A unified deformable (UD) segment model for quantifying total power of anatomical and prosthetic below-knee structures during stance in gait

Anatomically-relevant (AR) biomechanical models are traditionally used to quantify joint powers and segmental energies of lower extremity structures during gait. While AR models contain a series of rigid body segments linked together via mechanical joints, prosthetic below-knee structures are often deformable objects without a definable ankle joint. Consequently, the application of AR models for the study of prosthetic limbs has been problematic. The purpose of this study was to develop and validate a unified deformable (UD) segment model for quantifying the total power of below-knee structures. Estimates of total below-knee power derived via the UD segment model were compared to those derived via an AR model during stance in gait of eleven healthy subjects. The UD segment model achieved similar results to the AR model. Differences in peak power, total positive work, and total negative work were 1.91 +/- 0.31%, 3.97 +/- 0.49%, and 1.39 +/- 0.33%, relative to the AR model estimates. The main advantage of the UD segment model is that it does not require the definition of an ankle joint or foot structures. Therefore, this technique may be valuable for facilitating direct comparisons between anatomical and disparate prosthetic below-knee structures in future studies. (C) 2012 Elsevier Ltd. All rights reserved.