Effect of therapeutic insoles on the medial longitudinal arch in patients with flatfoot deformity: A three-dimensional loading computed tomography study

- We investigated the effect of therapeutic insoles in patients with mild flatfoot.
- We examined tarsal bone rotational angles with accessory and therapeutic insoles.
- CT scans were performed on both feet under unloaded and full-body-loaded conditions.
- The CT scans were performed with accessory insoles and with therapeutic insoles.
- The therapeutic insoles suppressed the eversion of the talocalcaneal joint.

BackgroundInsoles are frequently used in orthotic therapy as the standard conservative treatment for symptomatic flatfoot deformity to rebuild the arch and stabilize the foot. However, the effectiveness of therapeutic insoles remains unclear. In this study, we assessed the effectiveness of therapeutic insoles for flatfoot deformity using subject-based three-dimensional (3D) computed tomography (CT) models by evaluating the load responses of the bones in the medial longitudinal arch in vivo in 3D.MethodsWe studied eight individuals (16 feet) with mild flatfoot deformity. CT scans were performed on both feet under non-loaded and full-body-loaded conditions, first with accessory insoles and then with therapeutic insoles under the same conditions. Three-dimensional CT models were constructed for the tibia and the tarsal and metatarsal bones of the medial longitudinal arch (i.e., first metatarsal bone, cuneiforms, navicular, talus, and calcaneus). The rotational angles between the tarsal bones were calculated under loading with accessory insoles or therapeutic insoles and compared.FindingsCompared with the accessory insoles, the therapeutic insoles significantly suppressed the eversion of the talocalcaneal joint.InterpretationThis is the first study to precisely verify the usefulness of therapeutic insoles (arch support and inner wedges) in vivo.