Gross Anatomy of the Shoulder

We are faced with a paradox in shoulder anatomy. Knowledge regarding the details of shoulder anatomy has increased along with knowledge regarding its clinical significance. However, our exposure is decreasing. The proportion of the medical school curriculum dedicated to anatomy is shrinking, and at the same time, a number of open procedures, where residents and students might observe the anatomy firsthand, have been replaced by arthroscopic procedures (Fig. 3.1). This decreased exposure has been offset by new imaging techniques that enable a deeper understanding of the current anatomy, both normal and abnormal , of the patient. Magnetic resonance imaging (MRI) allows a more detailed anatomic study of the patient, and ultrasound adds the ability to dynamically observe some structures. This chapter details the anatomic structures of the shoulder. According to the concept of a layered portrait, the material is arranged in a layered fashion. The discussion begins with the innermost layer, the bones and joints, which are the most palpable and least deformable structures of the shoulder. They are the easiest to visualize and are the best understood anatomic landmarks. We then reveal the muscle layers that enable motion of the shoulder and the nerves that direct the muscles and provide sensation. We will discuss the vessels that control the internal environment of the tissues of the shoulder and, finally, the skin that encloses the shoulder. The central theme of the shoulder is motion. The amount of motion in the shoulder sets it apart from all other joints and accounts for the manner in which the shoulder differs from all other regions of the body.