Development of a validated musculoskeletal model of the thumb to investigate the impact of anatomical features on joint function.

The thumb is a key factor in normal hand function, and full thumb mobility is essential to perform simple tasks of daily living, such as drinking coffee or buttoning a shirt. However, in patients who suffer from osteoarthritis (OA) of the thumb base, these activities are impaired because of pain and restricted mobility of the thumb. In half of the patients with thumb base OA, both the trapeziometacarpal (TMC) joint and the more proximal scaphotrapeziotrapezoidal (STT) joint are affected. Osteoarthritis is a joint disorder characterized by degradation of the articular cartilage and radiographic abnormalities. A recent study showed that changes in bone geometry are already present in early stages of thumb base OA. Ligament laxity and degeneration are also often associated with the disease, resulting in decreased joint stability. How these specific morphological changes affect the biomechanics of the thumb base joint remains, however, unclear. To address this, I propose to use a modelling approach. One of the strengths of computational modelling is that it enables obtaining data that are difficult or impossible to measure experimentally. Moreover, it allows investigating how the movement or loading are affected by changes in a specific property of the model (for example muscle property). The general hypothesis of this project is that changes in 3D geometry of the TMC joint or in the surrounding soft-tissue properties will lead to alterations in joint biomechanics. The aim of this project is to develop and validate a musculoskeletal model of the thumb that will allow us to investigate the impact of specific changes in bone geometry and surrounding soft-tissue on the joint biomechanics, and study the interaction between morphology, joint kinematics and joint loading. Additionally, I will evaluate the use of the developed thumb model in a clinical context (for example, investigate how joint loading and kinematics are affected by morphological changes due to OA).