Minimally Invasive Spine Surgery: Does the Evidence Support Its Use?

By Michael P. Steinmetz, MD

A large majority of patients who visit a spine surgeon are seeking a minimally invasive surgery (MIS) option. This approach to treating common spine disease has gained traction with patients due in large part to print and television advertising. One such consumer ad features attractive models, one of whom is sporting a small Band-Aid on her back with the caption: “Guess which one of these people had spine surgery today?”

In general, many types of surgeries have become minimally invasive. For example, most abdominal procedures have been replaced by outpatient laparoscopic options, including robot-assisted surgery. These same techniques have made their way into spine surgery —yet it remains unclear how effective they are or could be.

Defining minimally invasive spine surgery

The surgeon begins working through the minimally invasive retractor in order to remove a herniated disk in the lumbar spine.

MIS of the spine must first be defined; if not, essentially any operation performed through a small incision would be classified as minimally invasive. Technically speaking, in the spine, MIS involves making a small incision and a corridor through the muscle. This corridor is created by minimally dilating the muscle fibers en route to the spine.

This is in contrast to conventional surgery, which involves “stripping” the muscle from its attachment to the bone. The latter may be associated with more blood loss and certainly greater trauma to the bone.

With this definition in place, the only true difference between MIS and conventional surgery is the approach

The most commonly performed minimally invasive spine surgeries include lumbar microdiskectomy, laminectomy and transforaminal lumbar interbody fusion (TLIF). In the cervical spine, minimally invasive foraminotomy is also done frequently.

Potential for improved perioperative outcomes

Spine surgeons have been employing a minimally invasive approach to surgery since the 1980s. Unfortunately, we are only now collecting enough data to analyze the effectiveness of MIS for the spine.

After placing a retractor through the skin, the surgeon begins working through a 2.5 cm incision toward an eventual lumbar fusion with screws and rods.

It appears, albeit with early and low-quality evidence, that the vast majority of minimally invasive spine surgeries result in improved perioperative outcomes — specifically less blood loss, less pain immediately following the procedure and shorter hospital stays. However, long-term outcomes have not shown any advantages for MIS of the spine

Proponents of MIS tout the differences in perioperative outcomes as clear advantages, while opponents claim that the differences are not practical in “real life” and that analysis of long-term outcome data is necessary before we draw conclusions.

Studies have clearly shown that patients after MIS surgery have less pain and lose less blood during surgery. However, less pain may be 10 out of 100 on a pain scale versus 15. The difference between the numbers may be significant; however, these same patients’ pain may be practically the same.

Short-term advantages aside, research today has moved toward understanding the cost-effectiveness of minimally invasive spine surgery. If long-term benefits are not shown, then the early or perioperative benefits must decrease the cost of the entire healthcare episode. The evidence is extremely limited. Some early studies clearly have demonstrated cost-effectiveness, while others have not.

Intraoperative fluoroscopic image. A minimally invasive tubular retractor has been placed through the skin in the lumbar spine.

Mounting evidence of benefits, but more research is needed

Surgery as a whole is becoming more and more minimally invasive. Spine is no different. There are clear advantages and disadvantages to MIS of the spine. Minimally invasive spine surgery costs more, often takes longer to perform and exposes the patient to greater amounts of radiation due to more extensive intraoperative imaging. On the other hand, the incision is smaller, and the patient loses less blood, may have less pain and spends fewer days in the hospital.

MIS is appropriate for specific patients with specific pathologies, since one size never fits all. The decision to perform MIS or not largely rests in the pathology or the reason surgery is to be performed.

Evidence continues to mount demonstrating perioperative benefits of MIS over conventional spine surgery. We eagerly await the results of further outcome and cost-effectiveness studies.

Dr. Steinmetz is Co-Director of the Center for Spine Health in Cleveland Clinic’s Neurological Institute.