Mechanically Stable Intraspinal Microstimulation Implants for Human Translation

Abstract

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.

The Role of Functional Neuroanatomy of the Lumbar Spinal Cord in Effect of Epidural Stimulation

“…Particularly, the swine spine has gained attention as a suitable model due to its similarity to humans in terms of vertebral morphometry (McLain et al, 2002 ; Busscher et al, 2010 ; Sheng et al, 2016 ) and biomechanical properties (Yingling et al, 1999 ; Sheng et al, 2010 ); however, a description of the swine spinal cord anatomy and its intersegmental relationship with the spine is missing. In this study we chose the swine model due to its translational relevance (Bozkus et al, 2005 ; Zurita et al, 2012 ; Hachmann et al, 2013 ; Lee et al, 2013 ; Guiho et al, 2017 ; Toossi et al, 2017 ) and its emergence as an optimal model to study EES following SCI (Schomberg et al, 2017 ).…”

Comparative Neuroanatomy of the Lumbosacral Spinal Cord of the Rat, Cat, Pig, Monkey, and Human

“…As an example, intraspinal microstimulation (ISMS) [17], [18], [33] is a spinal cord neuroprosthesis for restoring mobility after spinal cord injury that involves the implantation of fine microelectrodes into the ventral horns of the spinal cord to activate functional spinal motor networks. ISMS microelectrodes are typically implanted perpendicularly to the major axis of the cord along the anteroposterior (dorsoventral) axis [22], [42], and target regions within Rexed lamina IX of the spinal cord [35], [46], [47].…”

Spinal Interfaces: Overview

“…By braiding extremely fine wires, a very high overall compliance electrode and cabling technology is produced that can be inserted within the spinal cord with the help of a removable cannula guide and produce minimal histological damage to the central nervous tissue after long-term implantation (Kim et al 2013a). As part of recent translation efforts, Mushahwar and colleagues have also begun development of ISMS implants for humans, performing initial mechanical testing of the implants in porcine models (Toossi et al 2017). Wireless stimulators may also offer freedom from the cable tethering problem and potentially dura resealing.…”