A New Algorithm to Estimate Glenohumeral Joint Location Based on Scapula Rhythm.

This work analyzes the human shoulder complex workspace by introducing a new method to estimate the intraarticulation location of the glenohumeral (GH) joint. The proposed algorithm is based on the hypothesis of the GH joint remaining fixed during the first 30 degrees of shoulder elevation. This part of any vertical movement is considered to estimate the center of spherical motions CoS) where the humeral head is located.For the experimental results, six subjects performed 5 cycles of 12 different movements in different planes. The data are collected using motion capture, for various landmarks of the shoulder girdle. With the proposed method, estimating the location of GH is possible for any motion of the shoulder girdle complex. In order to complete the kinematic model of the shoulder complex, PCA is used to identify a relation between the shoulder joints. This technique indicates that the shoulder complex can be modeled using two degrees of freedom (DOFs) to locate the spherical GH joint. The overall shoulder model can generate any possible vertical motion of the human shoulder.