Arthrorisis of the subastragalus joint represents one of the surgical treatments for addressing flexible flatfoot, a condition caused by joint deformity. The device is designed to restore the correct joint relationships between the astragalus and calcaneus, with the goal of maintaining the new and proper joint alignment over time, typically allowing for bone remodeling along natural growth lines, usually within a few years. Several implants and various variations of the procedure have been developed.There are currently no prospective studies that assess radiographic and clinical data over time. Therefore, the purpose of this study is to prospectively analyze the outcomes of surgical intervention using subastragalus arthrorisis with a polymeric endorthesis for the treatment of flexible flatfoot during the growth period in a consecutive series of 55 patients.