Shoulder Impingement Syndrome: Diagnosis [Clinical Review Discussion]

The gleno-humeral joint is commonly accepted to be the most complex joint in the human body. Possibly due to the difficulty of arriving at an accurate diagnosis, the term "shoulder impingement syndrome" (SIS) has become a standard term in shoulder diagnosis. Any condition that narrows the space between the anterior/inferior aspect of the acromion and coracoacromial ligament can result in SIS (1). The most common causative factors are a thickened subacromial bursa and rotator cuff tendonopathy.

According to Ostor et al there are no universally recognized tests to evaluate the upper limb and at least 20 tests are available to assess rotator cuff pathologies alone (2). Most tests have only been researched in a very limited number of studies which makes evaluation difficult. Of a myriad of tests, this monograph will attempt to identify those with the highest degree of validity and reproducibility.

Unfortunately de Winter et al and Ostor et al, in studies of 201 and 136 patients respectively, found only "fair" to "moderate" interexaminer reliability for several different SIS tests (2;3).

Most clinical tests for SIS have either high sensitivity and low specificity or high specificity and low sensitivity. This confounds their value as diagnostic tools. To fully understand the relative values of these tests it is important for the reader to understand specificity and sensitivity. High sensitivity means a negative test rules out the diagnosis. A convenient pneumonic device is SnNout (sensitivity negative rules out). High specificity means a positive test rules in the diagnosis. The pneumonic is SpPin (specificity positive rules in). A test with high specificity and low sensitivity means if the test is positive you can comfortably make the diagnosis but cannot rule out the diagnosis if the test is negative. If the test has high sensitivity and low specificity, a negative test allows you to rule out the diagnosis but a positive test does not rule in the diagnosis.

The sensitivities and specificities reported below were established using findings on surgical intervention, MRI or the injection test as the gold standard.

Adding to the difficulty of arriving at an accurate diagnosis is the finding that high pain, bilateral involvement and chronicity degrade accuracy of many tests (3).