Minimally invasive spine surgery, also known as MISS, is any minimally invasive procedure that targets conditions specifically within the spine through the use of small incisions as opposed to traditional open-spine surgery which typically requires a 5-6 inch incision. This technique utilizes modern technology, advanced imaging techniques and special medical equipment to reduce tissue trauma, bleeding, radiation exposure, hospital stays and recovery by minimizing the size of the incision.
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MISS can be used to treat a number of spinal conditions such as degenerative disc disease, disc herniation, fractures, tumors, infections, instability and deformity. It also makes spine surgery possible for patients who were previously considered too high risk for traditional surgery due to previous medical history or the complexity of the condition.
Methods
Traditionally, spine surgery has been performed using the "open surgery" method. This procedure requires surgeons to create a 5-6 inch incision down the affected portion of the spine and to pull back the tissue and muscle using retractors in order to reveal the bone. Open surgery can affect more anatomy than is actually required to operate on the spine and can lead to lengthier recovery periods.
Minimally invasive surgery aims to combat these issues by reducing tissue trauma, bleeding and risk of infection while improving the healing process of the body by minimizing the size of the incision.
Minimally invasive spine surgery is performed by an orthopedic surgeon and a trained medical team. Typically, they will begin the operation by delivering a type of anesthesia that numbs a particular part of the body in conjunction with sedation or simply give a general anesthesia that prevents pain and allows the patient to sleep throughout the surgery.
Next the surgeon will begin taking fluoroscopic images on the affected portion of the spine. This will allow them to see exactly what they're operating on, in real-time, throughout the surgery without creating a large incision.
At this point, the surgeon will begin performed the operation percutaneously, meaning "through the skin", by creating an incision of about 15mm above the affected portion of the spine. This will provide enough room to allow the insertion of a tubular retractor, a small, rigid tube, which will allow the doctor to put small operating tools down into the spine as well as endoscopic cameras and a light.
Next, the surgeon will make the necessary repairs to the spine, extracting affected disc material out through the tubular retractor and inserting devices (like screws) through the tubular retractor. Once the repairs have been completed, the tools and tubular retractor are removed from the back and the surgeon closes the incision using stitches, glue or staples.
Equipment
Special medical equipment is often used in minimally invasive spine surgery which allows surgeons to complete a procedure while affecting as little surrounding tissue as possible. One of the most common tools used is a tubular retractor. The tubular retractor is responsible for creating a small passageway down to the affected area of the spine, allowing the surgeon to insert small tools or an endoscope through the center of the device in order to see and operate without a large incision. Any disc or bone material that needs to be removed from the spine is taken out through the tubular retractor and any devices necessary for fusion, like intervertebral spacers, rods, pedicle screws, facet screws, nucleus replacement devices and artificial discs, can be inserted through the retractor.
Another tool frequently used in minimally invasive spine surgery is the endoscope. This instrument is a slender, illuminated optical that allows surgeons to look deep into the body while disturbing little of the surrounding tissue. In minimally invasive spine surgery, the endoscope is often placed through the tubular retractor.
Surgeons also use intraoperative fluoroscopy to help them aim retractors over the affected area of the spine, guide the accurate insertion of implants and assist in other various steps of surgery like decompression and discectomy. Fluoroscopes use X-rays to obtain real-time, moving images of the interior of an object or patient during surgery which allows physicians to see what they're operating on without creating large incisions. However, in recent years there have been concerns over the safety of fluoroscopic techniques. One of the most pressing is the fact that, during surgery, patients and operating room staff must be directly adjacent to the image intensifier and are exposed to radiation throughout the procedure. In order to combat this issue, doctors are advised to wear protective equipment, including lead aprons and thyroid shields, which can be cumbersome and inconvenient.
Robotic guidance is another technique that is used occasionally in minimally invasive spine surgery. A relatively new technology, robot-assisted surgery is aimed at reducing "human error" and increasing implant accuracy while reducing radiation exposure for operating room staff and patients.
