Minimally Invasive Spine Surgery: Do Benefits Outweigh the Risks?

Risks

Learning curve. Minimally invasive spine procedures are complex and surgeons experience a steep learning curve. "If someone is a spine surgeon already and comfortable with the techniques of spine surgery, then learning minimally invasive techniques is quite feasible," says Zachary A. Smith, MD, of Northwestern Memorial Hospital in Chicago. "The learning curve flattens out as you become more familiar with the new equipment and once the surgeon is comfortable, they are able to have similar results as with their open techniques."

However, what about those first few patients undergoing the minimally invasive technique?

"To limit risk, the surgeon must be competent in performing the minimally invasive technique," says Brian Grossman, MD, of Southern California Orthopedic Institute in Van Nuys. "This usually requires a fair amount of experience performing the same procedure using open technique. Some patients and some pathology may not be amenable to minimally invasive techniques. Surgeons need to recognize when the traditional approach would be more appropriate and utilize the technique that will allow him to predictably get the job done safely and expeditiously."

Damaged nerves. Smaller incisions don't necessarily mean better outcomes if the surgeon isn't able to visualize the surgical site appropriately or achieve the right correction.

"Some people think minimally invasive surgery just means a smaller incision and they can do less to achieve the same result," says Richard Kube, MD, Founder of Prairie Spine & Pain Institute in Peoria. "I have to be able to accomplish the same type of procedure through a smaller incision. If I'm fusing, I still have to remove the disc, decompress the nerve and insert the implants in appropriate positions and perform good bone grafting techniques. I can't short cut that."

Radiation exposure. A 2013 study published in Spine found that spine surgeons performing percutaneous endoscopic lumbar discectomy procedures reach the limit of allowable radiation exposure without a lead apron after 219 lumbar spinal discectomies per year. Surgeons with the apron are able to perform 5,379 per year safely.
 
"I use a C-arm fluoroscope and the radiation you get is proportional to the size of the case and number of cases you do," says Dr. Smith. "If you do a few cases, the radiation exposure is minimal. I use led glasses and led radiation gloves as well as techniques to keep my hands away from the field. Someone who is worried about radiation can also use the O-arm if their hospital has one because there is little or no radiation for the surgeon."

A study published in early 2014 shows using robotic guidance shortened procedure time and radiation exposure by 74 percent when compared with fluoroscopy guidance and 50 percent when compared with navigated augmentation.

"The downside [to minimally invasive spine surgery] at this time is the reliance with some procedures on radiation exposure to both the operating room staff and patient," says Alexander Vaccaro, MD, of Rothman Institute in Philadelphia. "Minimally invasive surgery will merge with navigational techniques to eventually avoid the need for excessive fluoroscopy in the operating room."

Benefits

Less pain. Patients undergoing minimally invasive procedures often report less pain than open procedures because less of the natural anatomy is disrupted. "I think the main benefit is minimally invasive spine patients have less pain and ambulate faster," says Dr. Smith. "They stay in the hospital fewer days and can return to work more quickly. Minimally invasive procedures take a surgery that could be a dramatic event and makes it have less of an impact."

Lower infection and complication rate. A smaller incision intuitively reduces the risk of infection. Surgeons also report fewer deep vein thrombosis issues and postoperative complications because the patients are able to move more quickly after surgery.

"As someone who did open surgery and converted to minimally invasive surgery, we never had a big infection rate, but with a smaller incision your infection rate will be lower," says Dr. Kube. "Additionally, it's been years since I've had patients treated with DVT. I used to be worried about those things, but I don't see it much now."

Less blood loss. Smaller incisions also mean less blood loss, which can ultimately improve outcomes. "I do fewer blood transfusions now than I used to," says Dr. Kube. "I wouldn't expect someone to have a blood transfusion for one or two levels at this point. As a result, we are able to perform fusion on patients who go home as outpatients."

Shorter surgical time. Eventually, the shorter OR times mean increased efficiency and patients spending less time under anesthesia. "In my practice, MIS can decrease surgical time when the surgeon is proficient," says Paul Jeffords, MD, of Resurgens Orthopaedics based in Atlanta. "I had to take time out of my practice for the appropriate training and for the first year it took longer than the open procedures, but now my minimally invasive procedures are done in a shorter time. Surgeons starting out must be willing to make a large commitment to learning the techniques and incorporating them into their practice."

Do risks outweigh the benefits?
Each surgeon gauges risks and benefits of minimally invasive surgeries differently. "More studies are being published that show the benefits of MIS surgery, but more research is needed," says Dr. Jeffords. "It's important that the individual surgeon decide with each patient which technique is best. In many cases, there is a good MIS option available for the patient, but in other cases a larger operation may be more effective.  Also, what works best in one surgeon's hands isn't necessarily what works best when performed by other surgeons."

MIS techniques also show benefits for revision procedures. "The benefits of minimally invasive surgery outweigh the risks in the setting of revision procedures which require only posterior thoracolumbar instrumentation, avoiding the need for open dissection necessary to expose the posterior elements," says Dr. Vaccaro. "Minimally invasive surgery may be beneficial at the superior end of the large posterior instrumented construct to avoid soft tissue disruption which may predispose to proximal junctional breakdown."

New technology could also close the gap between how comfortable surgeons are with minimally invasive versus open procedures.

"There are a lot of promising technologies that are coming down the pipeline," says Dr. Jeffords. "We have to be cautious and wait until there are proven outcomes for these studies before they are widely used. Also, at some point, as the size of the incision becomes smaller-and-smaller, the added benefit levels off as the risk increases.  For instance, there may not be a clinical benefit to performing spinal fusion through a 1 cm incision as opposed to a 1 inch incision, but the risk of complication or failure may go up considerably."

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