Image
Dressing, washing, feeding... Much more than a simple tool, the hand is the very symbol of autonomy in our daily activities. It is also a vector of communication and a precious gateway to the outside world.
Understanding and preventing rhizarthrosis
Wednesday, December 11, 2024
Dressing, washing, feeding... Much more than a simple tool, the hand is the very symbol of autonomy in our daily movements. It is also a vector of communication and a precious gateway to the outside world.
However, because of its intensive use, it is particularly vulnerable to pathologies such as osteoarthritis. For part of the population, rhizarthrosis - a form of osteoarthritis affecting the trapeziometacarpal (TMC) joint at the base of the thumb - hampers this vital grip, gradually limiting their autonomy and everyday comfort.
A widespread pathology, particularly among women, rhizarthrosis remains surrounded by many grey areas, with few preventive and rehabilitative solutions. Surgical interventions, while effective, are only considered in the advanced stages of osteoarthritis. Although the results are usually satisfactory, they do not fully restore grip functions.
Understanding and preventing rhizarthrosis is therefore a real challenge. To address these issues, an innovative project has been launched at the Institut des Sciences du Mouvement (ISM). Led by Laurent Vigouroux, Jean-Louis Milan and Benjamin Goislard de Monsabert, the project aims to develop a multi-scale model capable of better understanding the mechanisms underlying rhizarthrosis, and proposing concrete, personalized solutions.
A multi-scale model to better understand pressure distribution and triggering factors
For 15 years, Laurent Vigouroux has specialized in understanding how the hand works. When he joined the Institut des Sciences du Mouvement, he developed the subject into a genuine laboratory expertise, basing his work initially on musculoskeletal modeling, enabling the measurement of muscular efforts and the resulting forces on the joints.
This model has been used in a variety of applications, notably in a tennis elbow collaboration with Decathlon in which Benjamin Goislard de Monsabert was involved, but also in the field of climbing, which later gave rise to the SmartBoard start-up. Despite its ability to shed light on various pathologies, one of its limitations was encountered when it came to tackling the subject of osteoarthritis, requiring more precise geometric modeling of bone morphology to estimate the distribution of joint forces and contact pressures experienced by the cartilage.
Benjamin Goislard de Monsabert, then Jean-Louis Milan, joined the project to address this issue, integrating finite elements into the musculoskeletal model, enabling certain parameters to be modified at will and their criticality to be assessed. Based on a biomechanical analysis of a subject's gripping gesture, the musculoskeletal model is used to estimate the muscular forces generated by the subject. These muscular forces are then implemented in the finite element model of the hand, which takes into account the bony morphology of the fingers and the material properties of the bones, cartilage and ligaments. The finite element model then provides quantitative values of joint contact pressures and their location.
This multi-scale biomechanical modeling approach thus provides access to crucial information that is both anatomically accurate and faithful to muscular efforts. This information provides answers to unanswered questions, in particular concerning the triggers of rhizarthrosis:
Types of gripping: pinch gripping, or gripping between the index finger and thumb, places heavy demands on the joints, generating high contact forces. This technique is commonly used for high-precision tasks and is indispensable in many professions, such as dentistry or dressmaking, exposing these professionals to the problems associated with rhizarthrosis.
Bone morphology: more curved structures in the trapezium and metacarpus lead to increased joint pressures, thus increasing the risk of developing rhizarthrosis. A gender difference has been observed: women have more marked curvatures at these bone levels, which could explain their higher prevalence of this pathology.
Towards predictive tools and customized solutions
Thanks to this multi-scale model, researchers have been able to identify at-risk morphologies and pressures. This new modeling method opens up a wide range of possible applications. In fact, this is what the experts want to develop today alongside interested companies. They already have ideas for developments covering prediction, prevention and rehabilitation.
Several examples of applications can already be mentioned. These include a tool to predict the risk of developing rhizarthrosis, based on the patient's morphology and grip patterns. The aim is to provide precise information to enable practices to be adapted, thereby reducing long-term risks.
In cases where patients are unable to change their grip type, the experts also plan to develop in situ methods capable of analyzing the actual grip and supplementing it.
Another example: the model can already be used to simulate different types of surgery to test their effectiveness. Applied to each patient, this tool would also enable each surgical procedure to be adapted to the patient's specific morphological profile before proceeding with the operation... This individual diagnosis would be made possible thanks to a personalized model based on scanner imaging and intelligent motion capture.