The Wilmington Robotic Exoskeleton (WREX) is an arm orthosis that helps children who have very little residual strength to move their arms in space. It is intended for those with muscular dystrophy, spinal muscular atrophy and arthrogryposis in which the distal muscles are less affected and sensation remains intact. Over time, the device has been made progressively smaller to fit patients as young as six years of age. However, when two-year old Emma Lavelle, suffering from arthrogryposis multiplex congenita, needed to be fitted with the WREX, its designers turned to 3D printing to create a smaller and more lightweight version than was possible with traditional tools.
The original WREX is made of hinged metal bars and resistance bands, and supports the arms allowing children to play, feed themselves and hug. The team that developed the WREX at Nemours/Alfred I. duPont Hospital for Children looked into ways to make the parts used in the exoskeleton both smaller and lighter, and ended up using a Stratasys 3D Printer to print a prototype WREX in ABS plastic. The resulting WREX was light enough to attach to a little plastic vest, which is now used by Emma every day.
A total of fifteen children so far have received a custom 3D-printed exoskeleton. In addition to being able to easily adapt the WREX to the necessary size, the design flexibility of 3D printing allows for continual improvements of the assistive device, working out ideas in CAD and building them the same day. The full story of Emma, who is happily using the exoskeleton that she now refers to it as her “magic arms”, is told in the video below:

More: Stratasys case study…; WREX project page…
(Hat tip: The Verge)