Primary Design of a Shape Memory Alloy Expandable Insert to Enhance Pedicle Screw Performance

Shape Memory Alloys, such as Nickel Titanium, undergo a phase transformation in their crystalline structure when transformed from Austenite into Martensite. This inherent phase transformation is the basis for the unique properties of shape memory and superelasticity. Shape memory is attributed to the recovery of large mechanically induced deformations upon raising the temperature upto a specific level (Af). The superelasticity is the ability of the material, at a temperature above Austenite start Af, to recover mechanical deformations upon unloading. Thanks to superelasticity, shape memory effect, high damping capacity, corrosion resistance and biocompatibility, NiTi SMA alloys gain researchers attention for implementation in biomedical fields for the past 40 years [1].