After Jennifer French, a young professional in consumer tech, fell down a ski slope and broke her spine in 1998, she couldn’t tell you what exactly happened next. The next few months passed in a blur; she hadn’t yet fully accepted her prognosis — paralysis for life — when she came across a clinical trial that promised to help her walk again.

In a surgery that lasted over seven and a half hours, researchers at Case Western Reserve University in Cleveland, Ohio, implanted electrodes in her muscles that would allow her to move her legs via an........

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