Spine of the scapula and spinoacromial fractures
General considerations
Fractures of the spine of the scapula and spinoacromial fractures are the most common scapular process fractures.
The spine of the scapula and the acromion are the bony origin of the posterior, middle, and part of the anterior third of the deltoid muscle.
Etiology
Fractures through the spine of scapula and spinoacromial fractures can be caused by:
- Direct trauma on the posterolateral aspect of the shoulder
- Deltoid tension in reverse total shoulder replacement
- The superior screw of the metaglene which may weaken the base of the spine of scapula
Pitfall: It is important to distinguish traumatic fractures of the body of the acromion from os acromiale. Os acromiale is a common finding in rotator cuff care arthropathy for which reverse total shoulder replacement is often performed. Os acromiale is frequently asymptomatic and may not have a functional significance. A fracture of the acromion is always symptomatic and nearly always has a functional consequence.
Clinical signs
- Pain over the posterosuperior aspect of the shoulder
- Weakness in all directions of shoulder motion
- There may be a palpable gap over the spine of the acromion
- Visible deformity if displaced
- The shoulder may rest in a protracted posture
Imaging
- Lateral and scapular Y x-rays may show the fracture
- CT scan is the definitive imaging
Pearl: The preoperative x-rays and CT scans will show an os acromiale if present and help to distinguish this from an intraoperative or postoperative acromial fracture.
