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Anatomy of the shoulder
The shoulder joint, as it is commonly called, is not a single joint but a complex arrangement of bones, ligaments and musculotendinous units that called the shoulder girdle. The primary role of the shoulder girdle is to provide a tremendous range of motion for positioning the upper extremity in space. The shoulder girdle also provides power and support for the upper extremity throughout and at the extremes of the range of motion. (19) The shoulder girdle includes three bones (scapula, clavicle, and proximal humerus), three joints (glenohumeral, acromioclavicular and sternoclavicular), an additional articulation (scapulothoracic) and some 17 musculotendinous units. These individual elements function in a synchronous and interdependent manner to maximize the power and range of motion of the shoulder girdle.(19)
glenohumeral joint (shoulder joint):
a- Humeral head: Articular portion approximates 1/3 of a sphere medially angulated 45 degrees and retroverted 30 degrees relative to the humeral shaft. b- Glenoid fossa: The surface of the glenoid fossa is only one third to one quarter that of the humeral head, The glenoid surface is pear-shaped being approximately 20% narrower superiorly than inferiorly with average vertical and transverse dimensions of 35 mm and 25 mm respectively. The glenoid has average superior tilt of 5º and is retroverted in average of 7º. With the arm hanging at side in the adducted position, the scapula tilts 30º anteriorly and tilts 3º upward on the coronal plane (Figure 12) .(20) Fig (12): Orientation of the glenoid. A- The superior tilt of the glenoid. B-Retroversion angles of the glenoid and the humeral head. (20) sternoclavicular joint : The sternoclavicular joint is a double gliding joint with an articular disc. Its ligaments include the capsule, anterior and posterior sternoclavicular ligaments, an interclavicular ligament, and a costoclavicular ligament. The sternoclavicular joint rotates 30 degrees with shoulder motion. Acromioclavicular joint : The acromioclavicular joint is a plane gliding joint that also possesses a disc. Its ligaments include the capsule, acromioclavicular ligament, and coracoclavicular ligament. (3) The scapulothoracic articulation : The Scapulothoracic articulation is not a true anatomic joint as it has none of the usual joint characteristics (union by fibrous, cartilaginous, or synovial tissues). It is an articulation of the scapula with the thorax which depends on the integrity of the anatomic acromioclavicular and sternoclavicular joints. The sternoclavicular and acromioclavicular joints are interdependent with the scapulothoracic articulation because the scapula is attached by its acromion process to the lateral end of the clavicle & through the acromioclavicular joint; the clavicle, in turn, is attached to the axial skeleton at the manubrium of the sternum through the sternoclavicular joint. Any movement of the scapula on the thorax must result in movement at either the sternoclavicular joint, the acromioclavicular joint, or both; that is, the functional Scapulothoracic articulation is part of a true closed chain with the acromioclavicular and sternoclavicular joints and the thorax . Movements of scapulothoracic articulation are a very important element of shoulder joint, the wide range of motion available to the shoulder joint due to the large movement available at scapulothoracic articulation .(21) Muscles of the Shoulder and Shoulder Girdle: Muscles of the shoulder serve a variety of functions. Five muscles help connect the upper limb to the vertebral column (trapezius, latissimus,both rhomboids, and the levator scapulae). Four muscles connect the upper limb to the …show more content…
The proximal origin of the muscle is on the spinous processes of thoracic vertebrae 7–12, the thoracolumbar fascia, the iliac crest, and the lower ribs (Figure14). The tendon is attached to the humerus anteriorly floor of bicipital groove. The tendon is either wing-like or quadrilateral. Most of the deep surface of the tendon of the latissimus dorsi is separated from the underlying tendon of the teres major muscle by a bursa. The latissimus dorsi has several different functions, all of which involve movements of the arm. The primary function is the adduction of the arm, another function of the latissimus dorsi is extension of the arm, as in swinging the arm toward the back. Finally, the latissimus dorsi medially rotates the arm. The latissimus dorsi is supplied by the sixth, seventh, and eighth cervical nerves through the thoracodorsal (long scapular) nerve a branch from posterior cord C 6, 7, and 8.
