Custom rods take guesswork out of spine surgery

Reduced risk, improved results with personalized approach
December 16th, 2015

The ghostly spine in the X-ray image looks like the track of a looping coaster at Elitch Gardens or a road Dr. Seuss might have sketched in one of his more fanciful moments. It belonged to a patient with severe scoliosis. Thanks to a new technology that’s taken the most medieval – and, ultimately, most pivotal – minutes out of advanced reconstructive spine surgery, the patient’s backbone is now a lot less contorted.

It’s also a lot more functional, said Evalina Burger, MD, the University of Colorado School of Medicine spine surgeon who, with colleague CJ Kleck, MD, operated on the man a couple of months ago.

UNiD rods in a UCH operating room.

“He’s able to walk,” Burger said, considering the before-and-after X-rays on a screen in a busy nook of the Spine Center at University of Colorado Hospital. The success is the product of what might be considered an approach to personalized medicine.

More than metal rods

The technology in question is a software package combined with a metallurgical service that yields a pair of roughly 16-inch-long titanium rods. Metal rods – technically speaking, spinal osteosynthesis rods – have been mainstays in spinal surgery for decades, to realign and support stenotic, kyphotic, scoliotic and other painful, debilitating conditions that affect spines.

The metal rods can be short, supporting a couple of vertebra, or they can span much of the spine. So it is with Medicrea’s UNiD patient-specific spine implant, the name for these particular metal rods. They are different than previous metal rods because spine surgeons needn’t pause during a major, open surgery to play the role of metalworker. UCH is the only hospital in the region using them.

Until November 2014, when the U.S. Food and Drug Administration approved the UNiD, osteosynthesis rods arrived in the OR arrow-straight. Then, in the operating room, with the patient open on the table, surgeons estimated the ideal shape of a matching pair of rods and then employed an instrument called a French bender to create a supportive shape.

There were a couple of problems with this. First, having to bend rods during surgery prolongs OR time (and with it, risk of infection) by 30 minutes to an hour, Kleck estimates. Second, the French bender can only bend a rod so far, and some spines demand deeper rod-bends than the tool can deliver. Third, and most importantly, manually bending a rod sharply increases the chances that it will break. Burger, who has had a long-standing research interest in the metallurgy of spinal rods, explained it this way.

Evalina Burger, MD, calls a new spinal implant a “template, a guide during surgery”.

“If you bend any metal manually, you cause notching, which is metallurgically very important because it changes the characteristics of the titanium at that spot and makes it more fragile, so you get fretting and fragility fractures,” she said.

Real consequences

On a flat screen rotated vertically, Kleck pulled up a radiograph of a patient with a rod break. It had snapped at the deepest bend in the lumbar. A broken spinal rod like this requires a “revision surgery,” in this case not to fix the spinal problem, but rather a problem with the solution.

“When we pulled it out, the break was right where the notching was,” Kleck said.

Rod breaks are bad for patients and the health care system, and they have been happening a lot: in the United States, about 25 percent of the time, Burger said, though the UCH Spine Center’s rate of 14 percent is a lot better.

Burger’s colleague, CJ Kleck, MD, says the new implant reduces the risk of a spinal rod breaking.

They’ve had no rod breaks since they started using the UNiD more than a year ago, she added. It’s become the standard of care for complex spine corrections at UCH, with 40 surgeries complete or on the docket as of early December.

Software called Surgimap is the critical enabler. Burger and Kleck use it to digitally mark-up X-rays, calculating precisely what rod curvature is needed based on when the patient is in a natural, vertical position – as opposed to lying prone on an OR table, an orientation in which, as Burger put it “all the parameters change.” They send the file off to Medicrea, where the French company manufactures a pair of rods to those exact specifications, returning it to UCH less than a week later.

The UCH Spine Center was an early adopter of the UNiD, thanks to Burger’s familiarity with Medicrea, with which she has had a consulting agreement. She said that, in addition to improved OR efficiencies and reduced risk of rod breakage, the system has “made a significant difference in what we plan and what we can more reliably achieve” in surgery. The combination of morphological guesswork and metallurgical improvisation has, in the past, occasionally led to spinal fixes that left patients leaning one way or the other and requiring surgical adjustment after the fact, she added.

“In the OR, it’s much less stressful because you know where you’re heading,” Burger said.

Now, rather than being a last-minute, high-risk variable, the rod is an extension of a well-mapped procedure.

“The rod becomes a template, a guide during surgery,” Burger said as she looked at another Seussian X-ray. “If you go to all that expense and time and resources and don’t correct the patient, you don’t gain anything.”

About the author

Since 2008, Todd Neff has written hundreds of stories for University of Colorado Hospital and UCHealth. He covered science and the environment for the Daily Camera in Boulder, Colorado, and has taught narrative nonfiction at the University of Colorado. He was a 2007-2008 Ted Scripps Fellowship recipient in Environmental Journalism at CU.

His latest book, "The Laser That’s Changing the World," tells the story of the inventors and innovators who saw, and ultimately realized, the potential of lidar to help solve problems ranging from smokestack-pollution detection, ice-sheet mapping, disaster recovery, and, ultimately, autonomous-vehicle guidance, among many other uses. His first book, "From Jars to the Stars," recounts how Ball Aerospace evolved from an Indiana jar company - and a group of students in a University of Colorado basement - to an organization that managed to blast a sizable crater in the comet 9P/Tempel 1. "Jars" won the Colorado Book Award for History in 2012.

Todd graduated with a business degree from the University of Michigan, where he played soccer, and with a master’s degree from the Fletcher School of Law and Diplomacy at Tufts University. Before becoming a journalist at the turn of the millennium, he was an IT and strategy consultant. He once spoke fluent Japanese and still speaks fluent German.

When not writing, he spends time with teenage daughters and wife Carol, plays soccer, and allows himself to be bullied by a puggle he outweighs by a factor of seven.