Dominic Stone
The scapula, or shoulder blade, is a flat, triangular bone that connects the clavicle (collarbone) to the humerus (upper arm bone). It forms the back of the shoulder girdle and is connected to 17 muscles, 12 tendons, six ligaments, and two nerves. These connections allow the shoulder to move in six directions, more than any other joint in the body. The scapula has three surfaces, three borders, three angles, and three processes. The intrinsic muscles of the scapula include the rotator cuff muscles, teres major, subscapularis, teres minor, and infraspinatus. The extrinsic muscles include the triceps, biceps, and deltoid.
| Characteristics | Values |
|---|---|
| Common Name | Shoulder Blade |
| Latin Name | Scapula |
| Number of Bones | 2 |
| Shape | Flat and Triangular |
| Surfaces | 3 |
| Borders | 3 |
| Angles | 3 |
| Processes | 3 |
| Functions | Absorbs Contact, Protects the Chest, Provides Full-Functional Upper Extremity Movement |
| Muscles | Rotator Cuff (Subscapularis, Supraspinatus, Infraspinatus, Teres Minor), Biceps, Triceps, Deltoid, Levator Scapulae, Trapezius, Rhomboids, Serratus Anterior, Pectoralis Minor, Coracobrachialis, Latissimus Dorsi |
| Tendons | 12 |
| Ligaments | 6 |
| Nerves | 2 |
| Treatments for Disorders | Physical Therapy, Strengthening Shoulder Muscles, Restoring Scapula Position and Motion, Heat Therapy |
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What You'll Learn
- The scapula is well-protected, so fractures are rare
- The scapulothoracic joint allows the scapula to smoothly glide over the chest wall
- The rhomboids major and minor, and serratus anterior are scapular muscles
- Scapular dyskinesis can be treated with physical therapy
- Winging of the scapula is caused by nerve damage
The scapula is well-protected, so fractures are rare
The scapula, or shoulder blade, is a triangular-shaped bone that connects the clavicle to the humerus. It is responsible for providing rotational movement to the upper extremity and assisting with abduction and rotation at the glenohumeral joint. The scapula is also the attachment site for 18 muscles, which connect to the thorax, spine, and upper extremity.
The scapula is well-protected by the rib cage and thoracic cavity anteriorly and is covered with a lot of soft tissue, or muscle, posteriorly. This protection means that fractures to the scapula are rare, accounting for only 3-5% of shoulder girdle fractures and less than 1% of all fractures. The most frequent fractures are to the scapular body and spine, which make up 50% of cases.
Scapular fractures are typically the result of high-energy or high-impact direct trauma, and nearly all incidences are associated with other severe, life-threatening injuries. The force required to cause a fracture of the scapula varies, resulting in a wide variety of reported fracture patterns. Fractures can be classified based on the anatomical location on the scapula where the fracture occurred.
The treatment for scapular fractures is often conservative, with short-term immobilization and motion exercises to prevent frozen shoulder. Operative management is rarely required and should be delayed until the patient is stable and no longer at risk of other life-threatening injuries.
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The scapulothoracic joint allows the scapula to smoothly glide over the chest wall
The scapula, or shoulder blade, is a sturdy, flat, triangular bone that connects the clavicle to the humerus. It forms the posterior of the shoulder girdle and provides attachment to several groups of muscles. The scapulothoracic joint is not a true anatomical joint but is rather considered a unit that gathers the sternoclavicular and acromioclavicular (AC) joints and the junction between the anterior surface of the scapula and the thoracic cage (scapulothoracic junction). The scapulothoracic junction enables the mobility of the scapula around the fulcrum of the acromioclavicular joint, allowing the scapula to smoothly glide over the chest wall.
The scapulothoracic junction is a connection between the anterior surface of the scapula and the superolateral surface of the thoracic wall. The surfaces are separated by the subscapularis muscle, the serratus anterior muscle, and the fascial space between these two muscles. This fascial space is filled with loose connective tissue that facilitates the gliding movements of the scapula. The scapulothoracic junction is stabilized by the synchronized actions and passive tensions of three functional muscle units: the medial stabilizers of the scapula (levator scapulae and rhomboid muscles), the muscles of the chest wall, and the muscles of the back.
The scapula engages in six types of motion, enabling full-functional upper extremity movement: protraction, retraction, elevation, depression, upward rotation, and downward rotation. Protraction is accomplished by the actions of the serratus anterior, pectoralis major, and pectoralis minor muscles. Retraction is accomplished by the actions of the trapezius, rhomboids, and latissimus dorsi muscles. Elevation and depression refer to the scapula moving upward or downward along the rib cage from its resting position. These movements occur around a sagittal axis that passes through the centre of the acromioclavicular joint.
