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

Area of Science:

• Biomaterials Engineering
• Spinal Surgery
• Materials Science

Background:

• Rigid spinal fixation techniques can lead to adjacent segment degeneration and fracture.
• There is a need for spinal implants that offer adequate stability while mitigating risks of adjacent segment pathology.

Purpose of the Study:

• To propose a new concept of a monolithic spinal rod with variable flexural stiffness.
• To investigate the use of Ti-Ni shape memory alloy rods for this purpose.
• To assess the feasibility of different processing schedules for controlling material properties.

Main Methods:

• Concept development of a monolithic spinal rod.
• Utilizing Ti-Ni shape memory alloys.
• Applying various processing schedules: local annealing, cold work, and combined methods.
• Feasibility study comparing technological routes for microstructure and property control.

Main Results:

• Demonstrated the potential for locally controlling the microstructure and properties of Ti-Ni shape memory alloy rods.
• Established feasibility of using different processing schedules to achieve variable flexural stiffness.
• Provided a basis for developing spinal rods that can adapt their stiffness.

Conclusions:

• The proposed concept of a variable flexural stiffness spinal rod using Ti-Ni shape memory alloys is feasible.
• This approach offers a promising strategy to reduce adjacent segment degeneration and fracture.
• Further development could lead to improved spinal fixation devices with enhanced patient outcomes.