Effect of Ankle-foot Orthoses Trim Line Modifications on Ankle and Knee Motion and Force.

The purpose of this study is to quantify changes in ankle and knee motion and force resulting from five progressive modifications to the anterior-posterior trim lines of thermoformed ankle-foot orthoses (AFO). It is hypothesized that the AFO with the most anterior trim line will prevent the most plantar flexion during loading response (the first 10% of the gait cycle)and prevent the most dorsiflexion at terminal stance (from 30 to 50% of the gait cycle) as compared to the non-device condition. This will be evidenced by the sagittal plane ankle motion and ground reaction force magnitude and location during loading response and terminal stance. Additionally, the angular velocity of knee flexion will increase during these same periods. By contrast, as the trim lines are moved more posterior this will result in lowering the effective stiffness of the device which will result in progressive increases in dorsiflexion and allow increasing amounts of knee flexion during terminal stance.