{"id":921,"date":"2014-03-28T22:57:29","date_gmt":"2014-03-29T05:57:29","guid":{"rendered":"http:\/\/bestperformancegroup.com\/?page_id=921"},"modified":"2016-02-27T18:30:52","modified_gmt":"2016-02-28T01:30:52","slug":"scapula-anatomical-considerations","status":"publish","type":"page","link":"http:\/\/bestperformancegroup.com\/?page_id=921","title":{"rendered":"Shoulder Complex – Anatomical Considerations"},"content":{"rendered":"

The complex construction of the shoulder complex provides a unique mobility that surpasses the mobility of any other joint in the body.\u00a0 While it incorporates a ball-and-socket joint, similar to the hip, the shoulder joint has a more limited bony interface which provides much greater mobility than the hip joint, another ball-and-socket joint. \u00a0The shoulder must be mobile enough for the variety of movements required of the arms and hands, but also stable enough to allow for actions such as lifting, pushing and pulling.<\/p>\n

\"shldrgirdle\"<\/a><\/p>\n

The shoulder girdle acts as a movable but steady support for the motions of the humerus. \u00a0The shoulder girdle has 2 bones (clavicle and scapula) that move together as a unit. \u00a0To maintain its integrity, the shoulder girdle depends more on muscles than on joint structures. \u00a0Because the\u00a0upper limb\u00a0is not usually involved in weight bearing, its stability has been sacrificed in exchange for greater mobility. \u00a0Such a construction provides dynamic stability to the complex, i.e. greater mobility and stability at the same time through muscular contractions.<\/p>\n

\"shldrcomplex2\"<\/a><\/p>\n

The arm is connected to the trunk through the shoulder mechanism, a constellation of four bones (humerus, scapula, clavicle, and thorax). \u00a0There are 4 different articulations that make up the shoulder girdle complex:<\/p>\n

    \n
  1. Glenohumeral<\/strong><\/span> – the synovial ball and socket joint\u00a0articulation between the\u00a0glenoid fossa\u00a0of the\u00a0scapula\u00a0and the\u00a0head of the humerus. \u00a0This joint is what most people associate with the shoulder joint. \u00a0The surface arae of the humeral head is much larger than the surface of the glenoid fossa, and only a part of the humeral head touches the glenoid.\u00a0 Thus, the joint is inherently unstable. \u00a0The glenohumeral joint has 3 rotational degrees of freedom (DOF).<\/li>\n
  2. Acromioclavicular (AC)<\/strong><\/span> – aka claviculoscapular joint,\u00a0at the top of the\u00a0shoulder\u00a0between the\u00a0acromion\u00a0of the\u00a0scapula (highest point of the shoulder) and the lateral\u00a0clavicle. \u00a0In the transverse plane, the angle between the scapular spine and the clavicle is approximately 50 degrees.\u00a0 In the joint, the scapula moves on the clavicle.\u00a0 The joint has three rotational DOF.<\/li>\n
  3. Sternoclavicular<\/span><\/strong> – compound joint in which the clavicle articulates with the manubrium of the sternum and the cartilage of the first rib.\u00a0 The joint cavity is divided into two compartments by the articular disk.\u00a0The sternoclavicular joint is the only joint that connects the shoulder complex to the axial skeleton.<\/li>\n
  4. Scapulothoracic<\/span><\/strong> –\u00a0formed by the female surface of the scapula and the male surface of the thorax.\u00a0 This is a bone-muscle-bone articulation that is not synovial and, in the true sense, is not a joint.\u00a0 However, considering it a joint is of some value when describing motion of the scapula over the thorax.\u00a0 The mating surfaces are separated by the subscapularis and serratus anterior muscles, which glide over each other during motion.\u00a0 The scapulothoracic articulation allows translation and rotatory movement of the scapula with respect to the rib cage.<\/li>\n<\/ol>\n

    \"scapularplane\"<\/a><\/p>\n

    The scapula lies obliquely over the ribs between the frontal and coronal planes.\u00a0 The angle between the frontal plane and the plane of the scapula, called the protraction or winging angle, is typically between 30\u00b0-45\u00b0\u00a0with an average of 35\u00b0. \u00a0The scapula is also anteriorly tilted 10\u00b0 and upwardly rotated 5\u00b0. \u00a0The plane of the glenoid is approximately at right angles to the plane of the scapula.\u00a0 The scapula has no bony and ligamentous connections with the chest.<\/p>\n

    The following video provides a very good review of the shoulder girdle.<\/p>\n