Anatomy of the shoulder
The shoulder joint, as it is commonly called, is not a single joint but a complex arrangement of bones, ligaments and musculotendinous units that called the shoulder girdle. The primary role of the shoulder girdle is to provide a tremendous range of motion for positioning the upper extremity in space. The shoulder girdle also provides power and support for the upper extremity throughout and at the extremes of the range of motion. (19) The shoulder girdle includes three bones (scapula, clavicle, and proximal humerus), three joints (glenohumeral, acromioclavicular and sternoclavicular), an additional articulation (scapulothoracic) and some 17 musculotendinous units. These individual elements function in a synchronous and interdependent manner to maximize the power and range of motion of the shoulder girdle.(19)
glenohumeral joint (shoulder joint):
a- Humeral head: Articular portion approximates 1/3 of a sphere medially angulated 45 degrees and retroverted 30 degrees relative to the humeral shaft. b- Glenoid fossa: The surface of the glenoid fossa is only one third to one quarter that of the humeral head, The glenoid surface is pear-shaped being approximately 20% narrower superiorly than inferiorly with average vertical and transverse dimensions of 35 mm and 25 mm respectively. The glenoid has average superior tilt of 5º and is retroverted in average of 7º. With the arm hanging at side in the adducted position, the scapula tilts 30º anteriorly and tilts 3º upward on the coronal plane (Figure 12) .(20) Fig (12): Orientation of the glenoid. A- The superior tilt of the glenoid. B-Retroversion angles of the glenoid and the humeral head. (20) sternoclavicular joint : The sternoclavicular joint is a double gliding joint with an articular disc. Its ligaments include the capsule, anterior and posterior sternoclavicular ligaments, an interclavicular ligament, and a costoclavicular ligament. The sternoclavicular joint rotates 30 degrees with shoulder motion. Acromioclavicular joint : The acromioclavicular joint is a plane gliding joint that also possesses a disc. Its ligaments include the capsule, acromioclavicular ligament, and coracoclavicular ligament. (3) The scapulothoracic articulation : The Scapulothoracic articulation is not a true anatomic joint as it has none of the usual joint characteristics (union by fibrous, cartilaginous, or synovial tissues). It is an articulation of the scapula with the thorax which depends on the integrity of the anatomic acromioclavicular and sternoclavicular joints. The sternoclavicular and acromioclavicular joints are interdependent with the scapulothoracic articulation because the scapula is attached by its acromion process to the lateral end of the clavicle & through the acromioclavicular joint; the clavicle, in turn, is attached to the axial skeleton at the manubrium of the sternum through the sternoclavicular joint. Any movement of the scapula on the thorax must result in movement at either the sternoclavicular joint, the acromioclavicular joint, or both; that is, the functional Scapulothoracic articulation is part of a true closed chain with the acromioclavicular and sternoclavicular joints and the thorax . Movements of scapulothoracic articulation are a very important element of shoulder joint, the wide range of motion available to the shoulder joint due to the large movement available at scapulothoracic articulation .(21) Muscles of the Shoulder and Shoulder Girdle: Muscles of the shoulder serve a variety of functions. Five muscles help connect the upper limb to the vertebral column (trapezius, latissimus,both rhomboids, and the levator scapulae). Four muscles connect the upper limb to the …show more content…
The proximal origin of the muscle is on the spinous processes of thoracic vertebrae 7–12, the thoracolumbar fascia, the iliac crest, and the lower ribs (Figure14). The tendon is attached to the humerus anteriorly floor of bicipital groove. The tendon is either wing-like or quadrilateral. Most of the deep surface of the tendon of the latissimus dorsi is separated from the underlying tendon of the teres major muscle by a bursa. The latissimus dorsi has several different functions, all of which involve movements of the arm. The primary function is the adduction of the arm, another function of the latissimus dorsi is extension of the arm, as in swinging the arm toward the back. Finally, the latissimus dorsi medially rotates the arm. The latissimus dorsi is supplied by the sixth, seventh, and eighth cervical nerves through the thoracodorsal (long scapular) nerve a branch from posterior cord C 6, 7, and 8.