Inverse dynamics analysis as a complement of shoulder physical therapy assessment

Abstract

The purpose of this study was to describe forces acting on the shoulder joint during upper limb elevation at the scapular plane by means of the inverse dynamics method, here suggested as a complementary means of physiotherapeutic assessment of the shoulder. The method allows for determining proximal net moment (PNM) and proximal net force (PNF) peaks during movements, hence providing an objective assessment of loads on the joint. Twenty-one male subjects were studied, their shoulder movements being analysed by videogrammetry in three load situations: with and without load, and with elastic resistance. A three-dimensional mathematic model was used to calculate PNM and PNF peak values, as well as to describe their evolution during movement along the anterior-posterior, superior-inferior, and lateral-medial axes. The inverse dynamics method was thus shown to provide objective information on the loads which shoulder joint is submitted to at the diverse ranges of motion and load situations during arm elevation; such information may be taken as a factual basis for planning shoulder rehabilitation programs.