XWH - 09 - 2 - 0067 TITLE : Determining the Marker Configuration and Modeling Technique to Optimize the Biomechanical Analysis of Running - Specific Prostheses

Body segment inertial properties (mass, center of mass position, and moment of inertia)affect the joint kinetics and subsequent limb control during ambulation. Accurate segmentinertial property estimations are necessary for properly calculating kinetic parameters andappropriately interpreting these data. Limited information currently exists related to inertialproperties of various running-specific prosthetic designs which limits the joint kineticinformation that can be generated and interpreted during running analyses. The purpose of thisstudy was to determine the inertial properties for four of the most common running-specificprostheses currently available on the market across three stiffness categories for each model. Apredictive equation was developed to estimate the center of mass (COM) positions of the variousprosthetic designs, and a trifilar pendulum is described for measuring the prostheses moments ofinertia. The predictive equation matched the measured COM exactly when prosthesis-specificinputs were used and produced errors between 0.1-2.8 cm when using average input valuesacross prostheses for a specific design. The trifilar pendulum estimated inertial properties within-6.21 x10 kg·m2 (≤ 1%) of a block with known inertia. Misalignments of the block’s COM withthe pendulum’s center of rotation ≤ 5cm yielded errors ≤ 0.0027 kg·m. Inertial properties aboutany axis varied ≤ 0.0038 kg·m within the tested prosthetic designs due to different stiffnesscategories, although inertial properties differed more substantially between different designs.Inertial estimation errors from pendulum measurements were less than or equal to errors associated with various methods for predicting intact limb inertial properties indicating that the