The Evolution of Spine Surgery: Minimally Invasive Techniques and Artificial Discs

Advancements in technology and better knowledge of spinal biomechanics have led neurosurgeons to adopt techniques that are minimally invasive and restore the normal function of the spine. These techniques can result in less pain, faster recovery times, and fewer complications for patients.

“Neurosurgery is a very technologically driven specialty,” said Barrow Neurosurgeon Dr. David Fusco. “We’re treating spinal fractures and degenerative diseases like we were in the 1960s and 1970s, only we’re doing it in ways now that allow for greater surgical efficiency, greater patient safety, and better long-term outcomes.”

Minimally Invasive Spine Surgery

Improvements in microscope technology and image-guided navigation, along with the goal of making spine surgery less painful, led to the development of a spectrum of minimally invasive surgical techniques for the spine.

“With open surgery, you go through so many muscles in the back, and that tissue dissection is actually what contributes to people’s pain the most,” said Barrow Neurosurgeon Dr. Laura Snyder, who specializes in minimally invasive spine surgery. “So, I think people just started to say, ‘What if we look at it another way?’ ”

Minimally invasive techniques may include the use of tubular dilators, which allow neurosurgeons to spread the muscle tissue apart rather than cut through it. Once the dilator is removed, the muscle tissue returns to normal.

Neurosurgeons have also started performing certain procedures by approaching the spine through the side of the body, where there is less muscle tissue compared to the back.

In addition, improvements in microscope technology and image-guided navigation have allowed neurosurgeons to use smaller incisions.

Minimally Invasive Spine Surgeon Dr. Laura Snyder

“Twenty years ago, when pedicle screws or hardware were placed in the spine, X-ray imaging was used,” Dr. Fusco said. “From X-ray imaging came intraoperative navigated CAT scans, where you have a CAT scan of a patient that you’re able to use in surgery correlated with the patient’s anatomy that allows you to direct very specific trajectories for all your hardware. You can see exactly where things are going in a three-dimensional view.”

Dr. Snyder noted that while the best treatment approach depends on the patient and specific disease, there are many conditions that can be treated with minimally invasive surgery. These conditions include disc degeneration, disc rupture, disc herniation, spinal stenosis, spinal instability, bone spurs, small tumors, and some scoliosis cases.

Dr. Snyder said while minimally invasive techniques have been around for more than a decade, they have improved and become more accepted due to research showing good outcomes.

“The aim of minimally invasive spine surgery is to decrease muscle and tissue trauma,” Dr. Snyder said. “When you do that, patients end up having less blood loss, less post-operative pain, and faster post-operative recovery when compared to the open techniques.”

She also said neurosurgical training already lends itself well to minimally invasive spine surgery.

“Neurosurgical training allows you to become very comfortable with microsurgical techniques because you’re using the microscope all the time in very small spaces and around very important nerves,” she said.

Artificial Disc Surgery

Neurosurgeons have also been exploring alternatives to spinal fusion that allow them to restore the normal anatomy of the spine when treating instability and degeneration.

“Our current algorithm is to re-establish the normal orientation of the spine and to fixate the joints so movement is no longer present and pain is eliminated,” Dr. Fusco said. “But we know that eliminating the mobility of the spine can have longer-term consequences on the joints that were not part of the surgery. You could subsequently predispose people to future surgery.”

Some neurosurgeons are using joint replacement surgery, called arthroplasty, to treat instability and disc degeneration.  The problematic vertebral disc is completely removed and replaced with an artificial disc.

“Much like replacing a worn-out hip or worn-out knee, we are able to replace the joint of the spine and preserve the range of motion,” said Barrow Neurosurgeon Dr. Steve Chang, who specializes in artificial disc surgery. “Ultimately, this helps to minimize the stresses on the adjacent levels that are not treated.”

The artificial disc consists of a biomedical-grade plastic device sandwiched between two titanium endplates and is designed to last a lifetime.

Expandable retractors are inserted through small incisions over the vertebral pedicles to treat a collapsed disc in the lumbar spine while minimizing muscle dissection.

Dr. Chang said better knowledge of spinal biomechanics – the study of the forces and movements in the spine – is one of the main reasons artificial discs are available today.

“We have a better understanding of the normal dynamics of the spinal column from a biomechanics point of view, and engineers have designed these products now where they are able to more closely represent what a normal neck moves like,” he said.

But Dr. Chang said he tells patients that the biggest disadvantage with total disc replacement is the lack of data available for the devices because they have not been used for very long.

“We don’t have the 30-year data that we do for fusion,” Dr. Chang said. “We know what fusion is going to look like in 30 years. We are beginning to get longer-term data in that five-,seven-, and 10-year range for the first-generation devices, but these devices have continued to improve to mimic the normal anatomy. With each generation, we don’t have that 30-year data that we do for fusion.”

Artificial discs have also not shown as much success in the lumbar spine as they have in the cervical spine, and some patients with very severe degeneration may not be good candidates for total disc replacement.

But Dr. Chang expects artificial disc surgery to become more successful over time.

“We learn from our experiences through big data,” he said. “As we accumulate this experience using these devices, we’ll be able to improve on the next generation.”

Related: The Evolution of Spine Surgery: Ancient Egypt to the Present