Tache_Mulugeta_OT2OD024899_Thoracolumbar and sacral nerve roots acute electrical stimulation and colonic motility measurements

A midline abdominal incision was performed to gain access the peritoneum. Three colonic regions of interest -proximal/ascending, transverse, distal/descending - were identified and externalized.

Still-manometry probes (Mikro-CathTM diagnostic pressure catheter, #825-0101, Millar, Houston, TX) were inserted into the colon via a small incision and maintained in position with a loophole silk ligature.

Equipment

For the proximal colon, 4 manometry probes were inserted about 10 cm below the ceco-colic junction, at 10, 13, 16 and 19 cm from the point of entry. For the transverse colon, 4 manometry probes were inserted at the end of the proximal colon, at 10, 13, 16 and 19 cm from the point of entry. Distal probes were inserted in the distal colon through the anus with sensors at 10, 13, 16 and 19 cm proximal to the anal verge. One sensor was also added in the anal canal (2 cm from the anal verge).

The abdomen was then closed and the pig placed on his abdomen, leaving access to the back.

The S2-S4 sacral spinal nerves (S1/2 vs S3/4) or T10-L2 thoracolumbar spinal nerves were accessed via a laminectomy.(surgery time: 30 min-40 min).

Laminectomy is a common spine operation and refers to surgical removal of the vertebral lamina, thereby unroofing the vertebral canal. We followed similar processes as described in this reference.

Before surgery, we palpated the lumbar spinous processes along the midline and identified the vertebral levels of interest (T10-L2 or S2-S4). A midline incision using a scalpel/electrocautery was then performed and the subcutaneous tissue and fat dissected to gain access to the thoracolumbar or lumbosacral fascia, respectively. The fascia along the midline was cut to expose the supraspinous ligaments spanning between spinous processes. The supraspinous ligaments was open over a few millimiters. Then using a Freer elevator, the supraspinous ligaments was gently detached from spinous processes (subperiosteal dissection). The dissection was then extended to the interspinous ligaments up to the facet joints of the spinous processes along the area of interest. After locating the lamina, we opened the lamina using a surgical saw or a Kerrison rongeur to extract bone in a piece-wise fashion over the whole vertebral segment of interest in order to gain access to the ligamentum flavum, periosteum, epidural fat, and dura sac. The spinous processes corresponding to the region of interest were removed, allowing access to the meninges. The epidural fat was gently removed taking care not to damage the dura sac and allowing identification of the spinal roots.

During the surgical procedure and as the laminectomy was completed, hemostasis was performed with bipolar electrosurgery. Monopolar electrosurgery was not used because of the proximity of neural structures.

Bone wax was placed along sites of bleeding from exposed bone and absorbable hemostat dressing were used to obtain hemostasis near soft tissue. We also used cotton to wick serous fluid and blood away from the dissection where necessary.

The pigs were euthanized at the end of the experiment with an intravenous injection of pentobarbital (100 mg/kg).