Flat Feet

This study will examine how different short-term exercise and vibration conditions affect lower-limb muscle activity in young adults with flat feet and young adults with normal feet. Participants will complete several conditions, including whole-body vibration, whole-body vibration combined with plantar stimulation under different areas of the foot, and a Baduanjin heel-raise exercise. Surface electromyography sensors will be placed on the skin over selected lower-limb muscles to record muscle activity before and during each condition. Each participant will complete all study conditions in a balanced order. This study does not aim to treat flat feet or evaluate long-term clinical benefits. The purpose is to collect preliminary information on immediate muscle activation and foot discomfort, which may help design future studies on foot-related exercise, plantar stimulation, and rehabilitation training.

The goal of this observational study is to compare the use of a screw made of human bone (Shark-Screw®, Surgebright-GmbH) with the metal/Bio-Tenodesis screw (Arthrex) in the treatment of the symptomatic flatfoot using the medializing calcaneus osteotomy with flexor digitorum longus transfer (FDL) in adult patients. The advantage of the human bone screw is that after surgery no hardware removal is necessary. The screw is transformed from the body to normal bone. The main questions it aims to answer are: * Can the human bone screw achieve union rates like the metal/Bio-Tenodesis screw? * Is the time to union similar between the different screws? * Is the complication rate similar between the different screws? * Are the activity scores American Orthopaedic Foot and Ankle Society (AOFAS), Foot and Ankle Outcome Score (FAOS) and Foot Function Index (FFI) after surgery similar in the compared patient groups? Participants will have * the surgery * follow-ups at 6 weeks, 6 months, 1 and 2 years. * X-rays are performed at each follow up. * CT-scans are performed after 6 months. * activity scores are collected at the follow up after 6 months, 1 year and 2 years.

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.