Analysis of residual limb changes using digital image correlation and finite element modeling

Local changes in the volume, shape, and mechanical properties of the residual limb can be caused by adjacent joint motion, muscle activation, hydration, atrophy, and more. These changes affect socket fit quality and might cause inefficient load distribution, discomfort, and dermatological problems. Analyzing these effects is an important step in considering their influence on socket fit, and in accounting for their contribution within the socket design process.

In this study, a 360° 3D digital image correlation (3D-DIC) system was developed for the full-field deformation measurements of the residuum. A multi-camera rig was designed for capturing synchronized image sets as well as force measurements from a hand-held indenter. Custom camera calibration and data-processing procedures were specifically designed to transform image data into 3D point clouds, and automatically merge data obtained from multiple views into continuous surfaces. Moreover, a specially developed data-analysis procedure was applied for correlating pairs of largely deformed images of speckled surfaces, from which displacements, deformation gradients, and strains were calculated. Characterization of the full-field deformations using 3D-DIC provides insight into the patterns and sources of the phenomena. 

In addition, local and subject-specific soft tissue mechanical properties were obtained by analyzing surface deformation and force measurement during indentation using inverse FE analysis. These data can be used to accurately describe the residuum’s biomechanical behavior. Consequently, prosthetic socket designs that take into account these effects can be considered.