Dr Susan MacKinnon is the first surgeon in the world to carry out nerve transplants. Her pioneering work in St Louis, Missouri, utilising nerves from dead bodies, is the only hope for patients who would otherwise face lifelong paralysis in a limb. It's thanks to her, for instance, that three-year-old Rebecca, whose hand was almost completely paralysed after a garden accident, can play like othertoddlers. In tonight's film QED's cameras show Dr MacKinnon performing only the sixth operation of its kind on a teenager who severed an arm in a water sports accident.