Shoulder joint
Last reviewed: 23.04.2024
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The shoulder joint (art humeri) is formed by the articular cavity of the scapula and the head of the humerus. The articular surface of the head is spherical, almost 3 times larger than the flat surface of the articular cavity of the scapula. The articular cavity is supplemented along the edges by the labrum glenoidale (labrum glenoidale), which increases the congruence of articular surfaces and the capacity of the articular fossa. The joint capsule is attached to the outer side of the joint lip, as well as to the anatomical neck of the humerus. The capsule of the shoulder joint is thin, strained slightly, loose. Above, the joint capsule is strengthened by the only coracoid-brachial ligament (lig. Coracohumerale), which starts at the base of the coracoid process of the scapula and is attached to the upper part of the anatomical neck of the humerus. In the capsule, weave fibers of tendons located next to the muscles (subscapular, etc.). The synovial membrane of the joint capsule forms two protrusions. One of them - the intercampoon synovial vagina (vagina synovialis intertubercularis), like a case, surrounds the tendon of the long head of the biceps arm muscle passing through the joint cavity. The second protrusion is the subcutaneous bag of the subscapular muscle (bursa subtendinea m. Subscapularis) located at the base of the coracoid process, under the tendon of this muscle.
According to the shape of articular surfaces, the shoulder joint is spherical. It has a large amplitude of motion around the three axes, facilitated by a free joint capsule, a large difference in the size of the articulating surfaces, the absence of powerful ligaments. Around the front axis, flexion and extension are performed. The range of these movements is, in total, approximately 120 °. Concerning the sagittal axis, the lead (to the horizontal level) is carried out and the hand is brought. The range of motion is up to 100 °. With respect to the vertical axis, povots are possible outwards (supination) and inward (pronation) with a total volume up to 135 °. In the shoulder joint, circular movements (circumductiio) are also performed. Movement of the upper limb above the horizontal level is performed in the chest and in the clavicle joint when the scapula is raised together with the free upper limb.
On the roentgenogram of the shoulder joint, the head of the humerus, the articular cavity of the scapula, is clearly defined. The contours of the lower medial part of the head are layered on the articular cavity of the scapula. The x-ray gap in the image has the form of an arc-shaped strip.
Movement of the shoulder in the shoulder joint: flexion - extension (around the front axis) - within 120 °; lead - reduction (around the sagittal axis) - 70-80 °; Rotation around the longitudinal axis - 135 °.
The shoulder is removed: the deltoid muscle, the supraspinatus muscle.
Lead the shoulder: a large pectoral muscle, the widest back muscle, a subscapular muscle, a subacute muscle.
The shoulder is bent: the deltoid muscle (front fascicles), the large pectoralis muscle, the biceps arm muscle, the beak-brachial muscle.
Unbend the shoulder: deltoid muscle (posterior fascicles), triceps brachium (long head), broadest back muscle, large round muscle, subacute muscle.
Turn the shoulder inwards: the deltoid muscle (front fascicles), the large pectoral muscle, the broadest muscle of the back, the large round muscle, the subscapular muscle.
Turn the shoulder outward: the deltoid muscle (the posterior fascicles), the large round muscle, the subacute muscle.
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