Rôle des ligaments interosseux dans la stabilité transverse de l’articulation radio-ulnaire proximale. Étude d’un modèle validé en éléments finis

Transverse stability of the proximal radio-ulnar joint (PRUJ) is a major issue in secondary surgeries of Monteggia fractures. To restore this stability, surgeons perform osteotomies and ligamentoplasties. Ligament surgeries focus on annular ligament but recently, a cadaveric study of Anderson et al. pointed out a possible major role of the central band in the PRUJ transverse stability, especially when the annular ligament is cut. Computational models using patient-specific bone geometry, such as finite element models (FE) can complement such cadaveric studies by defining the stress distribution carried by each forearm ligament. The purpose of this project is to develop and validate a novel FE model to study the particular influence of each ligament in the PRUJ. The model will be validated against data from a published cadaveric study. Bone geometry was obtained from a cadaveric CT. Six forearm ligaments were modeled according to anatomical studies. A non-linear force strain relationship were attributed to ligaments in accordance with Werner et al. Reproducing Anderson's study, the ulna was fixed and a displacement from 0 to 3 mm was applied on the radius in a transverse direction from the ulna. The main ligaments were then virtually cut in a sequential manner. Transverse forces were collected and compared to Anderson's study for validation of the model. Then, the stress induced by each ligament for the same applied transverse force was studied, and compared after cutting only one individual ligament at a time. Incremental sectioning of the ligaments reduced the force required to reach the same displacement in the same way it did in the cadaveric study of Anderson et al. The stress study showed a major increase of the central band stress when the annular ligament is cut, focusing 92% of the total stress. A FE model of the forearm including ligaments is reliable considering the PRUJ transverse stability. The central band plays a major role, especially when the annular ligament is injured and this has to be taken into consideration in forearm secondary surgery. These finding have to be confirmed during the forearm rotation. Using a validated FE model, the stress distribution in ligaments can be analyzed precisely and independently, a task not easily replicable in an in vitro setting, and it confirmed the cadaveric hypothesis. Furthermore, the developed model can potentially be used to accurately evaluate a variety of ligamentoplasties on the transverse stability of the PRUJ.