He is part of a small group of American physicians testing the effectiveness of the device which has been used in Europe for about 10 years with excellent results. The device consists of two specially formed metal pieces, one fitting snugly into the leg bone and the other into the ankle bone, with a molded plastic plate in between that allows movement. It removes constraint and allows movement. When there's constraint, the pieces eventually loosen with wear, and the joint fails. This prosthetic ankle could be a viable alternative for people with osteoarthritis who before had to either live with the pain or undergo surgery to fuse the ankle bones together.
Fusion cures the pain but leaves the foot solidly set in one position, which affects gait.
Normally, the ankle flexes about 60 degrees. The prosthesis gives patients about 30-degree flexion in the foot whereas with fusion, they get zero. Fusion also increases stress on surrounding joints, which must now compensate for the immovable foot. That increases the chance those joints will become arthritic. Someone who has undergone ankle fusion can walk, but couldn't run or jog.