By Pat Anson, PNN Editor

A tiny inflatable device – about the width of a human hair – could make spinal cord stimulation less invasive and more practical for millions of people who suffer from chronic back or leg pain, according to researchers at the University of Cambridge.

Long considered the treatment of last resort, spinal cord stimulators (SCSs) are bulky devices implanted along the spine that use electrode wires connected to a battery to emit electric currents that block pain signals from reaching the brain. About 50,000 stimulators are surgically implanted every year, but many wind up being removed due to complications from surgery or because they are ineffective.

“Our goal was to make something that’s the best of both worlds – a device that’s clinically effective but that doesn’t require complex and risky surgery,” said Christopher Proctor, PhD, a research fellow at Cambridge’s Department of Engineering and one of the senior authors of a study published in Science Advances. “This could help bring this life-changing treatment option to many more people.”

Proctor and his colleagues developed a miniaturized electrode that is so small it can be rolled up into a tiny cylinder, inserted into a needle, and implanted into the epidural space of the spinal column.

As the video below shows, the device can then be inflated with water or air so that it unrolls like a tiny air mattress and covers part of the spine. When connected to a battery, the ultra-thin electrode can send small electric currents to the spinal cord, just like a traditional stimulator.

“In order to end up with something that can be implanted with a needle, we needed to make the device as thin as possible,” said co-author Ben Woodington, a PhD candidate in Cambridge’s Department of Engineering.

Researchers made the device with flexible electronics used in the semiconductor industry; tiny fluidic channels used in drug delivery; and shape-changing materials used in robotics.

“Thin-film electronics aren’t new, but incorporating fluid chambers is what makes our device unique – this allows it to be inflated into a paddle-type shape once it is inside the patient,” said Proctor.  

Early versions of the device were so thin they were invisible to x-rays, which surgeons would need to confirm the device was in the right place before inflating it. Researchers added some bismuth particles to make the device visible without increasing the thickness too much.

The experimental device has only been tested in human cadavers. More extensive testing and clinical trials will be required before the device can be used on patients – possibly in two or three years. The Cambridge research team is currently working with a manufacturer to further develop and improve the device.

“The way we make the device means that we can also incorporate additional components – we could add more electrodes or make it bigger in order to cover larger areas of the spine with increased accuracy,” said senior co-author Damiano Barone, MD, a clinical lecturer in Cambridge’s Department of Clinical Neurosciences.

“This adaptability could make our SCS device a potential treatment for paralysis following spinal cord injury or stroke or movement disorders such as Parkinson’s disease. An effective device that doesn’t require invasive surgery could bring relief to so many people.”

“This technology has the potential to transform clinical treatment, significantly improve pain management for so many people, and reach patients who cannot be treated with existing devices,” said Rachel Atfield, PhD, Commercialisation Manager at Cambridge Enterprise, which has patented the device.

A 2018 study by a team of investigative journalists found that spinal cord stimulators have some of the worst safety records of medical devices tracked by the U.S. Food and Drug Administration. A review of FDA data found over 500 deaths and 80,000 injuries involving stimulators since 2008. Patients reported being shocked or burned by the devices and many had them removed.