Responsiveness of isokinetic dynamometry parameters, pain and activity level scores to evaluate changes in patients with capsulitis of the shoulder

Objective: To determine the responsiveness to change of isokinetic dynamometry of the shoulder and to compare this responsiveness with outcome measures of pain and activity level. Design: Responsiveness was evaluated as the change in outcome after intra-articular steroid injection in patients with capsulitis of the shoulder. Effect sizes of all outcome measures, quantified as standardized response means, were compared. Relationships between change scores of shoulder function and activities were assessed. Subjects: Ten patients with unilateral capsulitis of the shoulder. Main outcome measures: Muscle strength and active range of motion were measured by isokinetic dynamometry. We then calculated involved/uninvolved ratios of the maximal peak torques of abduction, adduction, external and internal rotation, active range of motion of abduction and external rotation. In addition, pain was scored using the numeric rating scale (NRS-101) and activity level was scored using the Shoulder Disability Questionnaire. Results: The standardized response mean of all outcome parameters was equal to or greater than 0.8, except for active range of motion of abduction. No significant differences between the standardized response means were found. There is a significant correlation between the change scores of NRS-101 and Shoulder Disability Questionnaire. No significant correlations were found between the change scores of NRS-101 and Shoulder Disability Questionnaire on the one hand, and involved/uninvolved ratios of peak torques and active range of motion on the other. Conclusions: Responsiveness of all outcome measures is good. Parameters of isokinetic dynamometry may provide additional information as compared with the usual outcome measures of pain and functional level.