Estimating shoulder complex mobility

Abstract

Modelling shoulder motions is essential in understanding upper limb dynamic behaviour. However, the mobility of the shoulder-complex - in terms of degrees of freedom - is seldom quantified. In this paper we propose applying the theory of mechanisms and, especially, the powerful Grübler-Kutzbach formula to estimate it. This approach requires a rigorous kinematic analysis so we suggest basing it on a bone schematization derived from an extension of Demspter's historical notation associated to a mechanical interpretation of the physiological joints involved. So doing, the proposed shoulder complex mobility leads to justifying a 9 d.o.f serial chain upper limb mode ,which extends the classical 7 d.o.f. arm-foream-wrist model and completing it by adding a clavicle-like link with a 2 d.o.f. mobility.