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Lumbar Discectomy: Minimally Invasive Spine Surgery

Micro Endoscopic Discectomy (MED)

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This article focuses on microdiscectomysurgery. To learn more about traditional (open) discectomy surgery, please read our article on percutaneous discectomy.


A patient is brought into the operating room and is put under general anesthesia. Some surgeons have chosen to perform microdiscectomy 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 created. Drapes are placed accordingly, and the surgery begins. See Figures 1, 2, 3, 4.

operating

Figure 1: Operating Room. An example how the operating room is setup for a lumbar microdiscectomy. 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.

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 split rather than separated from the bone.

By the time the fourth or fifth 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.
 
During a microdiscectomy, the surgeon may wear special glasses fixed with microscopes that provide optimal vision during the procedure. Other surgeons use a surgical microscope to magnify the tissues. Alternatively, the surgeon may use an endoscope (a camera) to help with the surgery. If the surgeon uses an endoscope, the surgery is technically known as a microendoscopic discectomy.
 
The endoscope, which is about as thick as the ink in a ballpoint pen, is attached to the edge of the working channel. 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. One disadvantage of an endoscope is that it only provides monocular vision. That means it’s like looking through only one eye. Depth perception is diminished in this technique.
?endoscope?

Figure 2: 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.

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.

?lamina?

Figure 3: 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 .

 

?lamina

Figure 4: Lamina Removal. A representation of the intraoperative area and the Kerrison rongeur removing the superior lamina. Copyright Medtronic Sofamor Danek. Used by Permission.

 

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. Sometimes the covering of the disc is already torn or even ruptured. 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 based on an excerpt from Dr. Stewart G. Eidelson's book, Advanced Technologies to Treat Neck and Back Pain, A Patient's Guide (March 2005).

Updated on: 10/08/13
Jason M. Highsmith, MD
This article was reviewed by Jason M. Highsmith, MD.
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