Best Special Tests for Subacromial Impingement

Subacromial Impingement Syndrome (SAIS) is reported to be the most frequent cause of shoulder pain in an OP physical therapy clinic. Despite the high prevalence, physical therapists still struggle to appropriately diagnose the syndrome. The gold standard for diagnosing SAIS in arthroscopic surgery. Since we do not have access to this tool everyday, we must reply on our patient examination skills. A study by Michener et al, Reliability and Diagnostic Accuracy of 5 Physical Examination Tests and Combination of Tests for Subacromial Impingement, assessed 5 special tests commonly used to help rule-in SAIS. The 5 tests were Neers, Hawkins-Kennedy, Painful Arc, Empty Can (Jobe), and External Rotation Resistance Test. Specifically this article wanted to assess the interrator reliability of the tests, diagnostic accuracy of each test, and finally if clustering the tests would confirm or rule-out SAIS.


     The results of the study were surprising. Moderate to Substantial strength of agreement between raters was found for the empty can test, the painful arc sign, and external rotation resistance test. Surprisingly Hawkins Kennedy had the lowest kappa value at .39. We found this surprising because Hawkins-Kennedy is graded as painful or not painful. There seems to be little room for subjectivity, yet it received the lowest reliability among raters of all the tests. The difference likely lies in how the test is performed and thus perceived. It is easy to forget to not horizontally adduct the shoulder sufficiently or to ignore the patient's compensation of elevating the tested shoulder during IR as a means of avoiding/minimizing the pain provocation. Something we must always be wary of in studies of manual techniques is accepting the fact that all examiners perform/analyze movements the same.


     When looking at the diagnostic accuracy of each test individually, the External rotation resistance test had the highest positive likelihood ratio (LR) of 4.39, empty can had the second highest with 3.9, and the painful arc sign came in third at positive LR 2.25. Finally, the article found that when clustering the tests a "combination of any 3 positive tests out of the 5 have the best ability to confirm SAIS, with small to moderate shifts in the pretest to posttest probability."    

      While this article provides interesting and useful clinical information, the results are different from other studies in the literature. A separate article on SAIS by Park et al found that the clustering Hawkins-Kennedy, Infraspinatus Muscle Test, and the Painful Arc Sign yielded a high +LR (10.56) for ruling-in SAIS. So what cluster should you use? Personally, we would use both. The etiology of SAIS is multifactorial. Several structures have the potential to be pain generators and the presentation of SAIS will vary based on posture, scapulohumeral rhythm, accessory joint mechanics, and more. The Michener article was quick to point out the importance of a thorough subjective history to help aide in the diagnostic process.  

---

Reference: Michener LA, Walsworth MK, Doukas WC, Murphy KP. Reliability and diagnostic accuracy of 5 physical examination 
     tests and combination of tests for subacromial impingement. Arch Phys Med Rehabil. 2009 Nov;90(11):1898-903.
Park HB, Yokota A, Gill HS, El Rassi G, McFarland EG. Diagnostic accuracy of clinical tests for the different degrees 
     of subacromial impingement syndrome. J Bone Joint Surg Am. 2005 Jul;87(7):1446-55.