Pulsatile spinal cord surrogate for intradural neuromodulation studies

Abstract

We have designed, built and tested a novel spinal cord surrogate that mimics the low-amplitude cardiac-driven pulsations of the human spinal cord, for use in developing intradural implants to be used in a novel form of neuromodulation for the treatment of intractable pain and motor system dysfunction. The silicone surrogate has an oval cross section, 10 mm major axis × 6 mm minor axis, and incorporates a 3 mm diameter × 3 cm long angioplasty balloon that serves as the pulsation actuator. When pneumatically driven at 1 Hz and 1.5 atmospheres (≈ 1140 mm Hg), the surrogate's diametric pulsation is ≈ 100 μm, which corresponds well to in vivo observations. The applications for this surrogate are presented and discussed.

Dynamic loading characteristics of an intradural spinal cord stimulator

“…The HSCMS membrane was then placed in contact with the dorsal surface of a silicone model of the spinal cord, specially designed to have biomechanical characteristics that mimic those of the actual tissues. 11,12 It matched the general shape of the mid-thoracic spinal cord in humans. 13 Because the forces to be measured would be very small, we incorporated a second sensor in order to provide independent verification of the results and to help uncover any systematic uncertainties.…”

Spinal canal surrogate for testing intradural implants

“…This is done by embedding an angioplasty balloon axially within the silicone parenchyma of the mock spinal cord at moulding. After it is cured and ready for use, one can then cyclically inflate it pneumatically [5] to replicate the small-amplitude pulsations. Additional improvements will eventually allow for simulation of the craniocaudal pulsations observed by Mikulis et al [13] which were found to be on the order of 0.4-0.5 mm, and for circulation of mock CSF in imitation of the slow, steady flow of actual CSF over the spinal cord surface.…”

“…To facilitate investigation of fixation techniques, we have preliminarily employed both in vitro [4,5] and in vivo [6,7] models of intradural implantation of our device, which is referred to in the literature as the Iowa Patch TM or I-Patch spinal cord stimulator. Our purpose here is to describe an improved version of our previous in vitro models, the design of which has been informed by the results from our in vivo studies.…”

Revisiting intradural spinal cord stimulation: an introduction to a novel intradural spinal cord stimulation device

“…We have also carried out studies of the biophysics underlying this concept, of the testing protocols, and fixation techniques used in in vivo experimentation, and of the histological evidence of safety with direct electrical stimulation of the spinal cord [5,6,9,12,13,21,23,24,29,33].…”