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Shoulder Strength in Asymptomatic Individuals with Intact Compared with Torn Rotator Cuffs
H. Mike Kim, MD1; Sharlene A. Teefey, MD1; Ari Zelig, BA1; Leesa M. Galatz, MD1; Jay D. Keener, MD1; Ken Yamaguchi, MD1
1 Department of Orthopaedic Surgery, Washington University School of Medicine, One Barnes-Jewish Hospital Plaza, 11300 West Pavilion, Campus Box 8233, St. Louis, MO 63110
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Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from the National Institutes of Health (R01 AR051026-01A1). Neither they nor a member of their immediate families received 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, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
A commentary is available with the electronic versions of this article, on our web site (www.jbjs.org) and on our quarterly CD-ROM/DVD (call our subscription department, at 781-449-9780, to order the CD-ROM or DVD).
Investigation performed at the Department of Orthopaedic Surgery, Barnes-Jewish Hospital, Washington University School of Medicine, St. Louis, Missouri

The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2009 Feb 01;91(2):289-296. doi: 10.2106/JBJS.H.00219
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Abstract

Background: Normative data are essential to the evaluation of shoulder function. The purposes of this study were to establish a normative database of isometric shoulder strength measured in asymptomatic individuals verified to have intact rotator cuffs and to determine the effect of asymptomatic rotator cuff tears on shoulder strength.

Methods: Two hundred and thirty-seven volunteers with no shoulder pain or history of shoulder injury were screened with ultrasonography bilaterally for rotator cuff tears and then underwent isometric strength measurements for abduction in the scapular plane and external rotation. Statistical analysis was performed to evaluate the effect of age, body habitus, hand dominance, and the presence of a rotator cuff tear on shoulder strength.

Results: Of the 237 volunteers, forty-one were found to have a torn rotator cuff in at least one shoulder. The prevalence of rotator cuff tears was 0% for the subjects between forty and forty-nine years old; 10%, between fifty and fifty-nine years old; 20%, between sixty and sixty-nine years old; and 40.7% for those seventy years old or older. Both abduction strength and external rotation strength in the male subjects showed an age-dependent decrease, whereas only abduction strength showed an age-dependent decrease in the female subjects. In multiple regression analysis, age and weight were the most important predictors of abduction strength and external rotation strength, respectively. In the shoulders with a large-to-massive full-thickness rotator cuff tear, abduction strength was significantly decreased (p = 0.007). Additionally, the ratio of abduction strength to external rotation strength was significantly decreased in the shoulders with a large-to-massive full-thickness tear compared with the shoulders with an intact rotator cuff (p < 0.001).

Conclusions: There is a high prevalence of rotator cuff tears in elderly asymptomatic individuals. Asymptomatic shoulders with a large-to-massive full-thickness rotator cuff tear have significantly decreased abduction strength. When there is a substantial decrease in abduction strength in relation to external rotation strength, the presence of an asymptomatic full-thickness tear should be suspected in that shoulder. Previous studies establishing normative values for isometric shoulder strength may have been skewed by the presence of asymptomatic rotator cuff tears in elderly subgroups.

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    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Jerrold M. Gorski, MD
    Posted on February 11, 2009
    Is the Asymptomatic Shoulder Asymptomatic?
    Winthrop University Hospital, Mineola, NY

    To the Editor:

    I was encouraged to write after reading the final question posed by Dr Cofield in his JBJS web Commentary on the article by Kim et al. (1) "I would pose a final philosophical question: Is a person who has a painless rotator cuff tear that is causing weakness really asymptomatic"?

    The answer to this pointed question, I believe, lies beyond both philosophy and the simple confusion of symptoms and physical findings. I have observed that the asymptomatic shoulder commonly presents as symptomatic "neck" pain (2, 3). My hope is that further research will prove that the asymptomatic shoulder underlies some chronic neck pain syndromes in which evidence is lacking like whiplash, trapezius spasm, trigger points, fibromyalgia, and thoracic outlet syndrome. I am hopeful that the normative data established by these authors will help their ongoing scientific analysis of the mysterious and highly prevalent asymptomatic shoulder. I hope they address two additional questions in future reports: why does the rotator cuff tear with presumably decreasing usage with age and why is the shoulder asymptomatic?

    The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received 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, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

    References

    1. Kim HM, Teefey SA, Zelig A, Galatz LM, Keener JD, Yamaguchi K. Shoulder Strength in Asymptomatic Individuals with Intact Compared with Torn Rotator Cuffs. J Bone Joint Surg Am 2009;91:289-296 2. Gorski JM, Schwartz H. Shoulder Impingement Presenting as Neck Pain. J Bone Joint Surg 85-American 2003;4:635-638.

    3. Gorski JM. A New Pain in the Neck. Bulletin of the AAOS, Aug, 2007 27-29.

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