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.
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.