The levator scapulae is a slender skeletal muscle situated at the back and side of the neck. Its main function is to lift the scapula. When the shoulder is fixed, the levator scapulae rotates to the same side and flexes the cervical spine laterally. It often works in combination with other muscles, such as the rhomboids and pectoralis minor, to produce downward rotation of the scapula. The extrinsic muscles of the scapula, including the triceps, biceps, and deltoid, attach to the processes of the scapula and affect motion at the glenohumeral joint.
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The rhomboids major and minor, and serratus anterior are scapular muscles
The scapula, or shoulder blade, is a sturdy, flat, triangular bone that connects the clavicle to the humerus. It forms the posterior of the shoulder girdle. The scapula provides attachment to several groups of muscles, including the rotator cuff muscles, teres major, subscapularis, teres minor, and infraspinatus.
The serratus anterior is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth or ninth ribs at the lateral wall of the thorax and inserts along the superior angle, medial border, and inferior angle of the scapula. It acts on the scapula and is the prime mover in both scapular protraction and scapular upward rotation. It is a key scapular stabilizer, keeping the shoulder blades against the rib cage when at rest and during movement.
The rhomboids and serratus anterior work together with the levator scapulae and trapezius to produce rotational movements and stabilization of the scapula. They also work together to anchor the scapula and prevent winging. The serratus anterior is the antagonist muscle group to the rhomboids. The rhomboids also work in conjunction with the levator scapulae to elevate and retract the scapula.
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Scapular dyskinesis can be treated with physical therapy
Scapular dyskinesis (SD) is a physical impairment that affects the scapula's position and motion. It is also known as SICK scapula syndrome, referring to the change in the normal resting or active position of the scapula during movement. SD can cause pain and tenderness around the scapula, a snapping or popping sensation, and loss of strength in the shoulder and upper extremities. It is commonly associated with muscle weakness or imbalance, and can be caused by overuse or repetitive motions.
One specific exercise is the quad rock back, where the patient is placed in a quadruped position with equal weight bearing through all extremities. The patient then protracts the shoulders, pushes through the arms into the ground, and then pushes back onto their feet while maintaining pressure through their arms. This exercise assists with the upward rotation of the scapula during shoulder elevation and is effective in treating scapular winging.
Other techniques to correct scapular movement patterns include building strength and improving the range of control of the shoulder joint. This can help treat scapular dyskinesis and prevent future issues.
In addition to physical therapy, research has shown that Neuromuscular Electrical Stimulation (NMES) is effective in improving the motions of the scapula.
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Winging of the scapula is caused by nerve damage
The scapula, or shoulder blade, is a sturdy, flat, triangular bone that connects the clavicle to the humerus. The scapula forms the posterior of the shoulder girdle and provides attachment to several groups of muscles. The scapular muscles can be categorised into three topographic groups: the scapulohumeral, axiohumeral, and axioscapular groups.
Winging of the scapula is a condition where the shoulder blade sticks out instead of lying flat against the back and ribcage. It is caused by nerve damage, specifically to the nerves that control the muscles supporting the shoulder blade. The most common nerve affected is the long thoracic nerve, which can be injured during axillary dissection, trauma, or a thoracotomy. Other nerves that may be affected include the spinal accessory nerve and the dorsal scapular nerve.
The serratus anterior muscle, controlled by the long thoracic nerve, is often affected in scapular winging. When this muscle loses innervation, it can no longer provide stability to the scapula, leading to medial scapular winging. Lateral scapular winging, on the other hand, is due to damage to the trapezius or rhomboid muscles. The trapezius muscle is innervated by the spinal accessory nerve, while the rhomboid muscles are innervated by the dorsal scapular nerve.
Scapular winging can also be caused by primary injuries to the scapula bone itself or periscapular soft tissue abnormalities. Certain populations, such as women who have undergone chest surgery, particularly mastectomies, are more prone to developing scapular winging due to the proximity of the long thoracic nerve to other structures. Additionally, individuals who participate in sports or have physically demanding jobs that put a lot of stress on their shoulders are at a higher risk.
Winging of the scapula can cause considerable pain and affect the ability to perform daily activities. Treatment options include pain medications and physical therapy. Electrodiagnostic testing and neuromuscular ultrasound can be used to establish the underlying neuromuscular pathology and muscular pathology, respectively.
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