Intramedullary medical devices (e.g., intramedullary nails) and methods for their use and manufacture are described herein. The intramedullary medical devices described herein may provide sustained compressive forces across a bone fusion site despite bone resorption processes. Through various embodiments, the intramedullary medical devices described herein may provide non-linear force curves relative to displacement. Intramedullary medical devices are described with multiple elements made of different materials. Examples of intramedullary medical devices are described with shape memory alloys.
