Experimental assessment of the influence of custom 3D Printed insoles on the gait of healthy subjects

Additive manufacturing enables personalized foot orthoses with subject-specific geometry and controllable mechanical properties. Evidence on how short-term acclimatization influences gait biomechanics with 3D-printed insoles remains limited, with many studies focusing on immediate responses or longer-term habituation. This thesis investigated the effects of custom 3D-printed thermoplastic polyurethane (TPU) insoles on gait biomechanics in ten healthy adults, comparing immediate use with a two-hour continuous-wear acclimatization period. Insoles were designed from subject-specific geometry and fabricated using fused deposition modeling. Three-dimensional marker trajectories and ground reaction forces were acquired using a stereophotogrammetry system synchronized with a force platform. Joint kinematics and external joint kinetics were computed using a CAST-based model and Grood and Suntay joint coordinate conventions. Participants completed four sequential conditions: factory insole (Normal), no insole (Without), custom insole worn immediately (Withinsole), and the same insole after two hours of continuous wear (Withinsole2). Condition effects were assessed using within-subject statistical comparisons with post-hoc correction. Relative to other conditions, Without showed increased pelvis tilt and increased knee internal rotation. Both 3D-printed conditions were associated with increased stride length compared with Normal. Compared with immediate use, Withinsole2 showed reduced knee internal rotation and increased peak ankle power generation (including higher peak ankle power than Normal). These findings indicate that custom 3D-printed insoles can modify lower-limb gait kinematics and kinetics and that a short acclimatization period can affect the observed biomechanical response.