Every year in Germany, some 270,000 people suffer a stroke, that is to say a circulatory disorder of the brain. Various functions of the body can fail and signs of paralysis may result because areas of the brain are no longer supplied sufficiently. If the humerus can no longer be held in the joint socket with muscle strength, it moves in-part out of the glenoid cavity. Therefore, unilateral paralysis in the shoulder results in subluxation. Moreover, the arm turns increasingly towards the body (internal rotation). The BOA® fit pulley system integrated in the BORT OmoControl guides the arm concerned back towards its natural joint position again. The previously overburdened anatomical structures enjoy relief as a consequence. The arrangement of the pulley system and its deviation points support the arm position from internal rotation to external rotation.