Joint venture

Inside a bright, freshly remodeled basement lab at Dartmouth College's Thayer School of Engineering, John Collier slides a small white rectangle of polyethylene plastic toward me. He and I, along with his colleague Michael Mayor, are sitting at a large oak table covered with failed orthopedic implants - shiny cobalt balls and white plastic sockets, titanium stems once thrust into femurs to hold artificial hips in place. Over the last three decades, Collier, an engineer, and Mayor, a surgeon, have collected and tested nearly 9,000 artificial joints to determine how and why they failed. No lab has room for all those parts, so the vast majority of the implant collection is stored off campus in a rented warehouse.