Biomechanical effect between conventional and 3-dimensional printed customized foot orthoses on medial longitudinal arch support and rearfoot angle in adults with flexible flatfeet

Background: Customized foot orthoses are used to treat flexible flatfoot regarding medial longitudinal arch (MLA) support, alignment correction, and pain management. Recently, 3-dimensional (3D) printing orthosis has become the focus of discussion regarding function and manufacturing. We aimed to investigate differences in biomechanical effects between flat insole (Flat), conventional foot orthosis (Cinsole), and 3D printed foot orthosis (3Dinsole) use on MLA support and rearfoot alignment during walking in adult flexible flatfeet. Methods: Twelve men with flexible flatfoot were recruited. Data were collected and analyzed using a Vicon motion capture system under 3 trial conditions: Flat and >1 month after using Cinsole and 3Dinsole. Repeated-measures analysis of variance with Bonferroni post hoc tests was used to compare kinematics variables, foot pain, and satisfaction. Result: Dynamic navicular drop significantly reduced with the use of the Cinsole and 3Dinsole compared with Flat ( P < 0.001; ηp 2 = 0.65). The maximum rearfoot eversion angle with the use of the Cinsole and 3Dinsole significantly reduced from Flat ( P < 0.001; ηp 2 = 0.56). Foot pain score significantly decreased after using foot orthoses; satisfaction between Cinsole and 3Dinsole was not significantly different. Conclusions: Thus, Cinsole and 3Dinsole are effective alternative treatments of MLA support and rearfoot alignment in adults with flexible flatfoot. 3D printing is a future technology with potential to replace conventional production methods. However, material characteristics, design, and manufacturing process can affect treatment outcomes; hence, our results may not represent all variations of 3D printed foot orthoses.