A parallel mechanism of the shoulder - application to multi-body optimisation

Aimad El Habachi (1) , Sonia Duprey (2) , Laurence Cheze (2) , Raphaël Dumas (2)

1 UCBL - Université Claude Bernard Lyon 1
2 LBMC UMR T9406 - Laboratoire de Biomécanique et Mécanique des Chocs

This paper describes and evaluates a parallel mechanism of the shoulder girdle. This mechanism was a closed kinematic chain composed of three segments (humerus, scapula and thorax) and three kinematic constraints. The clavicle was modelled as a constant length constraint between the sternoclavicular and acromioclavicular joint centres. The second kinematic constraint was also a constant length between the glenoid cavity and the humeral head for the glenohumeral joint. The third constraint was a point-on-ellipsoid contact for the scapulothoracic joint. Geometrical data required to build this kinematic model were obtained from the Visible Human Project. The parallel mechanism was then introduced into a multi-body optimisation for the computation of the scapulothoracic joint angles from surface sensors during the abduction of the arm of six able-bodied subjects. The initial guess of this optimisation was obtained by an acromial method. Compared to palpation of scapula anatomical landmarks, the multi-body optimisation with the proposed parallel mechanism allows estimating the shoulder kinematics with a better accuracy than the acromial method alone.

Mots clés: SHOULDER GIRDLE; ACROMIAL METHOD; PALPATION; KINEMATIC CONSTRAINTS; SCAPULOTHORACIC JOINT ANGLES

Mots clés: BIOMECANIQUE; CORPS HUMAIN

Domaines: Ingénierie biomédicale

Aimad El Habachi, Sonia Duprey, Laurence Cheze, Raphaël Dumas. A parallel mechanism of the shoulder - application to multi-body optimisation. Multibody System Dynamics, 2015, 33 (4), pp. 439-451. ⟨10.1007/s11044-014-9418-7⟩. ⟨hal-01129014v2⟩