Fig 1.
Schematic illustration of electrical stimulation system.
A) Wirelessly powered stimulation system for nerve stimulation in the iES group; magnified image showing the implanted cuff electrode (inner diameter 2 mm, outer diameter 3 mm, length 5.25 mm) situated on the sciatic nerve. B) Schematic of the completely implantable stimulation system. C) 7 × 7 mm copper electrode attached just above the femur bone and inner thigh and connected to NuEyne TPD-NH1 for stimulation in the tES group.
Table 1.
Material properties for simulation at 25 Hz.
Fig 2.
Electrode placed on 3D rat anatomical model, a big male rat, simulating experimental setup.
A) iES group simulation model; an enlarged image showing the cuff electrode placed on the sciatic nerve. B) tES group simulation model; block electrodes placed just above the femur bone and inner thigh (left) and a cross section showing the block electrodes attached to the skin and sciatic nerve (right).
Fig 3.
Temporal change in Sciatic Functional Index (SFI) in each group.
Functional recovery measured every week starting a week after surgery using the toe-spreading SFI. The dot lines on the graph was best fitted of SFI data points of each group using Boltzmann equation.
Fig 4.
Histomorphometric evaluation of sciatic nerve section.
Transverse nerve sections stained with toluidine blue from A) normal and B) each group over time. C), D) Axon diameter and g-ratio of each group over time represented in boxplot (solid line); individual data of each group were indicated as dotted boxplot; the inset graph showed improvement trends of axon diameter and g-ratio over time by linearly fitted lines. The horizontal line and square inside each box indicated the median and mean, respectively; the upper and lower borders of each box represented the first and third quartile; the whiskers indicated 1th and 99th percentiles. Bar = 50 μm.
Fig 5.
Histomorphometric evaluation of gastrocnemius muscle sections.
A) Transverse muscle sections from each group over time; black arrows indicate fibrosis. B) Transverse muscle section from normal rat with H&E staining; green polygon indicates myofiber. C) muscle fiber area of each group over time presented in boxplot; linearly fitted muscle fiber area enclosed in the graph. Bar = 100 μm.
Fig 6.
Simulated E-field and vector field distribution.
E-field distribution expressed on the cross section of the big male rat for A) direct stimulation case and C) TENS case; color map corresponds with the E-field intensity, with black as zero; and vector field distribution for B) direct stimulation case and D) TENS case; arrows indicate the direction of the E-field; the color of the arrow corresponds with E-field intensity. The cross section corresponds with the section shown in Fig 2B, passing through the sciatic nerve of the big male rat. Transparent tube represents the sciatic nerve.