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    How MIT brainpower returned a dancer to the stage

    MIT professor Hugh Herr designed the prosthetic ankle.
    Wendy Maeda/Globe Staff
    MIT professor Hugh Herr designed the prosthetic ankle.

    Adrianne Haslet-Davis can dance again because of a bionic ankle.

    Inside its casing is a sophisticated computerized machine filled with microprocessors and sensors that are smart enough to mimic the natural functions of muscle and tendon.

    The ankle in Haslet-Davis’s prosthetic was programmed in particular to respond to the many varied movements of dance. It stiffens up when the dancer needs a firmer stance or provides additional torque for forward thrust.


    The dancing ankle designed for Haslet-Davis, a professional dancer injured in the Boston Marathon bombings, is at the cutting-edge of prosthesis innovation — a huge leap forward in technology that may eventually be available for all amputees.

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    And not surprisingly, the ankle is the work of the bright minds at the Massachusetts Institute of Technology. A team at the MIT Media Lab led by professor Hugh Herr, himself a double amputee of the lower legs, spent the better part of a year designing the ankle.

    The team started with a customized version of a bionic ankle manufactured by BiOM, a robotics company in Bedford that Herr founded in 2007. The company’s ankles have been fit onto roughly 1,000 patients, about half of whom are veterans of the wars in Iraq and Afghanistan.

    Herr and his team studied dancers and in particular how their ankles responded to various movements, and then programmed those responses into the ankle designed for Haslet-Davis.

    On Friday, Herr explained that Haslet-Davis was an inspiration.


    “I really related to her passion for returning the dance floor,” said Herr, whose lower legs were amputated after a rock climbing accident in 1982. One of the motivations for his early work in prosthetics was getting back to his own passion at the time — climbing.

    The propulsion system in Haslet-Davis’s ankle is battery-powered and includes a motor and timing belt. Its spring is programmed so that it stiffens to absorb downward force and releases to provide propulsion.

    The ankle itself is designed and fitted based on the person’s ideal stride, which will help minimize abnormalities in gait that could lead to other health problems.

    The ankle is just the beginning for BiOM and its work in pushing the evolution of bionic prostheses, said Herr. Although he isn’t involved in the day-to-day running of the company, his vision for it extends far beyond the ankle.

    “We are basically building body parts from the ground up,” he said. “My business plan is to build one joint at a time.”

    Michael B. Farrell can be reached at Follow him on Twitter @GlobeMBFarrell.