Biomedical Engineering Reference
In-Depth Information
Chapter 9
Combined Motions of the Shoulder Joint
Complex for Model-Based Simulation: Modeling
of the Shoulder Rhythm (ShRm)
Victor Sholukha and Serge Van Sint Jan
9.1 Anatomical and Articular Components of the Shoulder
Girdle Complex
The shoulder joint complex includes 4 bony segments showing articular relation-
ships with each other: the humerus (Hum) (1 in Fig.
9.1
), the scapula (Scap) (2), the
clavicle (Clav) (3) and the thorax (Thor) (4). For modeling purposes as presented
in this chapter, the thorax segment includes all ribs, sternum and thoracic vertebrae.
These bony components articulate with each other through several joints to define the
shoulder joint complex including: the scapulohumeral (or glenohumeral) joint (A),
the acromioclavicular joint (B), the sternoclavicular (or sternocostoclavicular) joint
(C) and the scapulothoracic joint (D). Each individual joint allows the related bony
components to move independently. However, the combined action of the shoul-
der joint ligament organization and the shoulder muscle control create a functional
synergy between these joints. This functional joint synergy is widely acknowledged
to follow a given pattern called the “
shoulder rhythm
” or ShRmmechanism as called
further in this chapter. Modeling activities should take this synergy into account in
order to reproduce the real shoulder behavior. Note that the literature sometimes
refers to the motions of the humerus relative to the thorax as taking place in a
so-called “
thoracohumeral joint
”. Anatomically, the latter joint does not exist. We
will use this term as synonym to the joint mechanism describing the entire ShRm
behavior that involves a synergy between all previously-mentioned anatomical joints.
