Anyone thinking about having a minimally invasive (MI) spinal surgery will find the information in this review article of interest. In fact, surgeons performing this type of surgery will benefit from the detailed presentation of MI surgical techniques as well. Procedures discussed include tubular microdiscectomy, hemilaminectomy, and interbody fusion.
The authors also present information on the placement of screws used in fusion to hold the spine in place, a process called fixation or instrumentation. A brief history of minimally invasive development as well as a summary of the advantages and disadvantages of this approach are also provided.
For those who don’t know what minimally invasive spine surgery means, it is a way to reach the spine through the skin and soft tissues without cutting through all the muscles and many tendons. Instead of a large, open incision the surgeon makes small slits in the skin and slips a tube down to the target site (usually vertebral bone or disc).
Surgical tools needed to perform any of the procedures mentioned reach the target tissue through the tube. A tiny TV camera on the end transmits real-time pictures to a screen to guide the surgeon. That sounds very simple and in a way, it is (compared to open incision and dissection or cutting through all the soft tissues).
The replacement of self-retaining retractors (used during an open procedure) by the tubular retractor (used during a minimally invasive spinal surgery) was a major turning point in spinal surgery. The self-retaining retractors pulled the soft tissue apart after incisions were made. This allowed the surgeon to gain access to the spine.
But the force of the self-retaining type of retraction caused crush injuries to the muscles, blood vessels, and nerves. Replacement with the tubular retractor changed all that. Loss of blood supply to the muscles and damage to the nerves often meant the patient never regained the muscle strength needed to support the spine. The result was often chronic back pain and weakness, a condition referred to as failed back surgery syndrome.
But there are many preparatory steps that must be taken by the surgeon before making even the tiniest incision. X-rays and MRIs are studied to give the surgeon detailed information about the patient’s anatomy. The exact entry point for the tubular retractor and its pathway to the spine is carefully mapped out.
Patients are placed in different positions depending on the planned procedure. For example, a prone position (face down) may be used when performing surgery with a posterior approach (from the back of the spine).
In other cases, the surgeon may reach the intended disc from the side or lateral approach. Patients are placed on their side for that type of procedure. The surgical table can move dropping the patient’s legs down in order to open up the space between the pelvic bone and the spine.
Again, the surgeon uses imaging studies to plot out the best place to enter the spine. Proper positioning is the key to a direct approach and accurate placement of surgical tools. And all of this helps avoid muscle injuries, especially preserving ligaments and protecting the deep muscles that help stabilize the spine.
Studies show that even at the cellular level, the goals of minimally invasive spinal surgery (to reduce soft tissue injury and speed recovery) are met. Blood studies show that all levels of biomarkers for tissue injury return to normal much faster after minimally invasive surgery.
As more surgeons receive the necessary training and practice in minimally invasive spinal surgeries, results improve. Likewise, the application of minimally invasive approaches expands. In other words, this technique can be applied to many more patients with a wide range of problems from stenosis (narrowing of the spinal canal) to scoliosis, disc degeneration, and spinal fusion.
Spinal fusion can be done from the side now (lateral approach) with far less disruption of the soft tissues and without cutting through the bone. Single-level or multiple-level fusion can be done using minimally invasive surgery.
There are some drawbacks to minimally invasive surgery (MIS) and some potential complications. Surgeons who are not doing MIS say it is because the opportunity to learn this technique is limited. Intra-operative and post-operative problems are much higher when the surgeon is gaining experience. The technical difficulties can be overcome with training and practice but it takes time.
In summary, minimally invasive spinal surgery is replacing the traditional open incision approach. There is more and more evidence to support minimally invasive procedures. Studies show that patients recover faster with less time in the hospital and fewer costs. They return to daily activities and work sooner, too. In the hands of a skilled surgeon, the procedure is safe and effective with less tissue damage, less blood loss, and less post-operative pain.