A non-biomimetic approach for producing shank kinematics and energetics during the stance phase of gait

Stanhope, Steven J.Individuals with transtibial amputation depend on prosthetic ankle-feet to ambulate. However, even today's state-of-the-art energy-storing-and-returning and bionic ankle-feet fail to replicate all the functions of the natural system. This deficiency may be due in part to the difficulty in analyzing prosthetic systems using traditional methods. Roll-over shape, the geometry the ankle-foot deforms to during stance, has been proposed as an improved characterization method. While useful, roll-over shape does not account for the period of late stance, during which important propulsive functions occur. Shank progression - the kinematics (translation and rotation) and energetics (flow of segmental power) of the lower leg - may provide a more complete description of ankle-foot function, including push-off. The overall purpose of the present study was to fully characterize the kinematics and energetics of shank progression during the stance phase of typical gait and to develop and evaluate alternate means of reproducing natural shank progression. Analyses were performed on an existing database of ten adult participants who completed overground instrumented gait analysis at a normal walking velocity. Shank kinematics were characterized by rotation and translation about an apparent virtual fixed ankle position. Power entered and exited the shank via the distal and proximal joint force terms, respectively. These data provided evidence for the design of a novel, non-biomimetic prosthetic shank capable of replicating shank kinematics and energetics via a "telescoping" (elongating) inverted pendulum mechanism. Such a device could lead to improved functional outcomes for prosthetic users in the future.M.S.University of Delaware, Biomechanics and Movement Science Progra