SCAPULAR FRACTURE

[BSHC]

Introduction

Background

The primary function of the scapula is to attach the upper extremity to the thorax and provide a stabilized platform for upper extremity movement. The scapula is attached to the clavicle by the acromioclavicular and coracoclavicular ligaments and articulates with the humerus. The scapula is protected by its surrounding musculature (supraspinatus, infraspinatus, subscapularis) and its ability to move along the wall of the thorax; the body and spine of the scapula are most protected. Fractures to scapular structures typically require significant force. These factors explain the infrequent occurrence of scapular fractures.

Pathophysiology

The primary anatomic features of the scapula provide insight into the mechanisms of injury and offer a convenient classification system. Injuries to the body or the spine of the scapula typically result from a direct blow with significant force, as depicted in the image below, such as from a motor vehicle accident or a fall.

Scapular anatomy. Muscle origin and insertion.

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Scapular anatomy. Muscle origin and insertion.

Scapular fractures are caused by different mechanisms. Acromion injuries usually result from a direct downward force to the shoulder. Scapular neck fractures most frequently result from an anterior or posterior force applied to the shoulder. Glenoid rim fractures most often result from force transmitted along the humerus after a fall onto a flexed elbow. Stellate glenoid fractures usually follow a direct blow to the lateral shoulder. Finally, coracoid process fractures may result from either a direct blow to the superior aspect of the shoulder or a forceful muscular contraction that causes an avulsion fracture. Classification of these fractures is depicted below.

Classification of glenoid cavity fractures: IA - Anterior rim fracture; IB - Posterior rim fracture; II - Fracture line through the glenoid fossa exiting at the lateral border of the scapula; III - Fracture line through the glenoid fossa exiting at the superior border of the scapula; IV - Fracture line through the glenoid fossa exiting at the medial border of the scapula; VA - Combination of types II and IV; VB - Combination of types III and IV; VC - Combination of types II, III, and IV; VI - Comminuted fracture

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Classification of glenoid cavity fractures: IA - Anterior rim fracture; IB - Posterior rim fracture; II - Fracture line through the glenoid fossa exiting at the lateral border of the scapula; III - Fracture line through the glenoid fossa exiting at the superior border of the scapula; IV - Fracture line through the glenoid fossa exiting at the medial border of the scapula; VA - Combination of types II and IV; VB - Combination of types III and IV; VC - Combination of types II, III, and IV; VI - Comminuted fracture

Frequency

United States

Scapular fractures occur infrequently and account for approximately 1% of all fractures and fewer than 5% of shoulder girdle injuries.¹

Mortality/Morbidity

• Morbidity and mortality result primarily from associated injuries.
• Traditional wisdom holds that scapular fractures serve as markers of increased morbidity and mortality in patients with blunt trauma. One retrospective study comparing patients with scapular fractures due to blunt trauma with control subjects matched for age, sex, and mechanism of injury demonstrated an increase in associated thoracic injuries yet revealed no difference in mortality or neurovascular injury.²  Another study confirmed an association between scapular fractures and concomitant injuries but noted that most of the association could be explained by differences in injury severity scores.³
• A large force is usually required to fracture the scapula, particularly the body or the spine; however, suspect scapular fractures and thoroughly search for associated injuries.

Sex

Scapular fractures are more common among men than among women because of their increased incidence of significant blunt trauma.

Age

Scapular fractures predominate in persons aged 25-40 years because of the increased occurrence of significant blunt trauma in this population.

Clinical

History

The mechanisms of injury for various scapular fractures include the following:

• Body or spine fracture (40-75%): Fractures of the body or the spine of the scapula usually result from a severe direct blow, as in a fall or a motor vehicle accident.
• Acromion fracture (8-16%): Acromion fractures typically result from a downward blow to the shoulder. Superiorly displaced fractures may occur as the result of a superior dislocation of the shoulder.
• Neck fracture (5-32%): A direct anterior or posterior blow to the shoulder is the typical mechanism for a scapular neck fracture.
• Glenoid fracture (10-25%): Glenoid rim fractures often result from a fall onto a flexed elbow. A direct lateral blow is the common mechanism for a stellate fracture of the glenoid.
• Coracoid fracture (3-13%): Coracoid process fractures usually result from 1 of 2 mechanisms.
  • A coracoid process fracture is the result of a direct blow to the superior point of the shoulder or humeral head in an anterior shoulder dislocation.
  • An avulsion fracture may result from abrupt contractions of the coracoacromial muscle, short head of the biceps, or coracohumeral muscle.

Physical

Findings at physical examination may include the following:

• Body or spine fracture
  • Most common findings are tenderness, edema, and ecchymosis over the affected area.
  • The upper extremity is held in adduction, and any attempt to abduct the extremity (which results in scapular rotation) increases pain.
• Acromion fracture
  • Tenderness directly over the acromion process is the most common finding.
  • Deltoid contraction and arm abduction exacerbate pain.
  • Perform a careful neurologic examination to determine the presence of an associated brachial plexus injury.
• Neck fracture
  • A patient with a scapular neck fracture resists all movement of the shoulder and holds the extremity in adduction.
  • Maximal tenderness occurs at the lateral humeral head.
• Glenoid fracture
  • Stellate fractures of the glenoid have a presentation similar to that of scapular neck fractures, with severe pain on shoulder movement.
  • Avulsion fractures are occasionally associated with shoulder dislocations.
• Coracoid fracture
  • Patients with coracoid process fractures present with tenderness over the coracoid.
  • Forced adduction of the shoulder or flexion of the elbow exacerbates pain.

Causes

Scapular fractures are usually the result of significant blunt trauma.