Conceptual Design of a Passive Arm Orthosis

For people suffering from neuromuscular diseases there is a need for a device to support the weight of their arm against gravity and allow either their residual muscle force or external power to position the arm in space. Many of the current assistive devices are externally powered, tend to be very bulky, and have poor aesthetics. The non-powered devices available suffer from limited range of motion and several other inconveniences. Home visits to patients suffering from SMA (spinal muscular atrophy) were made, and a literature search was performed to assess adequate design specifications, based mainly on range of motion, activities of daily living, and home environment. This paper presents a statically balanced, non-powered arm support design, which compensates the weight of the human arm against gravity in all of the four degrees of freedom of the human arm.