In the last two decades, subacromial impingement syndrome has become an increasingly common diagnosis for patients who have a painful shoulder. However, subacromial impingement syndrome is a specific diagnosis and is not the only cause of pain in the anterosuperior aspect of the shoulder. Impingement may be difficult to diagnose because the clinical presentation may be confusing. It is important to differentiate subacromial impingement syndrome from other conditions that may cause symptoms in the shoulder, such as glenohumeral instability, cervical radiculitis, calcific tendinitis, adhesive capsulitis, degenerative joint disease, isolated acromioclavicular osteoarthrosis, and nerve compression. This is particularly true when examining younger patients, especially athletes who perform overhead motions with use of the upper extremity, in whom the diagnosis of impingement should be made with caution. In many cases, the primary diagnosis is subtle glenohumeral instability even though impingement and subacromial bursitis are evident.
In the past, many authors noted abnormal contact between the coracoacromial arch and the rotator cuff tendons6,18,23,63,66,71-73, but the exact etiology was not clearly understood. Meyer66, in 1931, proposed that tears of the rotator cuff occurred secondary to attrition as a result of friction with the undersurface of the acromion. He described corresponding lesions on the undersurface of the acromion and the greater tuberosity, although he did not implicate the acromion directly. Codman18, in 1934, defined the critical zone, where most degenerative changes occur, as a portion of the rotator cuff located one centimeter medial to the insertion of the supraspinatus on the greater tuberosity. Armstrong6, in 1949, introduced the term supraspinatus syndrome and proposed that the condition should be treated with a total acromionectomy. Diamond23 also noted the role of the acromion as a cause …
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