Commentary & Perspective

Commentary & Perspective on
"Diagnostic Accuracy of Clinical Tests for the Different Degrees of Subacromial Impingement Syndrome"
by Hyung Bin Park, MD, et al.

Commentary & Perspective by
Robert H. Cofield, MD*,
Mayo Clinic, Rochester, Minnesota

It has often been said, and it is generally recognized to be true, that the impingement syndrome represents a clinical diagnosis. However, the advent of magnetic resonance imaging allows us to analyze structural changes in more detail and offers an important adjunct to the clinical decision-making process as it relates to the various stages of the impingement syndrome.

A number of physical examination signs have been described as being helpful in clinical decision-making as it relates to the diagnosis of shoulder impingement. The value of these signs is often called into question as clinicians recognize that some patients who seem to have an impingement problem do not have positive signs while other patients who clearly have a problem other than impingement do have positive signs. Park et al. pointed out to us the great spectrum of changes seen in the impingement complex, including bursal inflammatory changes, partial-thickness rotator cuff tearing, and full-thickness rotator cuff tearing. These authors wondered whether there was some variability of usefulness for the various clinical signs in these different stages and evaluated eight different physical examination tests. This is a daunting undertaking, and I think we can all appreciate how we can become easily confused by this interplay of so many variables as we try to understand this problem and, indeed, this paper.

The various tests are probably best understood by considering the Neer impingement sign, the Hawkins-Kennedy impingement sign, and the cross-body adduction test as representing irritability of the periarticular soft tissues at the extremes of movement and by considering the painful arc sign and the drop-arm sign as representing soreness of these tissues in more of a central arc of movement, sometimes associated with some degree of weakness. The other three tests—the supraspinatus muscle strength test, the infraspinatus muscle strength test, and the Speed test—assess irritability of the muscles in contraction against resistance and can also indicate a degree of weakness.

Thankfully, conventional wisdom was often reinforced during this analysis, with the best clinical test for bursitis being the Neer impingement sign, the best clinical test for partial-thickness rotator cuff tearing being the Neer impingement sign, and the best tests for full-thickness rotator cuff tearing being the painful arc sign, the drop-arm sign, and the infraspinatus muscle strength test.

The authors argue, and I think convincingly so, that using a combination of tests will increase diagnostic accuracy, with the Neer sign, the Hawkins-Kennedy impingement sign, and the painful arc sign being quite sensitive for bursitis and reasonably sensitive for partial-thickness rotator cuff tearing. The Hawkins-Kennedy impingement sign and the painful arc sign continue to be rather sensitive for full-thickness rotator cuff tearing, with the muscle tests becoming more often positive in the presence of full-thickness rotator cuff tearing.

The authors remind us and detail for us mathematically that these tests are more often sensitive than they are specific. They remind us that physical examination testing tends to be less reproducible and reliable, although that was not a focus of this manuscript. They also remind us that there are other physical examination signs that can be used, such as analysis for subacromial crepitation, local tenderness, and various lag signs and variants thereof.

This very complex analysis helps us to further our understanding of the issues surrounding shoulder impingement and indirectly makes us aware of the extreme variability of structural changes that can occur with a rather similar clinical presentation. As physicians and surgeons interested in musculoskeletal injury and diseases, we all really focus on identifying structural changes and study the various means with which they can be effectively treated for the patients' benefit. The less advanced aspects of the impingement syndrome thus present an ongoing problem for us in so far as diagnosis is concerned. The new tools available for us—magnetic resonance imaging and arthroscopy—are expensive or invasive, and it is of great assistance to us to have more information about the utility of rather simple physical examination methods.

*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

Copyright © 2005 by the The Journal of Bone and Joint Surgery, Inc.