Inflatable spine implants could treat severe pain

Engineers have developed an ultra-thin inflatable spine implant that could treat severe pain without the need for invasive surgery.

The device, developed by University of Cambridge researchers, combines soft robotic techniques with ultra-thin electronics and microfluidics.

"Spinal cord stimulation (SCS) is a treatment of last resort, for those whose pain has become so severe that it prevents them from carrying out everyday activities," said Dr Damiano Barone from Cambridge's Department of Clinical Neurosciences, one of the paper's senior authors. "However, the two main types of SCS devices both have flaws, which may be one reason their use is limited, even though millions struggle with chronic pain every day."

The new device is as thin as a human hair, so it can be rolled into a cylinder, inserted into a needle, and implanted into the epidural space of the spinal column – the same place where painkilling injections are administered during childbirth.

Once it’s been positioned correctly, the device is inflated with water or air and unrolls like a tiny air mattress to cover a section of the spinal cord. Then it can be connected to a pulse generator, and the ultra-thin electrodes in the device begin sending small electrical currents to the spinal cord to disrupt pain signals.

Early tests suggest this could be an effective form of treatment for severe pain which is unresponsive to painkillers – and that it could be adapted to treat paralysis or Parkinson’s disease. Similar technologies currently exist for spinal cord stimulation, but they’re bulky and require invasive surgery, while keyhole devices aren’t as effective. 

"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 Dr Christopher Proctor from Cambridge's Department of Engineering, the paper's other senior author. "This could help bring this life-changing treatment option to many more people."

A combination of manufacturing techniques were used for the finished device, which is just 60 microns thick: flexible electronics, tiny microfluidic channels, shape changing materials. "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.

"Our earlier versions were actually so thin that they were invisible to x-rays, which the surgeon would need to use to confirm they're in the right place before inflating the device," said co-first author Ben Woodington, also from the Department of Engineering. "We added some bismuth particles to make it visible without increasing the thickness too much. Designing a device is one thing, but putting it into surgical use is quite another."

The device has been tested in a human cadaver, and researchers are now working to manufacture the device in the hope of beginning tests in two or three years. "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 Barone. "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."

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