Minimally Invasive Surgery for Spinal Fusion: Superior to Open Surgery?Sometimes we joke that surgery has advanced to the point that brain surgery can be done on an outpatient basis with no overnight stay in the hospital. In fact, that's not far from the truth in some cases. Orthopedic surgery has also progressed to include minimally invasive (MI) techniques that no longer require an open incision. Hospital stays are greatly reduced with this approach.
There are many advantages to the minimally invasive techniques. Experts in favor of minimally invasive procedures say there is less soft-tissue trauma since the surgeon doesn't have to cut through all the layers of muscles and connective tissue. For the same reason, there is less blood lost and less chance the patient will need a blood transfusion. The patient's pain is less and the hospital stay is predictably shorter.
But there are still some studies that don't show a huge advantage to the minimally invasive approach and especially for spinal fusions. Some of the technical complications might suggest open incision is less risky. With minimally invasive methods, the surgeon has a limited field of vision so the procedure can take longer. Any increase in time under anesthesia has its own risks.
To help with the debate of which is better, orthopedic surgeons in China directly compared minimally invasive surgery for lumbar spinal fusion to the open incision technique. One surgeon performed all of the operations. Sixty-two (62) patients with degenerative lumbar disease were divided into two groups. Half the patients had a one-level lumbar fusion using a minimally invasive approach. The other half had an open incision fusion.
The actual procedure performed in all cases was a transforaminal lumbar interbody fusion (TLIF). The TLIF technique is used to avoid the problems that come with entering the spine from the front (anterior approach). Transforaminal means the surgeon gains access to the spine from the back and side. The surgeon makes a posterolateral incision and removes one of the facet (spinal) joints so the disc can be taken out.
Interbody describes how the fusion is circumferential (all the way around and from front-to-back). Once the disc is removed, the two vertebrae are distracted or pulled apart gently and a special device called an interbody spacer is slid into the disc space. The spacer helps restore normal disc height. A normal disc space takes pressure off the spinal nerve roots as they leave the spinal cord and pass through the opening formed by the vertebral bones.
When performing a minimally invasive TLIF, the surgeon uses a special tool called a tubular retractor system. A small incision is made through the skin and soft tissues to allow the placement of a hollow tube down to the spine. The tube holds the skin and soft tissues open. There is less risk of scar tissue formation using these tubes to push aside muscle fibers.
The tube gives the surgeon a working channel through the muscles without cutting and stripping them away from the spine. The surgeon passes instruments through the tube to perform the fusion. A tiny TV camera on the end of the instruments allows the surgeon to view (on a computer screen) what's going on inside the spine.
The exact steps taken in the minimally invasive procedure were described. Photos were provided of the incisions and retractors in place. Most of the fusions were done either at L4-L5 (very bottom of the lumbar spine) or L5-S1 (where the last lumbar vertebra connects to the top of the sacrum).
The authors used a wide variety of measures to determine the effectiveness of each technique and to compare outcomes. The very same factors named as "advantages" of minimally invasive surgery were the first units of measure. These included amount of blood lost during the operation, number of transfusions needed, number of days in the hospital, and intensity of postoperative pain. Other outcomes used to measure and compare results included length of time each patient was in surgery, number and types of complications, and how long it took to get the patient back up on his or feet walking.
Soft tissue injury was assessed using a particular lab value (blood test) called serum creatine kinase. X-rays of the spine were taken before and after surgery. Functional level was measured using a well-known test called the Oswestry Disability Index (ODI). Everyone was followed for at least two years. And the results? [Imagine a drum roll here].
In almost every measurement, the minimally invasive technique won out. There was less blood lost, fewer transfusions, less intense pain, and lower creatine kinase levels (an objective measure indicating less soft tissue damage). Patients in the minimally invasive group were able to get up and walk three days after surgery.
It took an average of two extra days for the open incision group to accomplish the same thing. Most of the difference in time-to-ambulation (walking) was credited to less pain from less nerve, muscle, and other soft tissue disruption in the minimally invasive group. As expected and predicted by other studies, the minimally invasive approach took longer by about one-quarter of an hour (15 to 16 minutes). With all the plusses of this procedure, this one minus isn't too bad.
In summary, recovery time was faster with less trauma to the soft tissues using the minimally invasive approach to transforaminal lumbar interbody fusion (TLIF). Pain levels and function were equal in both groups during the first three to seven days (one week post-op). There were some complications but these were isolated (only one patient with each complication reported) and apparently not specifically caused by the type of fusion procedure performed. The results of this study add to the evidence so far that the minimally invasive transforaminal interbody fusion (TLIF) is a superior technique over open incision TLIF.
Fan Shunwu, MD, et al. Minimally Invasive Transforaminal Lumbar Interbody Fusion for the Treatment of Degenerative Lumbar Diseases. In Spine. August 1, 2010. Vol. 35. No. 17. Pp. 1615-1620.
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