What does minimally invasive spine surgery really (MISS) mean?
The term “minimally invasive” is vague and nebulous. There is not a definition of what it is, so it’s hard to know if your spine surgery will be as minimal as possible.
It turns out that the question “What does Minimally Invasive Spine Surgery (MISS) Mean?” is a two-part question. The two parts are:
- The size of the incision, which reflects injury to normal tissues that happen to
surround the problem.
- The nature of the procedure (decompression, fusion, implant).
Why does the incision in open spine surgery need to be so big?
What really determines whether your doctor makes an incision that was 5 or 6 inches long or 1 inch long? The answer is whatever length it takes to expose and see the problem. Exposing the problem is only the first part of the operation, then you have to have enough light to see the problem. So let’s say that the incision started fairly small to expose the problem, but there was not enough light to see anything or do any work, so the incision had to be made larger to let some light in.
This is why retractors are used to to pull the muscles to the side. The surgeon would now has enough access and light to the problem (disc herniation or stenosis). The length of the incision depends on of the extent of surgery and the size of the patient – a heavier person, the thicker the skin and the larger the incision has to be (more exposure) to let enough light in to see.
One of the major drawbacks of open surgery is getting enough exposure to see what you need to see. Exposure requires pulling or retracting the muscles with a blade type of retractor and stripping the soft tissues off the bone.
I have assisted on hundreds of these surgeries and believe me; it is not a pretty sight. Even though the goal of muscle retraction is to help the surgeon see the problem area, the retractors can damage the muscles. When soft tissues get stripped off the spine, they don’t reattach like new.
What’s wrong with retraction?
Retraction can result in muscle and soft tissue injury with prolonged use. Muscle and soft tissue injury from retraction can lead to pain and long term (atrophy) after the surgery. Retraction pain defers from the back pain felt before surgery. Lots of soft tissue injury contributes to a lengthier recovery.
Why go “minimally invasive” spine surgery?
The concept is driven by the aspiration to reduce collateral soft tissue damage when performing any surgical procedure. It became popular in the 1980's when knee arthroscopy replaced the large surgical incisions for knee surgery. The benefits were obvious, smaller incisions, less bleeding, less pain, quicker recovery, and outpatient surgery. If you have to have your gall bladder removed today, you want a laparoscopic cholecystectomy (an endoscopic procedure) because it is less invasive for sure. It’s hard to know why endoscopic spine procedures have been so slow to catch on for the spine, when you think about how long knee arthroscopy has been around.
What do all “minimally invasive” techniques have in common?
No matter what the surgery, minimally invasive techniques can be attribute to one thing - the use of the tubular retractor. The tube replaces the blade retractor's to hold the soft tissues back, so the problem can be seen. That’s what “Minimally Invasive” means. It means using a series of tubes that go from small to large to retract the soft tissues, for the surgical exposure.
What determines the size of the tubular re-tractor?
Two things determine the size of the tube:
- The amount of light required for visualization.
- The size of the instruments needed to perform the surgical procedure.
That’s it, just those two things.
Visualization is the key, whether you use your eyes to look at a magnified picture through a microscope or a magnified image from a camera projected on a TV screen. Technology continues to improve the light sources, magnification and the size of the instruments to perform more precise techniques or procedures.
What determines the size of the incision?
The size of the tube does. Finally, we have a definition of what a“minimally invasive” procedure is. The diameter of the tubular retractor determines the incision size and there is a big difference in the incision size for a 7mm tube versus a 22mm tube. Although the skin can stretch, the incision must be slightly greater than the diameter of the tube. Don’t forget that the tube is just the retractor, we still have to get some light down to the operative field.
This is why instruments with a light source on the tip of the instrument (like a knee arthroscope) can use the smallest tube size and therefore have the smallest incision.
The size of the tube determines the approach that can be used to approach a painful spine condition. A smaller the tube provides more avenues and the options to get the to the problem, not to mention less soft tissue trauma and less scarring.
For example, a small 5 mm tube can approach a disc herniation in the lumbar spine through a transforaminal approach without any bone removal. This avenue is simply not an option with a larger tube. The transforaminal approach, which doesn’t require any bone removal, is less invasive than a procedure that requires removal of the lamina (laminectomy).
Another example is approaching a disc herniation at L5-S1 with a small tube that can fit under the lamina rather than removing a portion of the lamina (laminotomy).
How “minimally invasive” is the procedure?
You have to know the diameter of the tube used. There is a lot of difference of skill to perform surgery through a 26 mm tube than a 4 mm tube!
Endoscopic Spine Surgery with the laser is the ultimate in "minimally invasive spine surgery". The surgery is decompressive without a fusion.
And last but not least, remember that "minimally invasive spine surgery" doesn’t tell you what type of procedure you are getting. It’s key to remember the difference between a decompression and a fusion. A fusion can be performed through a tube these days, which I don’t consider a fusion a minimal type of surgery! Fusions are irreversible even when done through a small incision.
If any further questions arise about Minimally Invasive Spine Surgery please feel free to contact us.