Scapula, its borders, angles, and surfaces

Scapula

In human anatomy scapula also called shoulder bone, shoulder blade, or wing bone is the type of bone that connects the humerus with the clavicle. Scapulae are two in number and are roughly mirror images of each other. It is a flat and triangular bone located on the posterolateral aspect of the rib cage.

What is the structure?

The scapula is a wide and triangular bone to which three groups of muscles are attached. The groups of muscles that attached to the human scapula are the extrinsic muscles, intrinsic muscle, and rotating muscles. The intrinsic muscles include subscapularis, teres minor, supraspinatus, and infraspinatus. The extrinsic muscles include biceps, triceps, and deltoid muscles. Rotating or stabilizing muscles include the trapezius, serratus anterior, levator scapulae, and rhomboid muscles.

Cancellous tissue is present in the thickened part, head, and the process of this bone. The rest area of this bone consists of compact tissue.

Scapula anatomy

What are the surfaces of the scapula?

The front part of this bone has a concavity called a subscapular fossa. Subscapularis muscle attached to the subscapular fossa. The medial two third of the fossa has three ridges. The lateral third of the fossa is smooth. At the upper side of the fossa, a transverse depression is present that form an angle called a subscapular angle.

The dorsal surface of the scapula is divided into two parts by a structure called the spine of the scapula. the two parts are the supraspinatus fossa and infraspinatus fossa. The supraspinatus fossa is small and concave while the infraspinatus fossa is large that show concavity in its upper part and convexity in its central part.

Side

Acromion is present on the side. Acromion is a large triangular or oblong process that flattened from behind forward.

 

what are the Angles of this bone?

Three types of angles are present in the scapula that superior angle, medial angle, and lateral angle.

1. superior angle. The superior angle also called the medial angle is formed by the junction of the medial and superior border of the scapula. This angle is covered by the trapezius muscle and is thin, smooth, and rounded.

2.  Inferior angle. It is the lowest part that is formed by the union of medial and lateral borders of the scapula. This angle is covered by the lattisimus Dorsi muscle. The vertical plane that passes through the inferior angle of the scapula is called the scapular line.

3. lateral angle. The lateral angle also called the glenoid angle is the thickest part that bears the glenoid cavity. The glenoid cavity is directed forward laterally and articulates with the head of the humerus.

borders of this bone

Borders of the scapula are

1. Superior border. The superior border is short and thin that extends from the superior angle of the scapula to the base of the coracoid process. On its lateral side scapular notch is present that is converted into the foramen by the transverse scapular ligament.

2. Axillary border. The axillary border also called the lateral border is thick and begins above the lower margin of the glenoid cavity and extends up to the inferior angle.

3.  Medial border. The medial border also called the vertebral border is the longest border that extends from the superior angle to the inferior angle.

muscles attached to this bone

The muscles that attached to the scapula are

1.   Pectoralis minor
2.   Omohyoid
3.   Lattisimus Dorsi
4.   Teres major
5.   Teres minor
6.   Infraspinatus
7.   Supraspinatus
8.   Deltoid
9.   Trapezius
10.   Levator Scapulae
11.   Rhomboid minor
12.    Rhomboid major
13.    Subscapularis
14.    Bicep brachii long head and short head
15.    triceps brachii
16.    Serratus anterior
17.    Coracobrachialis

 

the movements produced by the scapula

The movements that are produced by the scapula are

1. Elevation
2.  Depression
3.   Retraction
4.   Protraction
5.   Upward rotation
6.   Downward rotation

 

winged scapula

It is a condition in which the shoulder bone protrudes in an abnormal position.  This condition can affect many abilities of a person such as lifting, pulling, and pushing.

winging of the scapula

Winging of the scapula is a condition in which the scapula become winged. On the basis of the direction, the winging of the scapula is divided into two types that are medial winging and lateral winging.

Causes

1. Medial winging is caused by serratus anterior paralysis that occurs due to damage of long thoracic nerve. 2.  Lateral winging occurs due to the injury of the spinal accessory nerve which causes the severe atrophy of the trapezius muscle.

Symptoms

Winging of the scapula occurs due to many muscles and nerves, therefore, it’s severity depends on the type of muscle and nerve that were affected.

Some of the common symptoms are
1. Deformation of the back
2.  Limited ability to lift the arm above the head.
3.  Scapula may slip away from the run cage.
4.  Pain is present but not in all cases.

 
Diagnosis

Diagnosis can be done through

1. History of the patient
2.  Examination
3.  Projectional radiography
4.   Computed tomography
5.   MRI.

Treatment

Treatment options are
1. Muscle strength training
2.  Physical therapy
3.  Surgery
4.   Neurolysis
5.   Intercostal nerve transfer
6.    Scapulothoracic fusion
7.    Arthrodesis.

Scapula pain

Pain in the scapula may occur due to the trauma to the shoulder area or due to the referred pain.

Causes

1. Muscle strain
2. Fractures that are uncommon
3. Osteoporosis
4. Collapsed or displaced discs.
5. Pericarditis
6.  Aortic dissection
7.  Lung cancer
8.  Mesothelioma
9.  Pulmonary emboli (blood clot in the leg)
10.  Pneumothorax
11.  Shingles
12.  Irritation of the nerves that pass through the diaphragm.
13.  Gallstones
14.   Pancreatitis
15.   Breast cancer
16.   Lung cancer
17.    esophageal cancer
18.   Colon cancer.

Diagnosis

Diagnosis includes
1. History of the patient
2.  Physical examination
3.  PET scan
4.  Chest X-ray
5.   EKG
6.    heart Stress test
7.   Endoscopy

Treatment

If the pain is due to muscle strain it can be treated through
1. Rest
2.  Ice
3.  Compression
4.  Elevation

If the pain occurs due to other reasons then the treatment options available are
1. Bone-modifying drugs
2.  Chemotherapy

Scapular fracture

It is a rare condition in which the this bone fracture.

Symptoms

1. Pain
2.  Tenderness
3.   Swelling
4.   Crepitus

Causes

1. A large amount of force
2.  Blunt trauma
3.  Crushing injuries
4.   Sport injuries
5.   Electrical shocks
6.   Seizure
7.   Cardiopulmonary resuscitation.

Scapular fracture classification

Scapular fractures are classified on the basis of regions in which the fractures occur. The classes of capsular fracture are

1. Coracoid process fractures
2.  Acromion fractures
3.   Glenoid fossa fractures.

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