Lumbar spinal stenosis, or the narrowing of the space where the spinal nerves exit between the vertebrae in the lower back, is among the most common reasons for spine surgery in aging patients. But despite the prevalence of the condition, lumbar decompression surgery and the rigid instruments employed to perform the procedure have changed little in recent years and can even compromise the integrity of surrounding joints. Frustrated with this outdated approach, board-certified anesthesiologist Jeffery Bleich cofounded Baxano Inc. (San Jose, CA) in 2005 to develop and commercialize the iO-Flex system, a suite of flexible instruments designed to achieve decompression while preserving bone and tissue.
Using traditional rigid instruments, spinal surgeons may be forced to remove part, or all, of the facet joint--the small, stabilizing joints found on either side of the spine--in order to adequately decompress tissue on the spinal nerves. As a result of this excessive removal of bone and tissue, patients could experience spinal instability, accelerated disc degeneration, or the need for spinal fusion, according to Michael Wallace, senior vice president of R&D and operations at Baxano. "The iO-Flex system, however, was developed as a way to get a complete lumbar decompression of the central, lateral-recess, and foraminal tissues for spinal stenosis patients without compromising the integrity of the facet joint," he says.
Touting the tag line "precision decompression from the inside out," the iO-Flex is a three-step, flexible 'over-the-wire' system that provides access, confirmation, and decompression. To gain access to the area, the surgeon places and deploys a proprietary probe midline into the back and out the foramen. A guidewire is then deployed through the probe and back up through the patient's skin. Once the probe is removed, the surgeon attaches the Neuro Check device to the guidewire and inserts it to confirm that the wire is positioned dorsal to the nerve root. Finally, the Neuro Check device is removed and, using the wire, the MicroBlade Shaver is brought into the foramen for precise removal of impinging bone and tissue.
Achieving this ability to precisely remove impinging bone and tissue required extensive design and development work on an extremely tight schedule. While its engineers labored over the mechanical design of the iO-Flex, Baxano enlisted the help of consulting firm IDEO (Palo Alto, CA) to optimize the system's industrial design and user experience in terms of ease of use, ergonomics, and safety.
"Our process is user-centered design, so we go into the field and talk to the end-users and the people who will be using the equipment and would be most impacted by it," explains John Lai, industrial designer and iO-Flex project lead at IDEO. "We get their insights, then rapidly create improvements in prototypes and quickly get prototypes back in the users' hands for more feedback." For the iO-Flex system, IDEO observed multiple live surgeries, spoke with surgeons, and organized surgeon workshops. The latter approach consisted of having surgeons evaluate multiple prototypes, provide feedback, and then test the prototypes in a cadaver lab.
During these reviews, Lai notes, it quickly became evident that doctors exhibited different preferences in the use of the probe component during the access step; some used one hand while others employed both hands. "The probe solution looks very simple and elegant now, but at the time, we wanted the device to be able to be actuated with either one hand or two hands," Wallace of Baxano says. "The challenge was being able to design the right interface on the handle and the plunger deployment element so it had the flexibility of accommodating either one-hand or two-hand use without making it subpar for one method."
IDEO managed to meet this need for one- or two-handed use while also enhancing safety. "Because you're pulling things in and out of the body, the probe has these flared handles. So, when you're pulling the probe, you have something for your hand or fist to pull against so it doesn't slip," Lai says. "We provided a lever on top that had another flare so that you could either push or pull on that. It provided surfaces and a shape that allowed you to push or pull without too much effort, using either one or two hands."
Ergonomics and visual and tactile cues were also critical factors in the design of the probe device. The initial design featured rectangular profiles, which did not clearly indicate which side was up, according to Lai. "Part of the core design was this identity of having very discreet visual and tactile cues for what was up and down," he says. "We observed that it was very important for the surgeons to know and for the team that was working around them to see that they were using the tools correctly."
With this in mind, IDEO visually differentiated the top and bottom of the device through the use of high-contrast designs marked by a distinct color scheme. The team also reworked the shape of the probe so that it conformed to the surgeon's hand, providing reassurance that the tool was being held correctly.
As a result of this user-centered design approach and solid mechanical engineering, Baxano was able to release to market a flexible, user-friendly system for lumbar spinal decompression that reduces risk and recovery time for the patient. "This is the first disposable system for treating spinal stenosis," Wallace notes. "But more importantly, there's no product that goes out the foramen in this manner and allows you to get a full foraminal decompression without compromising the biomechanical integrity of the facet joint."