Restoration of hand and arm function to people with tetraplegia as a result of damage to the spinal cord in the neck through the use of functional electrical stimulation (FES).

Abstract

Functional Electrical Stimulation (FES) therapy is a widely used rehabilitation technique to improve the hand functions of people with spinal cord injuries (SCI) and stroke. Two of the upper limb FES devices – the NeuroControl® Freehand System and the NESS H200 have received FDA approval and have been successfully commercialised. At the time of writing, out of the two devices, only NESS H200 was commercially available but the use of rigid arm splint limited the number of people who could functionally use the device. A new four channel upper limb FES device called the TetraGrip was developed during this research work. This device was controlled using an IMU based shoulder position sensor strapped across the contralateral shoulder and did not use a rigid arm splint. This allowed flexibility in electrode position and more people were able to use the system. The device was programmed to perform two hand movements – the key grip and the palmar grasp. Besides these functional modes, it was programmed to generate an exercise sequence that alternated between the palmar grasp and key grip movements. The device was tested on fourteen able bodied volunteers who used the shoulder position sensor to operate the device. This study was helpful in establishing the repeatability and reproducibility of the device and also helped in improving the device based on the feedback from users. This study also helped in exploring the possible combination of electrode positions for achieving functional movements. It was then clinically tested on two people with C6 tetraplegia who participated in a twelve week long study. The volunteers used an Odstock® Microstim to exercise the desired muscles for four weeks and then came back to the clinic once a week for eight weeks to use the TetraGrip. They were assessed using outcome measures such as the grip strength test, the box and block test and the grasp release test. As the study progressed, both the volunteers showed improvements in their ability to perform the specified tasks using key grip and palmar grasp movements and on the last day of the study, they were able to perform activities of daily living using the TetraGrip such as holding a pen and writing and holding a fork and eating lunch.