Specific procedures
There are many spinal procedures that make use of minimally invasive techniques. These include:
Benefits
While the outcomes of minimally invasive spine surgery are typically similar to traditional open methods, the major clinical benefits of procedure are found in the short term. Reported outcomes of MISS often include:
Many consider cost to be another benefit of MISS. While upfront costs are typically higher than traditional surgery, mainly due to the complexity of the procedure and technology needed to perform it accurately, economic analysis tend to show that MISS is more cost-effective. This is often the case because MISS allows for shorter hospital stays, less prescription medication, less recovery time and lower reoperation rates for infection.
Risks
While minimally invasive spine surgery can offer numerous benefits, there are still risks involved in undergoing the procedure. One of the most prominent issues with the procedure is the learning curve that surgeons must overpass in order to properly perform the surgery. MISS is a complicated operation that requires precision and knowledge not needed in traditional open surgery. This being the case, surgeons need to have an extensive knowledge of minimally invasive procedures as well as the tools needed to perform them properly.
Another risk that patients face when undergoing minimally invasive spine surgery is the potential for damaged nerves. Since incision sites are so small, surgeons can occasionally have a difficult time seeing exactly what they're operating on and risk damaging the spinal nerves in the process.
Radiation exposure has been cited as another risk of minimally invasive spine surgery. Surgeons will often use fluoroscopic imagery throughout the procedure in order to see what's happening in real-time. However, since fluoroscopes use X-rays to penetrate skin, patients and operating room staff are exposed to radiation. Some studies have shown that spine surgeons who perform percutaneous endoscopic lumbar discectomy procedures reach the limit of allowable radiation exposure without a lead apron after 219 lumbar spinal discectomies per year. These lead aprons weigh about 7 pounds and can be cumbersome to the surgeon during operation.
As with any other surgery, there are additional risks. These can include:
History
Humans have been trying to treat spinal pain for at least 5,000 years. The first evidence of spine surgery appeared in Egyptian mummies buried in 3,000 BC. However, Hippocrates is often credited with being the father of spine surgery due to the extensive amount of writing and proposed treatments he produced on the topic. The first operative spine surgery is credited to Paul of Aegina who lived during the 7th century.
However, only within the last 50 years have advances in digital fluoroscopy, image guidance, endoscopy and minimally invasive surgical tools allowed minimally invasive spine surgery to rise to the forefront of spinal procedures.
Some of the first advancements in minimally invasive spine surgery came from attempts to improve visualization for physicians during operations. In 1931, Dr. M.S. Burman first introduced the idea of myeloscopy which allowed for direct spinal cord visualization by drilling a small hole in the base of the sacrum. Several years later, in 1938, Dr. J.L. Pool expanded on this idea and first introduced the concept of intrathecal endoscopy, which involves inserting the endoscope directly into the spinal canal. While groundbreaking, this procedure became increasingly unpopular due to morbidity associated with inserting a large-bore scope into sensitive dural cavity. Eventually, in 1973, Dr. Satoh Ooi used an endoscope to to examine the intrathecal space before the operation and was able to see pathological features in greater detail.
Another milestone in minimally invasive spine surgery came in 1941 when Eugene Janson and Arnold Balls discovered chymopapain in an attempt to relieve the pain caused by herniated discs. They found that certain properties from the Carica papaya fruit could cause depolymerization of the proteoglycan and glycoprotein macromolecules in the nucleus pulposus. Dr. Smith adapted these laboratory discoveries into a clinical setting and performed the first chemonucleolysis procedures on humans in 1969, which is considered to be the first minimally invasive spine surgery. This procedure involved injecting chemical chymopapain in the annulus fibrosus, or the tough outer layer of a disc, and removing the herniated disc through enzymatic hydrolysis. However, despite FDA approval, enthusiasm for the procedure dwindled after several reports of complications, including arachnoiditis, were published.
Tubular access to the spine was first introduced in 1991 by Drs. Faubert and Caspart, which effectively paved the way for further development of tubular retractors and other smaller instruments.
Communities
Minimal invasive spine communities were founded by groups such as ISMISS, WCMIST, PASMISS, IMLAS, ITSS, Wenmiss and AAMISS. One of these groups, ISMISS, was founded by Kambin, Schrieber and others in Zurich.