Research Article Biomechanical Evaluation and Strength Test of 3D-Printed Foot Orthoses Kuang-Wei Lin , 1 Chia-Jung Hu, 1 Wen-Wen Yang, 2 Li-Wei Chou , 1 Shun-Hwa Wei, 1 Chen-Sheng Chen , 1 and Pi-Chang Sun 3,4 1 Department of Physical Therapy and Assistive Technology, National Yang-Ming University, Taipei, Taiwan 2 Department of Sports Medicine, China Medical University, Taichung, Taiwan 3 Department of Rehabilitation Medicine, Taipei City Hospital, Taipei, Taiwan 4 Faculty of Medicine, National Yang-Ming University, Taipei, Taiwan Correspondence should be addressed to Li-Wei Chou; lwchou@ym.edu.tw and Chen-Sheng Chen; cschen@ym.edu.tw Received 28 March 2019; Revised 20 September 2019; Accepted 21 November 2019; Published 7 December 2019 Academic Editor: Fong-Chin Su Copyright © 2019 Kuang-Wei Lin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Foot orthoses (FOs) are commonly used as interventions for individuals with flatfoot. Advances in technologies such as three-dimensional (3D) scanning and 3D printing have facilitated the fabrication of custom FOs. However, few studies have been conducted on the mechanical properties and biomechanical effects of 3D-printed FOs. The purposes of this study were to evaluate the mechanical properties of 3D-printed FOs and determine their biomechanical effects in individuals with flexible flatfoot. During mechanical testing, a total of 18 FO samples with three orientations (0 ° , 45 ° , and 90 ° ) were fabricated and tested. The maximum compressive load and stiffness were calculated. During a motion capture experiment, 12 individuals with flatfoot were enrolled, and the 3D-printed FOs were used as interventions. Kinematic and kinetic data were collected during walking by using an optical motion capture system. A one-way analysis of variance was performed to compare the mechanical parameters among the three build orientations. A paired t -test was conducted to compare the biomechanical variables under two conditions: walking in standard shoes (Shoe) and walking in shoes embedded with FOs (Shoe+FO). The results indicated that the 45 ° build orientation produced the strongest FOs. In addition, the maximum ankle evertor and external rotator moments under the Shoe+FO condition were significantly reduced by 35% and 16%, respectively, but the maximum ankle plantar flexor moments increased by 3%, compared with the Shoe condition. No significant difference in ground reaction force was observed between the two conditions. This study demonstrated that 3D-printed FOs could alter the ankle joint moments during gait. 1. Introduction Foot orthoses (FOs) are commonly used as interventions for individuals with flexible flatfoot [1, 2]. Wearing FOs might improve the pain scores [3] and alter the kinematics and kinetics of the rearfoot; for example, FOs reduce the peak rearfoot eversion [3, 4] and joint moment in the frontal plane [5]. However, a study indicated that the same shoe insert interventions produce substantially different effects for dis- similar individuals [6]. The actual prescription of orthotic devices is patient specific; this is because various levels of malalignments likely require different FO designs. According to the current manufacturing method, FOs can be either custom fabricated or prefabricated. Although prefabricated FOs are less expensive and are readily available as off-the- shelf products, custom FOs normally exhibit a better fit to an individual’s foot and are more effective than prefab- ricated FOs [7]. Custom FOs can be prescribed in three types: soft, semirigid, and rigid. The traditional plaster-molding and vacuum-forming processes are used for fabricating rigid or semirigid FOs. For fabricating a conventional rigid FO, the foot is pressed into a foam box to create a negative impres- sion of the plantar surface. The negative impression is used as a mold for plaster to produce the positive foot model. The positive model is draped with heated shell material and molded around the model using a vacuum press. The extra material around the edges is trimmed to complete the FO. Hindawi Applied Bionics and Biomechanics Volume 2019, Article ID 4989534, 8 pages https://doi.org/10.1155/2019/4989534