There could be times when doubts arise in interpretation of history and xrays. Following entities may be considered in differentials of scapular fractures

Epiphyseal Lines
An ossification pattern of the scapula should be known to avoid this confusion. At birth, the body and spine of scapula form one ossified mass, with the coracoid, acromion, glenoid, and inferior angle all being cartilaginous.

At 3 to 18 months, a center of ossification,  appears at the mid-coracoid.

At 7 to 10 years, the coracoid base, including the upper third of the glenoid, appears.Sometimes called a subcoracoid bone and it joins the rest of the coracoid at 14 to 16 years.

An ossification center at the tip and shell-like center of the medial apex of the coracoid may appear at the same time and go on to fuse between 18 and 25 years.

Two or three acromial centers form at 14 to 16 years of age, coalesce at 19 years, and fuse to the spine between 20 and 25 years of age.

Failure of fusion with persistence of one ossification center past 25 years of age creates what is known as an os acromiale. [see below]

The glenoid fossa ossifies from four sources:

1. The coracoid base (including the upper third of the glenoid)
2. The deep portion of the coracoid process,
3. The body,
4. The lower pole

Between 8 and 13 years of age, the glenoid border may show evidence of irregular ossification.

At the inferior angle of the scapula, an ossification center appears at 15 and fuses at 20 years of age; the vertebral border center appears from 16 to 18 and fuses by 25 years of age.

The ossification centers may be asymmetric, and thus comparison films may not be helpful.

OS Acromiale
Clinically, os acromiale is the best known separate bone, resulting from failure of the adjacent ossification centers to coalesce. It can simulate an acromial fracture.

The open epiphyseal line occurs at the level of the acromioclavicular joint.

The unfused apophysis is present in 2.7% of randomly selected adults and, when present, is bilaterally symmetric in 60%.

Factors favoring the diagnosis of os acromiale over fracture are

• Bilateral occurrence
• Rounded borders with uniform space
• Bony ossification center is  even with or above the posterior acromion on the anteroposterior view.

Glenoid Hypoplasia

Hypoplasia of the glenoid may resemble and thus be misinterpreted as an impaction fracture of the glenoid.

Marked glenoid retroversion is also seen with this condition. It usually takes a benign course.

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Related posts:

1. Scapular Fractures
2. Fractures of Proximal Humerus
3. Proximal Humerus Fractures – Displaced Fractures of Tuberosity
4. Radiographic Studies In Shoulder Dislocation
5. Fractures of The Clavicle-Part II