The shoulder joint is a muscle-dependent joint because it lacks strong ligaments. The main shoulder stabilizers include the biceps brachial on the front of the arm and the tendons of the rotator cuff; Fused on all sides of the capsule except the bottom margin. The tendon of the long head of the biceps brachial passes through the bicipital groove of the humerus and settles at the upper edge of the glenoid cavity to press the head of the humerus against the glenoid cavity. [3] The rotator cuff tendons and their respective muscles (supraspinatus, infraspinatus, teres minor and subscapularis muscles) stabilize and fix the joint. The supraspinatus, infraspinatus and teres minor muscles support abduction and external rotation. The GH, AC and SC joints connect the upper limb to the axial skeleton of the chest. The ST joint allows the shoulder blade to slide over the contours of the posterior chest wall. The four joints work together to achieve normal movements of the shoulder girdle. [1] Shoulder complex movements represent a complex dynamic relationship between muscle forces, ligament restrictions, and bone joints. The articular structures of the shoulder complex, especially the GH joint, are mainly designed for mobility, which allows us to move and position the hand in a wide space, allowing the greatest range of motion of a joint in the body. [1] [2] The shoulder consists of a patella formed by the bones of the humerus and shoulder blades and their surrounding structures – ligaments, muscles, tendons – which support the bones and maintain the relationship with each other. [1] [2] These support structures attach to the clavicle, humerus and scapula with the latter providing the glenoid cavity, acromion and coracoid process.
The main joint of the shoulder is the shoulder joint (or glenohumeral joint), between the humerus and the glenoid process of the scapular. [1] The acromioclavicular joint and the sternoclavicular joint also play a role in shoulder movements. [3] The white hyaline cartilage at the ends of the bones (called articular cartilage) allows the bones to slide and move over each other, and the joint space is surrounded by a synovial membrane. Around the joint space are muscles — the rotator cuff that directly surrounds and attaches the shoulder joint — and other muscles that provide stability and facilitate movement. Joint cartilage is often thinner in the shoulder than in stressful joints such as the knees and hips. If the articular cartilage of the shoulder is damaged, it can significantly affect the shoulder`s ability to resist friction and shock. The shoulder is made up of a network of bones, joints and soft tissues that allow this wide range of motion. Under the influence of testosterone and growth hormone, the shoulders in men expand during puberty. [18] The rotator cuff muscles of the shoulder produce high pulling force and help pull the humeral head into the glenoid cavity. The most common shoulder injuries affect muscles, ligaments, cartilage and tendons, not bones. Common shoulder injuries include rotator cuff tears, shoulder conflict, and dislocation.
Athletes, such as tennis or soccer players, and people who work in occupations that require frequent and heavy aerial lifting, are most likely to injure their shoulders. Biceps tendons are the two tendons that connect the biceps muscle from the upper arm to the shoulder. They are called the long head and the short head of the biceps. The innervation of the glenohumeral joint is a function of the suprascapular, lateral thoracic and armpit nerves. All the nerves supplying the glenohumeral joint originate from the brachial plexus, a network of nerves formed by the ventral rummy of the four lower cervical nerves and the first thoracic nerve (C5, C6, C7, C8 and T1). The anatomy of the axillary nerve is critical because it is located near the glenohumeral joint. The axillary nerve originates from the posterior strand of the brachial plexus, runs along the subscapularis to its lower edge, and then closely runs along the inferior glenohumeral joint capsule. It then extends behind the humerus, wraps around the surgical neck of the humerus with the posterior circumflex artery and runs into the deep delta fascia. The development of the skeletal shoulder consists of two forms of ossification processes. The clavicle undergoes intramembranous ossification, which is the direct deposition of bone in the mesenchyme.
The rest of the bone structures of the shoulder are formed by endochondral ossification. [15] The germ layer of the mesoderm forms almost all of the connective tissue of the musculoskeletal system, including the glenohumeral joint. Musculoskeletal and limb anomalies, due to both environmental and genetic contributions, constitute one of the largest groups of congenital anomalies. The scapulohumeral rhythm is a common measure for assessing muscle function and movement of shoulder joints. [26] There is a three-dimensional scapular kinematic pattern during normal arm elevation that includes upward rotation, posterior tilt, and variable internal/external rotation depending on plane and elevation angle. [21] [22] When the normal position of the scapula changes in relation to the humerus, it can lead to dysfunction of the scapulohumeral rhythm, often referred to as scapular dyskinesia. The rotator cuff is the main muscle group of the shoulder joint and consists of 4 muscles. The rotator cuff forms a cuff around the humeral head and glenoid cavity, which gives additional stability to the shoulder joint while allowing a wide range of mobility. The deltoid muscle forms the outer layer of the rotator cuff and is the largest and strongest muscle in the shoulder joint. Ultrasound has several advantages. It is relatively cheap, does not emit radiation, is accessible, can visualize tissue function in real time, and allows for provocative maneuvers to replicate the patient`s pain. [26] These benefits have helped make ultrasound a common first choice for tendon and soft tissue assessment.
Limitations include, for example, high dependence on the operator and inability to define pathologies in the bones. You should also have a thorough anatomical knowledge of the area being studied and be open to normal variations and artifacts that occur during the scan. [27] The price of being the most mobile joint in the body is that the glenohumeral joint is unstable and prone to dislocation. Anterior dislocations are the most common, accounting for 97% of all dislocations. The typical cause is a blow to a kidnapped member, facing outwards and lying down. Anterior dislocation can damage the axillary nerve, leading to paralysis of the deltoid muscle and decreased skin sensation on the shoulder, as well as torn ligaments and fractures. Patients usually restore the functionality of the axillary nerve with a reduction of the humeral head in the glenoid fossa. Posterior dislocations are less common, but associated with convulsions. The risk of rotator cuff tears and ligaments with posterior dislocations is higher than that of anterior dislocations. Lower dislocations are very rare and are the result of hyperabduction.
They have the highest incidence of axillary nerve and artery damage. The capsule can become inflamed and stiff, with abnormal ligaments of tissue (adhesions) developing between joint surfaces, causing pain and limiting shoulder movement, a condition known as frozen shoulder or adhesive capsulitis. The intrinsic muscles of the shoulder connect the shoulder blade and/or clavicle to the humerus. These include[1] Shoulder imaging includes ultrasound, X-ray, and MRI and is based on the diagnosis and suspected symptoms. The end of the humerus or humerus forms the ball of the shoulder joint. A shallow irregular cavity in the shoulder blade, called the glenoid cavity, forms the cavity into which the humeral head fits. The two bones together form the glenohumeral joint, which is the main joint of the shoulder. Shoulder pain affects about 18 million Americans each year, most of which are due to rotator cuff tears. The tear may occur due to a mixture of trauma, overuse, or age-related degeneration, and may be asymptomatic or cause severe pain and decreased mobility. Research has shown that smoking, high cholesterol and family history all predispose to tears.
