Understanding the arthritic shoulder and planning its management depends in large part on determining the anteroposterior position of the humeral head on the glenoid in a position of function.
Documenting the effectiveness of surgical management of the arthritic shoulder depends in large part on determining the postoperative anteroposterior position of the humeral head on the glenoid using the same method that was used preoperatively.
As explained in this video, these goals can most practically be accomplished by obtaining the axillary "truth" view taken with the arm forwardly elevated in a position of function. A proper axillary "truth" view will show the "eye" of the spinoglenoid notch (see arrow).
The axillary "truth" view can reveal the wide range of posterior decentering encountered in clinical practice as shown here (note the "eye" on each of these views):
Quantitating the amount of posterior decentering is easily measured on a properly taken axillary "truth" view using 6 straightforward steps:
1. A line segment (AC) is drawn from the anterior (A) to the posterior (C) edges of the glenoid.
2. A perpendicular bisector to this line is drawn from the midpoint (B) of AC.
3. X is the center of a circle fit to the humeral articular surface
4. A diameter of the circle (DF) is drawn through X and parallel to AC
5. E is the intersection of DF with the perpendicular bisector drawn from B.
6. The percentage of posterior decentering is (EF/DF – 0.5) × 100%.
This particular shoulder demonstrates a preoperative posterior decentering of 24%.
Unfortunately, many axillary views are not "truth" views, see such an example below. Functional decentering cannot be measured on such a view.
Unfortunately, decentering in a position of function cannot be measured on a CT scan obtained with the arm at the side (see below):
The amount of decentering preoperatively in a position of function can be compared before and after surgery using the axillary "truth" view.
Examples of the utility of the axillary "truth" view can be seen in "Management of intraoperative posterior decentering in shoulder arthroplasty using anteriorly eccentric humeral head components" and in "Total shoulder arthroplasty with an anterior-offset humeral head in patients with a B2 glenoid"
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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link).
The total shoulder arthroplasty (see this link).
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link).
Shoulder rehabilitation exercises (see this link).
