Future

BME
240

BASIS
Up to now it was not known whether motor and sensory pathways of missing or denervated limbs remain intact long periods of time after amputation. It has been examined and confirmed that both central and peripheral motor and somatosensory pathways retain significant residual connectivity and function long after amputation. This means that these residual nerves still work and that they can be used to interface with prosthetic limbs to achieve pseudo-naturalistic afferent feedback and efferent control. Such a device would far surpass current myoelectric and body-powered systems.

APPROACHES
To obtain a signal from a nerve the activity must be precisely recorded from individual nerves. One idea is to use Longitudinal Intrafascicular Electrodes (LIFEs), which provide an interface to microclusters of neurons with in severed fascicles of proximal nerve stumps allowing isolated investigation of the viability of motor and sensory neurons and their related central neural connections.

When recording a patient will make limb movements of the phantom limb, meaning they will pretend that their limb is still attached and functional. The signals produced are recorded by the electrodes and transmitted to the prosthetic device creating multiple simultaneous movements far surpassing the capabilities of myoelectric prosthetics.

Control is only part of the magic. The other part, which is most impressive is the ability to give sensory feedback from a prosthetic limb allowing further refinement of control and the naturalistic experience of using the device as if it was part of the patient’s body.

SET BACKS
Potential problems that are still being investigated and researched are the possibilities that no residual nerves exist in the region and that reorganization of CNS areas related to missing limb regions. Viability of the proximal nerve stump, up till recently posed a problem, but in September of 2003, researchers at the Rehabilitation Institute of Chicago (RIC) successfully completed the world’s first truly bionic arm for a man name Jesse Sullivan. Mr. Sullivan suffered a traumatic electrical power-line accident in which both of his arms suffered sever tissue damage requiring amputation of both at the shoulders. Due to the sever nerve damage suffered Mr. Sullivan had to have nerves taken from his arms and transplanted into his pectoral muscles where they were interfaced to a mechanical arm.
Since the initial success of the procedure the researchers at the RIC have further refined Mr. Sullivan’s prosthesis. Now his prosthesis has six motors to move the device's shoulder, elbow and hand in unison. Thanks to hand sensors, Mr. Sullivan can even gauge pressure and fine-tune his grip.