Mechanical efficiency during gait of adults with transtibial amputation: a pilot study comparing the SACH, Seattle, and Golden-Ankle prosthetic feet.

As more and more prosthetic feet become commercially available, the selection of the appropriate device is a more difficult task for clinical team members. To date, ranking prosthetic feet based on biomechanical parameters has been done using the spring efficiency. The current analytical technique for calculating spring efficiency has two flaws: first, prosthetic feet with a bendable flexible keel are analyzed the same way as those with an articulated ankle and a rigid foot, and second, there is no accounting for the energy losses in the viscoelastic cosmetic material surrounding the keel. This paper develops a rigorous technique to calculate the net energy stored or dissipated and then recovered during the stance phase of gait. Five adults with transtibial amputation were tested with three different prosthetic feet: SACH, Seattle, and Golden-Ankle. The subjects walked at self-selected cadence and stepped on a force plate while two-dimensional segmental kinematic and kinetic data were collected. The results showed that the Golden-Ankle stored or dissipated and then recovered significantly more energy than either the SACH or Seattle. The time to reach foot flat was also significantly reduced for the Golden-Ankle in comparison to both the others. Because the cosmetic material of the SACH foot can store or dissipate and then recover as much energy as the Seattle foot, the SACH foot should be considered an energy-storing foot. Finally, the net efficiency alone can not discriminate adequately among different types of prosthetic feet; therefore, one should consider the time to reach foot flat and the amount of energy recovered as additional objective criteria (weight, maintenance, and cosmesis) for selection of a prosthetic foot device.