Sunday, November 30, 2014

Posterior head subluxation in arthritic shoulders

Importance of a three-dimensional measure of humeral head subluxation in osteoarthritic shoulders.

These authors analyzed 112 computed tomography scans of osteoarthritic shoulders, including measures of glenohumeral subluxation, scapulohumeral subluxation, and glenoid version in 3D relative to the scapular plane and the scapular axis.

Orientation of the humeral subluxation was rarely within the arbitrary computed tomography plane leading the authors to conclude that it should be measured in 3D to detect out-of-plane subluxation

Scapulohumeral subluxation and glenoid version were highly correlated in amplitude and in orientation. Approximately every degree of glenoid version induced 1% of scapulohumeral subluxation in the same orientation of the version. Glenohumeral subluxation was not correlated with glenoid version.

Comment: Interested readers should visit this related post

The key point is that CT scans, whether 2-D or 3-D, are done with the arm at the side of the patient and, therefore, not represent the glenohumeral and scapulohumeral relationships with the arm in functional positions. See this post on functional decentering.

We prefer to measure posterior humeral subluxation an standardized axillary views with the arm in the functional position of 60 degrees of elevation in the plane of the scapula as shown here.


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