Because the spinal nerves, vertebrae and discs are located deep inside the body, any approach to gain access to the spinal area requires moving the muscle tissue out of the way. In general, this is facilitated by utilizing a small incision (s) and guiding instruments and/or microscopic video cameras through these incisions. Contrary to popular belief, lasers are very rarely used in MIS surgeries.
A number of methods can be used to minimize trauma during MIS surgery. Some of the more common techniques include:
This technique involves progressive dilation of the soft tissues, as opposed to cutting directly through the muscles. By using tubes to keep the muscles out of the way, the surgeon can work through the incision without having to expose the area widely. Sometimes, the surgeon will also utilize an endoscopic or microscope focused down the tube to assist with performing the surgery through a minimal access strategy. Once the procedure is complete, the tubular retractor can be removed, allowing the dilated tissues to come back together. Depending on the extent and type of surgery necessary, incisions can often be small.
Depending on the condition of the patient, it may be necessary to place instrumentation, such as rods and screws, to stabilize the spine or to immobilize the spine to facilitate fusion of the spinal bones. Traditional approaches for placement of screws requires extensive removal of muscle and other tissues from the surface of the spine.
However, percutaneous (which means “through the skin”) placement typically involves inserting rods and screws through relatively small skin incisions without cutting or dissecting the underlying muscle. With the aid of X-ray images, guidewires are placed through the skin and into the spinal vertebrae along the desired paths for the screws. Then, screws are placed over the guidewires and follow the path of the wires. These screws have temporary extenders that extend outside of the skin and subsequently removed after helping to guide passage of rods to connect and secure the screws.
In some cases — especially those involving the lumbar spine — approaching the spine from the side of the body results in reduced pain, due to the limited amount of muscle tissue blocking the way. This approach is typically performed with the patient on his or her side. Then, a tubular retractor docks on the side of the spine to enable access to the spine’s discs and bones.
Depending on the patient’s condition, it may be necessary to access the front portions of the thoracic spine, located in the chest and surrounded by the heart and lungs. Traditional access approaches often involve opening the chest through large incisions that may also require removal of one or more ribs. However, thoracscopic access relies on multiple small incisions through which working ports and cameras can be inserted to facilitate surgery.