- Author: Joseph C Schmidt, MD; Chief Editor: Trevor John Mills, MD, MPH more...
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.
Scapular fractures can be divided by location :
Body (spine) fractures
Scapula fractures have been found to be associated with the following :
Fractures of the acromion are generally caused by a significant blunt force to the shoulder that is directed anteriorly. Fractures of the glenoid neck often occur as the result of falling on an outstretched arm, as well as blunt force, and may be associated with humerus fractures or shoulder dislocation.
Glenoid fractures may occur from a direct lateral blow to the shoulder or a force transmitted from the humerus, such as falling on the elbow. Glenoid fossa fractures constitute about 50% of scapular fractures, and glenoid rim fractures about 7% of all scapular fractures.
Up to 90% of scapular fractures are nondisplaced. Most scapular fractures will heal within 6 weeks, but it may take months before full functional recovery is achieved.
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 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.
The AO Foundation and Orthopaedic Trauma Association also developed a comprehensive system for in-depth classification of scapular fractures for clinical research and surgical decision making.[2, 3]
Scapular fractures occur infrequently and account for approximately 1% of all fractures and 3% to 5% of shoulder girdle injuries.[4, 5]
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. 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.
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.
Scapular fractures are more common among men than among women because of their increased incidence of significant blunt trauma. Scapular fractures predominate in persons aged 25-40 years because of the increased occurrence of significant blunt trauma in this population.
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