PHYS THER
Vol. 86, No. 8, August 2006, p. 1076
The Bottom Line
Julie M Whitman
Julie M Whitman, PT, DSc, OCS, FAAOMPT, Assistant Professor, Department of Physical Therapy, Regis University, Denver, Colo.
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What problems did the researchers set out to study, and why?
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Various factors have been proposed to contribute to subacromial impingement syndrome (SAIS) of the shoulder, many of which (eg, abnormal acromial morphology) cannot be modified through physical therapy intervention. In this study, researchers sought to compare several factors thought to be modifiable with rehabilitation in people with and without SAIS. These factors included kinematics of the scapula, shoulder range of motion, shoulder muscle force, and both upper thoracic spine and shoulder resting posture.
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Who participated in the study?
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Forty-five subjects with impingement syndrome (SAIS group) and 45 matched subjects without known shoulder pathology or impairment (control group). Subjects were matched by age, sex, and hand dominance.
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What new information does this study offer?
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Many researchers have studied the scapular kinematics in patients with SAIS, but results of these studies to date have been largely variable. The results of previous studies may be limited, however, because often control subjects were included who were not matched to the subjects with SAIS, or because the studies compared shoulder motion of the affected shoulder to the asymptomatic side only. In addition, prior studies of scapular kinematics typically have not examined the shoulder for other potential concomitant impairments, such as abnormal isometric force production, range of motion, or spinal or scapular posture. The current study included a matched control group as well as measurements of several physical characteristics of patients with SAIS.
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How did the researchers go about the study?
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All subjects were examined with the following tests and measures: (1) goniometric measurement of shoulder range of motion, (2) assessment of upper thoracic spine and scapular resting posture, (3) measurement of shoulder isometric muscle force with a handheld dynamometer, and (4) assessment of shoulder kinematics with an electromagnetic motion analysis system during 3 active shoulder motions (shoulder flexion, scapular plane elevation, and external rotation at 90 degrees of abduction).
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What did the researchers find?
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There were no differences in resting posture between the subjects with and without SAIS. The SAIS group demonstrated less range of motion of the shoulder in all directions assessed, and less isometric muscle force for shoulder external rotation and scapular plane elevation. Finally, subjects with SAIS demonstrated slightly greater upward rotation of the scapula and elevation of the clavicle with shoulder flexion and slightly more posterior tilt and retraction of the clavicle with scapular plane elevation compared with those who did not have SAIS.
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How might the results of this study apply to patients who are treated by physical therapists from this point forward?
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As the authors theorize, the limited mobility and decreased shoulder muscle force identified in the SAIS group may support the use of interventions designed to improve shoulder strength and mobility. In addition, the authors propose that the kinematic differences identified between the two groups of subjects may represent compensatory scapulothoracic movement strategies, possibly as a result of weakness of the shoulder musculature or loss of mobility of the shoulder. Although the potential clinical implications of these small kinematic differences between groups are yet to be determined, identification of these findings could possibly lead clinicians to address impairments in strength, range of motion, or motor control that are hypothesized to contribute to the altered kinematics of the shoulder girdle.
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What are the limitations of the study, and what further research is needed?
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Several limitations can be identified in this study. First, all measurements of range of motion, muscle force, and kinematics were performed by a single examiner who was not blind to group assignment, which could lead to examiner bias. Second, the average differences between groups for the kinematic measures were small, ranging from 2.9 to 3.8 degrees. These small differences might not be detectable in a standard clinical environment—and might not be clinically relevant. Further research is needed to determine whether a management strategy that specifically addresses the identified impairments of reduced muscle force, range of motion, and altered kinematics results in greater improvements in pain, activity, and participation than competing non-invasive management strategies.
[McClure PW, Michener LA, Karduna AR. Shoulder function and 3-dimensional scapular kinematics in people with and without shoulder impingement syndrome. Phys Ther. 2006;86:1075–1090.]
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Related Article
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Shoulder Function and 3-Dimensional Scapular Kinematics in People With and Without Shoulder Impingement Syndrome
- Philip W McClure, Lori A Michener, and Andrew R Karduna
Physical Therapy 2006 86: 1075-1090.
[Abstract]
[Full Text]
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Copyright © 2006 by the American Physical Therapy Association.
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