Basic Introduction to Minimally Invasive Spine Surgery

Thoracoscopic, laparoscopic, endoscopic, “through the scope”, minimally invasive? These terms describe recently popularized approaches to spine surgery. In order to understand how these approaches may have a role in your spinal surgery, the terminology must be understood.

Endoscope

An endoscope is an instrument used for the examination of a hollow viscus such as the bladder or a cavity such as the chest. The endoscope is basically a camera mounted on a long thin lens with a cable and a light source. The light source is mounted onto the lens and provides light to illuminate the field to be visualized. The cable mounted on the camera connects to a TV screen, which displays the camera’s field of focus.

Figure 1: Endoscope with Camera and Light Source

 

Figure 2: Endoscope and TV Monitor

Endoscopy, Thoracoscopy, Laparoscopy

Endoscopy is the visual inspection of any cavity or hollow viscus by means of an endoscope. Thoracoscopy is the visualization of the thoracic cavity or the chest. Thoracoscopy is used to assist in procedures on the heart and lungs. Laparoscopy is the visualization of the abdominal cavity. Laparoscopy is used to assist in procedures on the intestines, stomach, or removal of the gallbladder.

What is the purpose of utilizing the endoscope? The endoscope allows the surgeon to have an illuminated and magnified view of the operating field without having to make a large incision. With the assistance of the endoscope surgeons can utilize several small incisions to perform the same procedure they would otherwise perform using a single large incision.

 

Laparoscopic and thoracoscopic surgery are not new techniques. Dr. Jacobaeus was the first to publish his work in 1910 on both of these topics. In the 1980’s laparoscopic cholescystectomy or removal of the gallbladder became very wide spread. However, it was not until the early 1990’s when the application of these techniques became utilized in the field of spinal surgery. Early uses were for biopsy, removal of thoracic disc herniations and releasing or mobilizing the anterior spine for scoliosis and kyphosis. The applications rapidly expanded to many aspects of spinal surgery.

Instrument Availability

Unfortunately just the existence of the endoscope does not automatically allow the spine surgeon to perform surgery endoscopically. First, the surgeon must first recognize if the surgery can be performed without a formal incision. Currently only a small number of spinal surgeries can be performed utilizing an endoscopic approach. Once deciding to perform the surgery endoscopically, the surgeon must determine if all of the instruments and implants (screws, rods, and cages) are available to perform the surgery. You may ask, if the surgery is now being performed with a formal incision, are not all of the tools and implants needed to perform the surgery already available? The answer to this is unfortunately no. Instruments used for endoscopic surgery differ from the instruments used to perform surgery through a formal incision.

Endoscopic Instruments

When a surgery is performed with a large incision the dissection leads the surgeon directly to the spine. The approach enables the surgeon to touch the spine and manipulate the spine manually as is often necessary. Instruments for performing open surgery are traditionally made short allowing the surgeon better control and tactile feel. The implants and the tools used to insert the implants are often very large and bulky, because the incision size allows a large access.

Figures 4 & 5: Endoscopic Instrumentation

In developing the endoscopic approach for spinal surgery, the first task was to develop longer streamlined instruments. New and different instruments needed to be developed to perform tasks that were normally done with the surgeon’s hands on the spine, but now must be performed at a significant distance from the spine. As these instruments were developed basic procedures could now be performed endoscopically. As the technique progressed the desire to instrument the spine became the next step. We needed to develop implants that could fit through small incisions and the instruments to insert and manipulate the implants that would fit through the same portals.

Endoscopic Portals

Portals are devices that provide a passage through which the surgeon operates. The incisions for endoscopic surgery are usually a centimeter in length. Once the skin incision is made an instrument is used to continue the dissection into the cavity, usually the chest or abdomen, depending the incision location and the patient’s body this can be a fairly long distance. When the instrument is removed all the tissue falls back into place and the opening into the cavity can be very difficult to find. In order to avoid damaging the tissue by moving instruments in and out of the passage, a portal is placed into the incision to hold the tissue apart.

There are two main designs of portals, open or sealed. The open portal is an open tube that allows for the passage of air from outside of the body to inside the cavity and acts only as a spacer. The sealed portal limits the passage of air or gas into or out of the cavity. This type of portal is often used in the abdominal cavity, this allows for the cavity to be expanded allowing the surgeon space to operate. The portals used in the thoracic spine tend to be 11 to 12mm, while portals used in the abdominal cavity tend to be larger. All of the instruments and implants had to be made to not only fit through these small passages, but also perform their function once inside the cavity.

Operating Space

In the thoracic spine the space to operate through is provided by deflating the lung. The anesthesiologist performs this by placing a special breathing tube down the trachea into the large airway of each lung. Once in place the patient is asleep and breathing with only one lung, which is very safe and commonly done. This allows the opposite lung to deflate and falls out of the way of the spine. The portals are placed and the procedure to be performed on the spine is begun. While in the thoracic cavity the lung is collapsed for space, in the abdomen the cavity is filled with CO2 gas creating the operating space.

 

The goal of endoscopic surgery must be the same as surgery performed with a formal open procedure. The incision and tissue dissection to the spine may be less, but the surgical procedure cannot be less. Advantages of endoscopic surgery include: improved postoperative recovery, decreased pain, and faster return to activities. These findings have been demonstrated in many, but not all endoscopic procedures. Even today only a small percentage of spinal conditions are suitable for endoscopic surgery. Do not hesitate to discuss with your spine surgeon if your particular condition is amenable to an endoscopic approach.