Surgeons first rewired nerve endings in the patient’s stump to place them close to the skin surface. Six sensors were fitted to the base of the foot, to measure the pressure of heel, toe and foot movement.
These signals were relayed to a micro-controller which relayed them to stimulators inside the shaft where it touched the base of the stump. These vibrated, stimulating the nerve endings under the skin, which relayed the signals to the brain.
Prof Egger said: “The sensors tell the brain there is a foot and the wearer has the impression that it rolls off the ground when he walks.”
Wolfgang Ranger, a former teacher, who lost his leg after a blood clot caused by a stroke, has been testing the device for six months, both in the lab and at home.
He said: “I no longer slip on ice and I can tell whether I walk on gravel, concrete, grass or sand. I can even feel small stones.”
The 54-year-old also runs, cycles and goes climbing.
Another major benefit was a reduction in excruciating “phantom limb” pain felt by Mr Rangger for years following the amputation.
