These authors used 3D CT scans to make three dimensional measurements of glenohumeral and scapulohumeral subluxation and to evaluate the association of subluxation with the glenoid version in 112 shoulders with osteoarthritis.
They found that the direction of subluxation and glenoid version varied widely. Subluxation of the humeral head relative to the scapular plane and glenoid version relative to the scapular plane were highly correlated in amplitude and in direction. Approximately every degree of glenoid version induced 1% of scapulohumeral subluxation in the same orientation of the version.
However, subluxation of the humeral head with respect to the glenoid was not correlated to glenoid version in 2D or in 3D.
It was interesting to note that while the predominant direction of glenohumeral subluxations were posterior, many were either in the posterior-superior or posterior-inferior sector.The scapulohumeral subluxations were primarily posterior and posterior-superior. The glenoid version was primarily posterior and posterior-superior.
Comment: These results are related to those discussed in a prior post. The variable direction of glenoid version and humeral subluxation is also to be compared with the findings of another recent study as well.
Of course the issue with measuring subluxation with 2D or 3D CT scans is that at the time of the CT, the arm is resting at the side, rather than being in a functional position. A clinically more important assessment of humeral subluxation can be obtained from an axillary view taken with the am in the functional position of 90 of elevation in the plane of the scapula = the 'truth view'. Rather than using expensive CT technology, the amount of subluxation can be evaluated on the axillary view using the point of glenohumeral contact - it's simpler, reproducible, less expensive, and does not require the radiation of a CT scan. In most cases, we have not found that CT scans add clinically useful information to what we can obtain from standardized radiographic views.
Of course the issue with measuring subluxation with 2D or 3D CT scans is that at the time of the CT, the arm is resting at the side, rather than being in a functional position. A clinically more important assessment of humeral subluxation can be obtained from an axillary view taken with the am in the functional position of 90 of elevation in the plane of the scapula = the 'truth view'. Rather than using expensive CT technology, the amount of subluxation can be evaluated on the axillary view using the point of glenohumeral contact - it's simpler, reproducible, less expensive, and does not require the radiation of a CT scan. In most cases, we have not found that CT scans add clinically useful information to what we can obtain from standardized radiographic views.
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