Three Tests for Diagnosing Complete Rupture of the Rotator CuffResearchers are trying to find ways to detect full-thickness tears of the rotator cuff without the expense and invasiveness of an arthroscopic exam. To do this, they are comparing the results of clinical tests with ultrasound results. The advantage of the ultrasound is that both shoulders can be viewed. This gives a side-to-side comparison that isn't possible with standard arthroscopy.
In this study, the accuracy of three specific tests called the lag signs are studied. These include the external rotation lag sign, the drop sign, and the internal rotation lag sign.
Each procedure specifically tests one or more of the four tendons of the rotator cuff. The authors described each test in detail. All three tests were performed on 46 painful shoulders in 37 patients. Right after the clinical testing, diagnostic ultrasound tests were done on both sides.
The results showed that there isn't one single test that can accurately diagnose a rotator cuff tear. The rotator cuff tendons are not easily isolated. They come together closely and insert around the shoulder. A negative test doesn't necessarily mean the patient doesn't have a full-thickness tear. And a positive test result doesn't always mean there is a full-thickness tear.
The bottom-line is that clinical lag tests can't be relied upon. This is especially true in the older groups who often have full-thickness rotator cuff tears without any symptoms. Many people with painless tears have normal function. It's only when pain enters the picture that the condition becomes a problem.
Advanced imaging using either ultrasound or arthroscopy is still the most reliable diagnostic methods. Ultrasound has the added advantage over arthroscopy of providing comparisons from side to side.
Caroline A. Miller, MSc, et al. The Validity of the Lag Signs in Diagnosing Full-Thickness Tears of the Rotator Cuff: A Preliminary Investigation. In Archives of Physical Medicine and Rehabiliation. June 2008. Vol. 89. No. 6. Pp. 1162-1168.
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