Scapula Fractures

EPIDEMIOLOGY

This relatively uncommon injury represents 3% to 5% of shoulder fractures and 0.4% to 1% of all fractures.
The mean age of patients who sustain a scapula fracture is 35 to 45 years.

ANATOMY

This flat, triangular bone links the upper extremity to the axial skeleton.
Protection from impact is provided by the large surrounding muscle mass as well as the mobility of the scapula on the chest wall, which aids in force dissipation.

MECHANISM OF INJURY

Injury is usually the result of high-energy trauma.
- Motor vehicle accident in approximately 50% of cases and motorcycle accident in 11% to 25%
Indirect injury occurs through axial loading on the outstretched arm (scapular neck, glenoid, intra-articular fracture).
Direct trauma occurs from a blow or fall (scapula body fracture) or through direct trauma to the point of the shoulder (acromion, coracoid fracture).
Shoulder dislocation may cause a glenoid fracture.
Muscles or ligaments may cause an avulsion fracture.

ASSOCIATED INJURIES

CLINICAL EVALUATION

A full trauma evaluation is essential, with attention to airway, breathing, circulation, disability, and exposure.
The patient typically presents with the upper extremity supported by the contralateral hand in an adducted and immobile position, with painful range of motion, especially shoulder abduction.
A careful examination for associated injures should be performed, with a thorough neurovascular assessment.
Compartment syndrome overlying the scapula is uncommon, but it must be ruled out in the presence of pain out of proportion to the apparent injury. Comolli sign is triangular swelling of the posterior thorax overlying the scapula and is suggestive of hematoma resulting in increased compartment pressures.

RADIOGRAPHIC EVALUATION

May first be picked up on a chest x-ray. Initial radiographs should include a trauma series of the shoulder, consisting of a true anteroposterior view, an axillary view, and a scapular-Y view (true scapular lateral); these generally are able to demonstrate most glenoid, scapular neck, body, and acromion fractures.
- The axillary view may be used to further delineate acromial and glenoid rim fractures.
- An acromial fracture should not be confused with an os acromiale, which is a rounded, unfused apophysis present in approximately 3% of the population. When present, it is bilateral in 60% of cases.
- Glenoid hypoplasia, or scapular neck dysplasia, is an unusual abnormality that may resemble glenoid impaction and may be associated with humeral head or acromial abnormalities. It has a benign course and is usually noted incidentally.
A 45-degree cephalic tilt (Stryker notch) radiograph is helpful to identify coracoid fractures.
Computed tomography may be useful for further characterizing intra-articular glenoid fractures.
Because of the high incidence of associated injuries, especially to thoracic structures, a chest radiograph is an essential part of the evaluation.