Photograph of the intradural components of the HSCMS. The dural cuff is trimmed intra-operatively to the size needed to best seal the durotomy. The plane containing the lead loops is aligned along the longitudinal axis of the spinal cord.
Schematic illustration of the lead bundle passing through the durotomy seal and being anchored by the titanium mesh Oya strap that bridges the laminectomy gap, thus providing strain relief for the lead bundle and reducing the risk of fatigue and fracture of the wires. In early versions of the device, the lead loops were oriented transversely to the longitudinal axis of the spinal cord as shown here and in Fig. 5 . In the most recent versions, they are oriented longitudinally as in Fig. 1 .
(a) Force on the HSCMS as a function of compression of the lead-loop assembly. (b) The resulting pressure on the surrogate spinal cord as a function of compression of the lead-loop assembly.
Edge-on view of the titanium Oya strap with integral lead port. Its length is trimmed intra-operatively for exact fit to the laminectomy gap.
Precursor version of the HSCMS used as the control device in the chronic ovine test of the suspension system performance. This device is similar in form to those used in our early acute tests of intradural spinal cord stimulation, in which the leads exit the ends of the arms of the electrode-bearing membrane.
Intra-operative view of the durotomy in one of the chronic ovine studies, with the Oya strap in place across the laminectomy gap. The lead bundle is seen emerging from the center of the mesh.
(a) A/P radiograph of the control HSCMS in the sheep spinal column. The six electrodes on the device are shown in place across the transverse axis of the spinal cord. (b) Lateral view of the implantation site. The arrow indicates the subcutaneous portion of the lead, the circle is centered on the zone where the lead fracture occurred just above the vertebral body, and the triangle shows the electrode-bearing membrane on the spinal cord inside the laminectomy gap.
Lateral view of the subcutaneous lead of one of the test HSCMS devices, showing full mechanical patency of it down to and within the laminectomy gap.
Charge-balanced, bi-phasic stimulation waveform and parameters employed in the electrophysiology studies used to confirm chronic conductivity at the electrode-spinal cord interface.
Details of HSCMS devices implanted for chronic study in the ovine model.
Representative results of impedance measurements made on the HSCMS devices implanted in two of the chronic study animals.
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