Provided herein are bone anchor devices including embodiments using adaptive materials, including shape memory materials such as shape memory alloys. Embodiments using shape memory alloys may use super-elastic properties of shape memory alloys to provide forces and deflections that actuate bone anchoring element(s) within bones. Embodiments of bone anchoring elements may be created that actuate with respect to one or more pivot point(s), with the bone anchoring elements on an opposite side of the pivot point from the actuating member composed of, for example, shape memory material. The pivot point(s) of a bone anchor device may be positioned in a central portion of the bone anchor device. The central portion of the bone anchor device may span between two pieces of bone or two separate bones (e.g., two bones of a joint) into which bone anchoring elements may be embedded and fixed.
