All Things D writes, I’m not usually a sucker for the warm and uplifting. But I’ll admit it: A recent viral YouTube video featuring a child’s inspiring story has got me all choked up. Two-year-old Emma Lavelle was born with arthrogryposis multiplex congenita (or AMC), a condition that stunts the development of her muscles and stiffens her joints. As a result, her capacity for movement has been severely limited, and she has spent much of her life undergoing surgeries and corrective treatments. One of the most promising treatments for those with AMC is the WREX device, a type of body cast that aids...