Copyright © 2009 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Robert H. Cofield, MD*,
Mayo Clinic, Rochester, Minnesota
Posted February 2009
Kim et al. have performed a study that is very well
formulated and uses correct scientific methodology. The subjects who
participated in the study were, interestingly, mostly family members who
accompanied patients to the orthopaedic clinic and, to a much lesser degree, volunteers
or patients who visited the orthopaedic clinic for the treatment of
non-shoulder-related problems. The age and sex parameters were very well
dispersed. Racial parameters were not. The subjects (219 Caucasians, seven
African Americans, and eleven Asians) were predominantly white, and therefore
the conclusions are not generalized to other ethnic groups.
There is no question that during physical examination it is
very useful to know what is normal and what is not; thus, one strength of this
study is the information that the authors provide with regard to normative
values for isometric shoulder strength. The second strength of this study is
that it offers a reassessment of how many asymptomatic individuals may actually
have unsuspected rotator cuff tearing. The outcome was interesting: no subjects
who were in their forties had tearing; 10% of subjects who were in their fifties
had tearing; 20% of subjects who were in their sixties had tearing; and
approximately 41% of subjects who were seventy years of age or older had
tearing. Thus, tearing developed with increasing age in a substantial number of
asymptomatic individuals, but often at a lesser rate than reported in some
earlier studies1-3.
The following is a list of some important conclusions that
readers may glean from this study: men are stronger than women; there is no
difference in shoulder strength between the dominant and nondominant sides in
men, but there is a slight difference in women; strength decreases with age; those
with greater weight are stronger; when there is a large to massive
full-thickness tear, abduction strength is significantly decreased (p = 0.007) compared
with the strength in the contralateral shoulder with an intact rotator cuff or
a smaller amount of tearing; and finally, clinical strength measurements may
not detect a tear in a patient who has a small amount of rotator cuff tearing.
The authors are to be commended for addressing so much
attention to the details of the study. They have confirmed the hypothesis that
asymptomatic rotator cuff tears develop with age but they have shown that these
tears are not as frequent as some studies have suggested in the past1-3.
They have demonstrated that simple parameters of age, sex, weight, and hand
dominance influence the values obtained on physical examination. To reiterate
an important point, if one has a smaller rotator cuff tear, physical
examination may well not identify it on the basis of strength testing alone. I
would pose a final philosophical question: Is a person who has a painless rotator
cuff tear that is causing weakness really 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.
References
1. Milgrom C, Schaffler M, Gilbert S, van Holsbeeck M. Rotator-cuff changes in asymptomatic adults. The effect of age, hand dominance and gender. J Bone Joint Surg Br. 1995;77:296-8.
2. Sher JS, Uribe JW, Posada A, Murphy BJ, Zlatkin MB. Abnormal findings on magnetic resonance images of asymptomatic shoulders. J Bone Joint Surg Am. 1995;77:10-5.
3. Tempelhof S, Rupp S, Seil R. Age-related prevalence of rotator cuff tears in asymptomatic shoulders. J Shoulder Elbow Surg. 1999;8:296-9.
|
