Wilmington Robotic EXoskeleton (WREX)

Investigators:

• Tariq Rahman, PhD
• Michael A. Alexander, MD
• William G. Mackenzie, MD
• Whitney Sample, BFA
• Shanmuga S. Jayakumar, MD

Children with neuromuscular disease often have difficulty moving their arms and performing activities of daily living due to muscle weakness. This project addresses these concerns with the development of WREX, an arm orthosis that helps children with very little residual strength to move their arms in space. WREX is primarily intended for people with muscular dystrophy, spinal muscular atrophy and arthrogryposis in which the distal muscles are less affected and sensation remains intact.

WREX is a modular body-powered orthosis that is mounted to a person’s wheelchair or to a body jacket. It is a two-segment, four-degrees-of-freedom exoskeletal arm, energized by elastic bands that aid in moving the arm in 3D space. The WREX allows full passive range of motion of the arm and provides a sense of flotation that assists in voluntary movement. It can easily be adjusted to accommodate subjects of different size, weight, and arm lengths by changing the number of bands or sliding the telescoping links. WREX is typically mounted to a wheelchair. It is also being used for children with arthrogryposis who can walk independently by attaching the WREX to a body jacket. WREX was conceived and developed at the Alfred I. duPont Hospital for Children and is being sold by JAECO Orthopedics. It can also be found in the Sammons Preston catalogue.

WREX Videos

Video 1

Video 2

The next generation of WREX currently under development the “WREX II” has easily adjustable link lengths and anti-gravity lift. It can also be switched from the right to the left hand and is enclosed in a plastic cover. WREX II is motorized so a user can lift heavier objects and overcome profound weakness. The motors assist the rubber bands in creating just the right tension to lift the arm.

References

Rahman T, Sample W, Jayakumar S, King MM, Wee JY, Rahamim S, Alexander M, Scavina M, Clark A. “Passive exoskeletons for assisting limb movement”. J Rehab Res Develop 2006;43:1-7

Sanchez RJ, Liu J, Rao S, Shah P, Smith R, Rahman T, Cramer SC, Bobrow JE, Reinkensmeyer DJ "Automating Arm Movement Training Following Severe Stroke: Functional Exercises with Quantitative Feedback in a Gravity-Reduced Environment" Transactions of the IEEE on Neural Systems and Rehabilitation Engineering:14(3):September 2006: 378-389

Rahman T, Sample W, Seliktar R. Design and testing of WREX. In: Bien ZZ, Stefanov D, eds. Advances in Rehabilitation Robotics. Springer-Verlag, Berlin. 2004;243-250.

Rahman T., Ramanathan R., Seliktar R., Harwin W., "A Simple Technique to Passively Gravity-Balance Articulated Mechanisms" Trans. of the ASME- J of Mechanical Design, Vol. 117, No 4, pp. 655-658, December 1995