RESEARCH ARTICLE


Muscle Weakness in the Empty and Full Can Tests Cannot Differentiate Rotator Cuff Tear from Cervical Spondylotic Amyotrophy: Pain Provocation is a Useful Finding



Eiichiro Iwata1, *, Hideki Shigematsu1, Kazuya Inoue1, Takuya Egawa1, Yoshihiro Sakamoto2, Yasuhito Tanaka1
1 Department of Orthopedic Surgery, Nara Medical University, 840 Shijo-cho, Kashiharashi, Nara 634-8522, Japan
2 Sakamoto Orthopedic Clinic, Nara, Japan


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© 2017 Iwata et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Orthopedic Surgery, Nara Medical University, 840 Shijo-cho, Kashihara-shi, Nara 634-8522, Japan; Tel: +81-744-29-8873; Fax: +81-744-29-4902; E-mail: iwata@naramed-u.ac.jp


Abstract

Purpose:

Rotator cuff tears and cervical spondylotic amyotrophy (CSA) are often confused as the main symptom in those with difficulty in shoulder elevation. Empty and full can tests are frequently used for the clinical diagnosis of rotator cuff tears. The aim of the present study was to investigate whether the empty and full can test results can help differentiate rotator cuff tears from CSA.

Methods:

Twenty-seven consecutive patients with rotator cuff tears and 25 with CSA were enrolled. We prospectively performed empty and full can tests in patients with rotator cuff tears and CSA. The following signs were considered positive: (a) muscle weakness during the empty can test, (b) muscle weakness during the full can test, (c) pain provocation during the empty can test, and (d) pain provocation during the full can test. We calculated the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of rotator cuff tears for each positive finding.

Results:

The sensitivity and specificity of each index were as follows (sensitivity, specificity, PPV, NPV): (a) 77.8%, 0%, 45.7%, 0%; (b) 66.7%, 4.0%, 42.9%, 10.0%; (c) 88.9%, 96.0%, 96.0%, 88.9%; and (d) 74.1%, 96.0%, 95.2%, 77.4%. There were significant differences for each index.

Conclusion:

Muscle weakness during the empty and full can tests was not useful in differentiating rotator cuff tears from CSA because of low specificity and PPV. However, pain provocation was useful in differentiating these two conditions because of high specificity and PPV.

Keywords: Biceps, Rotator cuff tear, Cervical spondylotic amyotrophy, Full can test, Empty can test, Pain provocation, Muscle weakness.