Raising a spoon to eat, using a toothbrush, lifting a hairbrush, raising a hand in class: activities that most of us take for granted can present a difficult challenge for children and adults with arm muscle weakness.
The Wilmington Robotic Exoskeleton (WREX), designed and developed by the Pediatric Engineering Research Laboratory (PERL) in the Center for Orthopedics Research and Development (CORD), Nemours/Alfred I. duPont Hospital for Children, Wilmington, Delaware, allows patients with upper-limb weakness to perform activities of daily living (ADLs), explains Tariq Rahman, PhD, CORD director.
The device benefits patients with neuromuscular conditions including spinal muscular atrophy (SMA), arthrogryposis, stroke, cerebral palsy, and muscular dystrophy. “To date we have seen the most benefit for children with spinal muscular atrophy, as the condition remains fairly non-progressive,” Rahman says. One SMA patient has used the WREX on a daily basis for about six years and now attends Lehigh University, Bethlehem, Pennsylvania. “It is an indispensable part of his life,” Rahman says.
With two links and four degrees of freedom, the WREX approximates human anatomy and uses the energy of optimally placed elastic bands to negate the effects of gravity on arm movements. The device can be attached to the back of a wheelchair or to a back brace for ambulatory users.
The WREX allows full three-dimensional movement, unlike the balanced forearm orthosis (BFO), also called the ball bearing feeder, which had been the standard functional orthosis. Also unlike the BFO, the WREX lies alongside the arm and so does not interfere with doorways and wheelchair armrests, Rahman notes.
Motorized Hybrid Coming
A motorized design, WREX II, is being developed to provide a power assist when more strength is needed. “However, it is being designed as a hybrid of rubber bands and motors to keep it smaller and less expensive,” Rahman explains. Users will control it by applying a small force in the direction they want to move their hands. This force will be sensed by a force sensor, which in turn will signal the motors to move in a certain direction. An analogy would be power steering in a car where human effort is amplified.” He adds, “This technology is similar to that being developed for exoskeletons for soldiers in the battlefield.”
Established in 1936 by philanthropist Alfred I. duPont, Nemours currently supports a number of children’s healthcare facilities in Delaware, Pennsylvania, New Jersey, and Florida (For more information, visit www.nemours.org). Visit YouTube to watch the WREX in action.
