Mechanically Stable Intraspinal Microstimulation Implants for Human Translation
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The goal of this study was to develop stable intraspinal microstimulation (ISMS) implants for use in humans to restore standing and walking after spinal cord injury. ISMS electrically activates locomotor networks within the lumbar region of the spinal cord. In animals, ISMS produced better functional outcomes than those obtained by other interventions, and recent efforts have focused on translating this approach to humans. This study used domestic pigs to: (1) quantify the movements and length changes of the implant region of the spinal cord during spine flexion and extension movements; and (2) measure the forces leading to the dislodgement of the ISMS electrodes. The displacement of the spinal cord implant region was 5.66 ± 0.57 mm relative to the implant fixation point on the spine. The overall length change of the spinal cord implant region was 5.64 ± 0.59 mm. The electrode dislodgment forces were 60.9 ± 35.5 mN. Based on these results, six different coil types were fabricated and their strain relief capacity assessed. When interposed between the electrodes and the stimulator, five coil types successfully prevented the dislodgement of the electrodes. The results of this study will guide the design of mechanically stable ISMS implants for ultimate human use.
KeywordsIntraspinal implant Dislodgment forces Lumbar spine biomechanics Strain relief Coiled lead wire
Functional electrical stimulation
Foreign body response
Spinal cord injury
The authors thank Mr. Robert Butz for assistance with early measurement of electrode dislodgement forces, and Mr. Theodore Ng and Dr. Anastasia Elias for assistance in preparing surrogate spinal cords. Funding for this work was provided by the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada and Alberta Innovates – Health Solutions (AIHS). AT was supported by a Vanier Canada Graduate Scholarship and an AIHS Graduate Studentship. VKM was an Alberta Heritage Foundation for Medical Research Senior Scholar.
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