The relationship among strength and mobility measures and self-report outcome scores in persons after rotator cuff repair surgery: Impairment measures are not enough

In the past, measures of active range of motion and strength testing were deemed sufficient to "prove" the efficacy of treatment interventions. In the current outcomes milieu, however, the focus has shifted to patient-centered assessment (ie, patients' ability to perform activities that are personally relevant). We report results from a study with patients in the private practice of a shoulder surgeon. In this study we evaluated the relationship between impairment measures and scores from several shoulder outcome scales. In addition, we examined transcripts of interviews with shoulder patients regarding the impact of shoulder problems on their lives. One hundred eight persons participated in a randomized trial of home exercise instruction after arthroscopic repair of rotator cuff tears. Two impairment measures were used--strength estimates obtained by use of a Nicholas electronic dynamometer and range of motion in the standing position. Self- reported outcomes were measured by use of the Shoulder Pain and Disability Index (SPADI) and the University of Pennsylvania (UPenn) Shoulder Scale. Pearson correlation coefficients were calculated to estimate the associations between scores on impairment measures and self-report measures. R² values were calculated to estimate the proportion of variance shared by impairment and self-report scores. We found that the linear relationship between impairment scores and patient-reported outcomes was quite low, explaining as little as 8% of the total variance. Qualitative analysis of patient interviews suggests that patients distinguish between their impairment and their status on personally relevant outcomes. Future research should evaluate the nature of patient judgments of shoulder health outcomes.