Friday, September 6, 2013

Dysplasia of the shoulder, x-ray appearance

Glenoid dysplasia is a condition in which the posterior part of the glenoid bone fails to form. This has several ill effects: the load on the posterior soft tissues is increased so that the posterior labrum can fail, the humeral head displaces on the retroverted glenoid, and shoulder arthritis can develop due to abnormal loading of the remaining bone.

The MRI of the shoulder often looks like this, showing the dysplastic glenoid bone with soft tissue - presumed  cartilagenous anlage occupying the area that would normally be the posterior glenoid bone.

In the MRI below, we've labeled the bone with the white arrow and the cartilagenous anlage with the red arrow. The blue arrows point to osteophytes on the anterior and posterior humerus, indicating that degenerative arthritis has begun.

As we've emphasized before (see here), two plain x-rays are necessary and sufficient to make most diagnoses of shoulder arthritis. Below is an anteroposterior (AP) and an axillary view typical of shoulders with dysplasia. The upper view, the AP shows the under development of the inferior aspect of the glenoid.

The standardized axillary view reveals much more of the pathology: glenoid is under developed posteriorly resulting in retroversion and posterior translation of the humeral head on the glenoid.

Here are a few more images

As one might expect, surgical reconstruction of the dysplastic glenoid is difficult because of the substantial posterior bone deficiency.

Other posts on glenoid dysplasia are shown below:
Glenoid dysplasia 1
Glenoid dysplasia 2
Glenoid dysplasia 3
Glenoid dysplasia 4
Arthroplasty for dysplasia

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