32-3 Thursday, Jan. 5 14:00 - 14:15 Effects of decreased heel deflection on a passive walking prosthesis ISAACS, MR*; HENSEL, S; LEE, DV; Univ. of Nevada, Las Vegas; Technische Universität Darmstadt; Univ. of Nevada, Las Vegas firstname.lastname@example.org
This study explores the effect of heel deflection on whole body walking dynamics of persons with a unilateral transtibial amputation using a passive prosthetic, the Cheetah Xplore by Össur. After a baseline kinetic and kinematic data collection was completed, the user’s prosthesis was modified by the installation of a 4 mm wedge between the "heel" and the C-arm of the subject's device. This mechanical obstruction decreased the range of deflection of the carbon fiber components of the prosthesis during the heel strike of the step-to-step transition. The subject repeated the protocol with the modification and the mechanical cost of transport (CoTmech) for the two conditions was compared at different dimensionless velocities within the walking speed range. Slow, moderate, and fast walking speeds were prescribed to the participant for both the high and low deflection conditions to control for speed effects. The recorded data was utilized to determine the planar orientation of the force (F) and velocity (V) vectors of the CoM in every instance of the stride. A near perpendicular arrangement of F and V minimizes the CoTmech for steady speed walking. With this assumption in mind, the effectiveness of cooperating limbs is addressed with a novel assessment of the interlimb work done by the legs on the CoM during double stance. This type of analysis highlights potential deficiencies in the affected limb's step that are translated into the body dynamics and are quantifiable at the CoM level using the method we propose. The presentation will demonstrate the effectiveness of the new technique in whole body dynamics assessment, and will substantiate the importance of compliant mechanisms in prosthetic devices designed with the intention to restore human walking dynamics.