The Contribution of the Ligaments in Flatfoot Deformity, A Finite Element Study

Abstract

Progressive collapsing foot deformity (PCFD), initially known as adult acquired flatfoot deformity (AAFD), is a common degenerative disorder in which certain soft tissue stabilizers in the foot degenerate, resulting in ankle and foot pain. As the structures supporting the foot degenerate, a complex three‐dimensional deformity develops at multiple locations in the foot, including hindfoot valgus, midfoot planus (arch collapse), and forefoot abduction. Patients with longstanding PCFD often develop osteoarthritis of the midfoot or hindfoot joints leading to a fixed deformity and some even develop ankle arthritis. It was initially thought that dysfunction of the posterior tibial tendon (PTT) leads to the PCFD. However, later studies revealed that the degeneration of the arch and hindfoot supporting ligaments also plays a significant role. Despite the importance of ligaments in PCFD, the kinematic and kinetic effects of ligament degeneration and tears on each component of the deformity has not been well characterized. Moreover, the impact of individual ligament tears on changes in joint contact mechanics and the development of osteoarthritis has not been investigated. An improved understanding of the contribution of each of the ligaments to the deformity could be used to determine potential targets for early surgical interventions through ligament reconstruction that could prevent the progression of deformity and the development of arthrosis. Thus, the purpose of this Ph.D. study was to create and validate a computational model of the foot constructed from CT scan images in order to evaluate the impact of ligament failure on the development of PCFD and joint degeneration.