Manufacturing of monolithic superelastic rods with variable properties for spinal correction: Feasibility study

A new concept of monolithic spinal rod with variable flexural stiffness is proposed to reduce the risk of adjacent segment degeneration and fracture associated with rigid spinal fixation techniques while providing adequate stability to the spine. The concept is based on the use of Ti–Ni shape memory alloy rods subjected to different processing schedules implying local annealing, cold work, or a combination of both. A feasibility study of the concurrent technological routes is performed by comparing their potential to locally control material microstructure and properties. [Display omitted] •Rigid spinal instrumentations are associated with adjacent segment degeneration.•Rod with variable flexural stiffness could improve the instrumentation.•Mechanical properties of Ti–Ni shape memory alloys are influenced by the processing.•Ti–Ni rod with variable flexural stiffness can be produced by local processing.