A kinematic model of the wrist based on maximization of joint contact area

Abstract

The wrist is a complex joint and the factors governing its behaviour are poorly understood. A hypothesis that the movement of the carpal bones could be predicted using a minimum energy principle was tested. Carpal bones were dissected from a cadaveric forearm and their shapes were laser-digitized to obtain three-dimensional computer models. A computer program was created to measure contact area between neighbouring articular surfaces and to maximize this quantity by adjusting the six degrees of freedom of the bone models. This procedure was performed for 1.0 degree increments of rotation applied to the capitate bone up to 20 degrees of ulnar and 10 degrees of radial deviation. The model correctly predicted certain aspects of the complex behaviour of the carpal bones. The results for the scaphoid in particular displayed characteristics in common with known behaviour of this bone. During 20 degrees of unlar deviation and 10 degrees of radial deviation, the bone demonstrated 11.3 degrees of extension and 9.4 degrees of flexion respectively. The novelty of the study lay in the fact that the model did not rely upon ligamentous constraints. The results are encouraging, considering the only information used by the algorithm was the shape of the articular surfaces.

2007 IFSSH Committee Report of Wrist Biomechanics Committee: Biomechanics of the So-Called Dart-Throwing Motion of the Wrist

“…38 Such a strategy would minimize the bone mass requirements, thereby minimizing the biological "cost" of creating and maintaining the joint. This agrees with the minimum energy principle, which governs many natural processes.…”

A Systematic Methodology to Analyze the Impact of Hand-Rim Wheelchair Propulsion on the Upper Limb

“…All these connections make the wrist to be a complex joint. Most of the wrist motion happens in the radiocarpal joint, in which the radius connects with the bones and the one in which the model focuses [33]. Therefore, the model takes into account this musculoskeletal system by defining the three different segments shown in Table 4, trunk, arm and hand.…”

Development of a kinematic 3D carpal model to analyze in vivo soft-tissue interaction across multiple static postures

“…We used in vitro determined values for S cart , the cartilage stiffness parameter, K lig , the ligament elasticity coefficient, and the scaphoid mass (Table I) [10], [11]. In the absence of stiffness and elasticity constants for the human wrist, material parameters representative of the human knee were used for the wrist cartilage and ligaments.…”