and reducing the treatment period for patients with various fractures [21]- [25].…”