MicroEndoscopic Discectomy (MED)
A patient is brought into the operating room and is put under general anesthesia. Some surgeons have chosen to perform MED under local or spinal anesthesia allowing the patient to stay awake throughout the procedure. The patient is turned onto his abdomen and padded into position. A fluoroscope (floor-o-scope, a machine which projects live x-ray pictures onto a screen) is brought in for use during the remainder of the operation. The patient's back is scrubbed with sterile soap, and a sterile field is cre-ated. Drapes are placed accordingly, and the surgery begins. See Figures 10-A, B, C, D.

Figure 10-A: Operating Room. An example how the operating room is setup for a lumbar MED. The surgeon stands on the side of the ruptured disc. The television monitor is across the table. For the majority of the operation, the surgeon performs the surgery while watching it on the screen. Copyright Medtronic Sofamor Danek. Used by Permission.

Figure 10-B: Endoscope. A representation of the working channel once the serial dilators have been removed and the endoscope is placed. Copyright Medtronic Sofamor Danek. Used by Permission.

Figure 10-C: Lamina. A representation of the area of lamina that needs to be removed to visualize the nerve and the disc rupture. Copyright Medtronic Sofamor Danek. Used by Permission .

Figure 10-D: Lamina Removal. A representation of the intraoperative area and the Kerrison rongeur removing the superior lamina. Copyright Medtronic Sofamor Danek. Used by Permission.

The disc space is confirmed using the fluoroscope, and a long acting, local anesthetic is injected through the muscle and around the bone protecting the disc. A half to one-inch incision is made. A thin wire is placed through the incision and lowered until it touches the bone. Progressively larger dilators are brought down on top of one another following the wire. In this manner, the muscle is stretched rather than cut. By the time the 4th or 5th dilator is placed, the muscles are stretched to an opening roughly the size of a nickel. It is through this opening that the procedure is performed. Over the last dilator, a working channel is positioned; this circular retractor holds back the muscles and now the dilators can be removed. The retractor is held in place by a mechanical arm attached to the table.

Finally, the endoscope (en-doe-scope) is attached to the edge of the working channel. The endoscope is a camera about as thick as the ink in a ballpoint pen. It projects an image of the base of the working channel blown up to the size of the TV screen. This allows for microscopic manipulation and removal of the tissues.

When a small amount of muscle is left over the lamina (lamb-in-ah), or exposed bone, this is cleaned off. In order to access the nerve, this roof of bone must be removed; this can be done with a small, high-speed drill or a small bone-biting tool called a Kerrison rongeur. The bone just below the endoscope covers the nerve, as it is about to exit the spine. By removing the bony cover, the nerve can be exposed and then safely moved away. After the bone is removed, the yellow ligament (a rubbery layer of tissue) can be seen which protects the underlying nerves. All the nerves, except the exiting nerve, are grouped together in the thecal sac where they float loosely in spinal fluid.

Care is taken as the yellow ligament is separated and removed, exposing the thecal sac and the exiting nerve root. A very small retractor is placed just on the outside of the root, and the nerve and thecal sac are moved together. Directly below the retractor lies the ruptured disc.

Ruptured disc material has a consistency similar to uncooked shrimp. When a small puncture is made into the tissue covering the disc, the disc will often times begin to ooze out. Various tools are used to remove the ruptured disc and other loose fragments of disc in the surrounding area. No attempt is made to remove the entire disc at that level - that is what is supporting those vertebrae. When completed, the small hole will fill in on its own. The case at this point is essentially finished.

The wound is irrigated with antibiotics. As the scope is withdrawn, your surgeon can see the tissues coming back together. A stitch or two is placed at various levels to hold the tissues together to help healing. Typically, buried stitches are used to close the skin, and none need to be removed at a later date. Commonly, Steri-Strips® (small sterile tape) and a loose bandage are applied to the wound. The patient is then positioned on a stretcher, woken up, and sent to the recovery room. In a few hours, if all goes well, he or she may leave the hospital.

This article is an excerpt from Dr. Stewart G. Eidelson's book, Advanced Technologies to Treat Neck and Back Pain, A Patient's Guide (March 2005).

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