Supporting and Stabilizing the Scapulohumeral Rhythm With a Body- or Robot-Powered Orthosis

Abstract

The versatile functionality of the human upper limb is owed to the coordinated rotation of the scapula and humerus, a pattern called the scapulohumeral rhythm (SHR). Various medical conditions can alter the SHR, frequently leading to limitations in activities of daily living. However, to date, supporting the SHR in practice is often not feasible. We present a textile orthosis that assists the SHR both in stand-alone use and in combination with the ANYexo, a therapy exoskeleton, or the Myoshirt, an assistive exomuscle. The SHR Orthosis comprised a textile harness and a scapula interface that was coupled with the upper arm to promote scapular upward rotation. In a technical evaluation including four participants without impairments and one with a partial hemiparesis, the SHR Orthosis followed the desired scapular rotation with an average deviation of less than 5°, thus providing accurate support and guidance towards the physiological SHR. The SHR Orthosis substituted for ≤ 42.0 % of the normal forces, and ≤ 19.6 % of the tangential forces required for scapular stabilization and rotation, providing sufficient support for patients with remaining muscular function. At last, the SHR Orthosis provides practicable scapula support in daily life, during conventional therapy, and in combination with assistive and therapy robots.