OUT ON A LIMB: IMPLANTABLE ELECTRODES CREATE INTUITIVE PROSTHETIC MOVEMENT

Macquarie University Hospital surgeons are integrating an innovative neuro-machine interface into existing bionic limb replacement, ushering in the next generation of neuro-prosthetics.


Advances in prosthetic development over recent decades have focused on optimising the interface between the artificial limb and a patient’s body ¬– not only attaching the new limb but also enhancing information transfer.

Macquarie University Hospital orthopaedic surgeons have now combined several surgical procedures that together form a pioneering new approach to information transfer to bionic limbs for upper-limb amputees.

“At Macquarie University Hospital, we are taking existing targeted muscle integration and osseointegration techniques and adding implantable electrodes,” explained Associate Professor Munjed Al Muderis, one of Australia’s leading hip and knee surgeons and an osseointegration specialist.

“It is the combination of the three procedures that makes the interface more intuitive than ever before. The key to this advance has been implantable electrodes that can now capture complex brain signals to enable more natural upper limb mobility.

“So, in practice, when the patient thinks about moving his or her finger, the finger moves; when thinking of moving the wrist, the wrist moves.”

Targeted muscle reinnervation (TMR) was developed in the US several years ago. It allows surgeons to transfers residual nerves to alternative muscle sites. After surgery, the target muscles produce electromyogram (EMG) signals that serve as amplifiers of motor commands from the transferred arm nerves for control of the elbow, wrist and hand. Osseointegration provides a bone-anchored method for TMR.

Now, implantable myoelectrodes transmit and receive computer-generated electrical signals to and from the brain. Because multiple signals can now be captured, a more natural response is possible.

“Electrodes have long been used for other medical devices: pacemakers, most commonly,” said Associate Professor Al Muderis. “What we have done is to modify these for our purposes.

“It is the sophisticated information feedback enabled by the implantable myoelectrode that enables intuitive control. This stands to transform neuroprosthetics – and the lives of upper-limb amputees.

“What sounds like science fiction is a reality – controlling a limb with the mind. With the Osseointegration Clinic at Macquarie University Hospital now well established, we are looking ahead to making this new development part of a permanent clinical program.

“It’s still so new we are developing it as we go – optimising the surgical approach and capturing patient outcomes. The long-term goal is to make it clinically available to large patient populations, with the real benefit for the next generation of people who have lost upper limbs from injury or cancer.”