The critical shoulder angle (CSA) is the angle between the line connecting the superior border with the inferior border of the glenoid and the line connecting the most lateral point of the acromion with the inferior border of the glenoid on a true anteroposterior (AP) radiograph. High CSAs (> 35°) have been associated with rotator cuff tears, whereas low CSAs (< 30°) have been associated with glenohumeral osteoarthritis.
These authors state that acromioplasty has been proposed as a means of altering elevated critical shoulder angles (CSAs). In cadavers, they considered the effect of a virtual acromioplasty of 2.5 and 5 mm in specimens with a CSA greater than 35°.
Using a "critical acromial point" they found that 2.5-mm acromial resection failed to reduce the CSA to 35° or less in 7 of 13 shoulders, whereas a 5-mm resection reduced the CSA to 35° or less in 12 of 13. They suggest that these data can guide surgeons in where and how to alter the CSA if future studies demonstrate a clinical benefit to surgically modifying this radiographic parameter.
Comment: This study brings up a number of interesting questions:
(1) is the relationship between observed CSA and cuff disease one of cause and effect or just one of association? In other words, does cuff disease change the CSA, does a certain CSA cause cuff disease, or are cuff disease and CSA each the result of the patient's genetics. Demonstrating causation is tricky business as pointed out by Hill at al who showed the causation of scrotal cancer in chimney sweeps. They developed nine criteria:
•Strength of association •Consistency of association
•Specificity of the association
•Temporal relationship of the association
•Dose response of the effect
•Biological plausibility
•Coherence
•Experimental evidence
•Analogy
To see these criteria in action, see Published Evidence Demonstrating the Causation of Glenohumeral Chondrolysis by Postoperative Infusion of Local Anesthetic Via a Pain Pump.
(2) if an increased CSA is related to cuff pathology, is it reasonable to think that modifying the CSA will change the natural history of cuff disease. As one wag said, "does the fact that wide set eyes are associated with higher IQ (see this link), suggest that facial surgery will alter intelligence"?
(3) If the CSA is surgically reduced, will this make the shoulder more at risk for osteoarthritis (a condition that has been associated with lower CSA)?
(4) What are the downsides of acromioplasty in terms of loss of deltoid origin and loss of the superior stability of the coracoacromial arch?
J===
The reader may also be interested in these posts:
Information about shoulder exercises can be found at this link.
Use the "Search" box to the right to find other topics of interest to you.
You may be interested in some of our most visited web pages including: shoulder exercises, shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials' See from which cities our patients come.
