Osteotomy simulation for normal gait recovery of flexible flatfoot patients and comparison of kinematics by osteotomy techniques

Abstract

Flexible flatfoot is a type of flatfoot that medial longitudinal arch of the foot collapses, and it has a flattened medial arch and valgus heel only in weight-bearing position. As the Achilles tendon attached to the calcaneus gets misaligned by the hindfoot valgus, the force to lift the hindfoot is transmitted inefficiently, causing abnormal gait. Since the structure of flexible flatfoot is deformed, the posterior tibialis muscles and medial ligaments of the foot, which play a role in maintaining the medial arch of the foot, are weakened which causes degeneration and pain of the ligaments. The hindfoot valgus of the flexible flatfoot patients causes osteoarthritis of the lateral side of the talar cartilage and the impingement of the talus and fibula. They cause pain in the lateral side of the tibiotalar joint. In order to return the patient’s foot to normal, calcaneal lengthening and medial displacement calcaneal osteotomy are widely used. However, there is no quantification about the effect of the two surgeries on reducing the lateral pain. To examine the musculoskeletal characteristics of flexible flatfoot patients and the effect of each surgery on patients, researches using optical marker based motion capture system and cadaveric studies have been conducted. Meanwhile, analyzing in vivo dynamics during walking is still difficult problem. Recently, foot models using musculoskeletal inverse dynamics simulation have been developed. However, a foot model that reflects the physical characteristics of flexible flatfoot patients has not been developed yet. This study aims to confirm the difference in the kinematics and kinetics between the normal foot and flexible flatfoot through musculoskeletal inverse dynamics simulation by developing a foot model reflecting the physical characteristics of patients with flexible flatfoot. In addition, by performing virtual surgeries, calcaneal lengthening and medial displacement calcaneal osteotomy, to the foot model, we analyzed the effect of each operation on the dynamics of the body to help select surgery that reduces contact forces on the tibiotalar joint so that thought to reduce the pain on the joint.