1. 2022;25;E375-E383Shape Memory Nitinol Based Minimally Invasive Spinal Cord Stimulation Device Concept for Improved Pain Management
   Experimental Study
   Vikas Srivastava, PhD, Andrea Lu, BSc, Ruth Sullivan, ., Albert E Telfeian, MD, PhD, and Shailen G. Sampath, MSc.

BACKGROUND: Spinal cord stimulation (SCS) is a common treatment for neuropathic pain. There are 2 main categories of SCS leads: paddle leads and cylindrical leads. Paddle leads have reduced long-term complications and provide better coverage of target dermatomes when compared to cylindrical leads. However, insertion of a paddle lead requires invasive surgery that comes with significantly higher costs and more short-term complications, such as postoperative pain and infection. In contrast, cylindrical leads can be inserted minimally invasively using percutaneous techniques but provide less coverage of targeted dermatomes and have a higher tendency to migrate from intended neuronal targets.

OBJECTIVES: Our objective is to develop a novel improved cylindrical spinal cord stimulation device that can convert into an optimal geometry once exposed to the body’s environment after minimally invasive surgery. Such a device would be able to reduce long-term complications, lead migration, and better cover targeted dermatomes.

STUDY DESIGN: Biomaterial selection, medical intervention device design with an in-vitro lab-scale test, and cadaveric experimental study.

METHODS: A shape memory alloy nitinol-based cylindrical lead was designed, and its nitinol core material was processed and geometrically programmed for percutaneous insertion into the epidural space and morphing into an optimal geometry once exposed to the body’s environment. Deployment of the nitinol component of the design was tested in the lab and human cadaveric models of the epidural space.

RESULTS: Deployment of the nitinol component of the proposed cylindrical lead was successfully demonstrated in both a lab model of the epidural space and in the epidural space of a human cadaver in a minimally invasive fashion, indicating that a similar component could be used clinically in a full SCS electrode manufactured in a custom final geometry.

LIMITATIONS: The focus of this study was to test the deployment of a novel minimally invasive lead that provides optimal coverage of intended dermatomes using in-vitro methods. Our study does not include in vivo trials. We do not test the electrical components of the design proposed since our design does not make changes to the electrical components of current commercially used cylindrical leads.

CONCLUSION: The unique shape memory property of nitinol shows promise in allowing cylindrical spinal cord stimulation leads to expand into a more optimal geometry within the epidural space. By having a body temperature-dependent geometry change, nitinol-based cylindrical leads could reduce lead migration, increase dermatomal coverage, and increase electrode density while maintaining the advantages of minimally invasive insertion.

KEY WORDS: Spinal cord stimulation, pain management, shape memory alloy, nitinol, minimally invasive surgery, percutaneous insertion