Impingement / Instability Differentiation

Purpose

The purpose of this article is to help healthcare providers differentiate between shoulder impingement and instability by utilizing the most current literature.

Impingement

Individual special tests for sub-acromial impingement have varying psychometric properties. For this reason, it is best to utilize special test clusters in order to diagnose this injury. Two special test clusters are provided below that can be used in order to diagnose sub-acromial impingement[1].



Sensitivity Specificity Accuracy% PPV% NPV%
Hawkins-Kennedy .92 .25 72.8 75.2 56.2
Neers .89 .31 72.0 75.9 52.3
Horizontal-adduction .82 .28 66.4 73.7 38.4
Speed .69 .56 64.8 79.2 41.6
Yergason .37 .86 51.2 86.8 35.6
Painful arc .33 .81 46.4 80.5 32.5
Drop arm .08 .97 33.6 87.5 29.9









A total of 5 positive special tests is indicative for subacromial impingement[1].

Positive tests Sensitivity Specificity Accuracy% PPV% NPV%
All positive .04 .97 31.2 80.0 29.1
≥6 positive .30 .89 47.2 87.0 34.0
≥5 positive .38 .86 52.0 87.1 36.0
≥4 positive .70 .67 68.8 83.7 47.0
≥3 positive .84 .44 72.8 72.8 44.4

Accuracy: The percentage of time that the result of the test reflects the true nature of the condition

A second cluster utilizes a slightly different set of special tests[2].


Sensitivity Specificity Positive LR Negative LR
Hawkins-Kennedy .63 .62 1.63 .61
Neers .81 .54 1.17 .35
Painful arc .75 .67 2.25 .38
Empty can .50 .87 3.90 .57
External rotation resistance .56 .87 4.39 .50

Any combination of 3 or more positive tests are indicative of sub-acromial impingement[2]


Sensitivity Specificity Positive LR Negative LR
3+ positive tests .75 .74 2.93 .34

Instability

Test Sensitivity Specificity +LR -LR
Apprehension test .72 .96 20.2 .29
Relocation test .81 .92 10.4 .20
Anterior drawer test .53 .85 3.57 .56

Instability can be categorized in a few different ways, including anterior, posterior and multidirectional instability. The 3 tests above focus on the diagnosis for anterior shoulder instability[3].

Positive tests Sensitivity Specificity +LR -LR
Apprehension, relocation and anterior drawer tests .48 .99 39.1 .52
Apprehension and relocation tests .81 .98 39.7 .19
Relocation and anterior drawer tests .48 .96 18.0 .54
Apprehension and anterior drawer tests .46 .98 23.1 .55


The above table represents a cluster to help rule in favor of an anterior shoulder instability diagnosis[3]. With positive results of any 2 tests or more, you can be fairly confident ruling in favor of anterior shoulder instability. It should be noted that the apprehension test is only positive in the presence of apprehension and the relocation test is considered positive with the relief of apprehension. In addition, the anterior drawer test is positive when symptoms of instability are reproduced.

The tests below[4][5] are additional diagnostic tests for instability which may assist you in your examination, however they are not a part of the above mentioned cluster.


Sensitivity Specificity +LR -LR
Anterior release test .92 .89 8.6 .09



Sensitivity Specificity +LR -LR
Sulcus Sign .17 .93 2.43 .89


+LR: describes how much the odds of impingement increase with a positive test
-LR: describes how much the odds of impingement decrease with a negative test

Recent Related Research (from Pubmed)

References

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  1. 1.0 1.1 Caliş M, Akgün K, Birtane M, Karacan I, Caliş H, Tüzün F. Diagnostic values of clinical diagnostic tests in subacromial impingement syndrome. Ann Rheum Dis. 2000 Jan;59(1):44-7.
  2. 2.0 2.1 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.
  3. 3.0 3.1 Farber AJ, Castillo R, Clough, M, et. al. Clinical assessment of three common tests for traumatic anterior shoulder instability. J Bone Joint Surg Am. 2006;88:1467-1474.
  4. Gross ML & Distefano MC. Anterior release test. A new test for occult shoulder instability. Clin Orthop Relat Res. 1997;339:105-108.
  5. Nakagawa S, Yoneda M, Hayashida K, et. al. Forced shoulder abduction and elbow flexion test: a new simple clinical test to detect superior labral injury in the throwing shoulder. J Arthr Relat Surg. 2005;21:1290-1295.