New spinal implant will help people with paraplegia

Microchip muscle implant developed at UCL stimulates more muscle groups than is currently possible with existing technology

Engineers have developed a microchip muscle stimulator implant that will enable people with paraplegia to exercise their leg muscles.

The project, carried out at University College London, represents the first time that researchers have developed a device of this kind that is small enough to be implanted into the spinal canal and incorporates the electrodes and muscle stimulator in one unit. The implant is the size of a child’s fingernail.

Although electrical stimulation of leg muscles has been used for some time, it is usually done by attaching electrodes to the outside of the legs and then connecting the electrodes to an external stimulator. This is too time-consuming to be used every day so few people with spinal cord injury continue with this method. 

At the moment electrical stimulation of nerve roots in the spinal canal can be carried out using implanted electrodes and an implanted stimulator connected by a cable. This latest research is the first to combine the electrodes and muscle stimulator in one unit so that more nerves can be stimulated and better function achieved.

The Engineering and Physical Sciences Research Council (EPSRC) project is being led by Professor Andreas Demosthenous from the department of electrical and electronics engineering at UCL. He said: “The work has the potential to stimulate more muscle groups than is currently possible with existing technology because a number of these devices can be implanted into the spinal canal. Stimulation of more muscle groups means users can perform enough movement to carry out controlled exercise such as cycling or rowing.”

The devices could also be used for a wide range of restorative functions such as stimulating bladder muscles to help overcome incontinence and stimulating nerves to improve bowel capacity and suppress spasms.   

The research team has overcome previous limitations by micro-packaging everything into one tiny unit. The latest laser processing technology has been used to cut tiny electrodes from platinum foil. These are then folded into a 3D shape (which looks like the pages of a book, earning the device the name of the Active Book). The pages close in around the nerve roots. They are micro-welded to a silicon chip which is hermetically sealed to protect against water penetration, which can lead to corrosion of the electronics.  

The Active Book will be made available for pilot studies sometime next year.