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Shoulder outcome measures: a comparison of 6 functional tests
Jeff D Placzek1, Steven C Lukens, Sabrina Badalanmenti
1Department of Orthopaedic Surgery, Washington University School of Medicine, St Louis, Missouri, USA. placzek@oakland.edu
Background:
Several shoulder function scores are used in research, with no universally adopted standard. This study compares 6 shoulder outcome scales.
Hypothesis:
Correlations exist between shoulder outcome scales, allowing conversion between scales. Shoulder scales are correlated with age.
Study Design:
Regression and correlation study.
Methods:
Seventy subjects with shoulder pain completed 6 shoulder outcome scales. Pearson correlations were calculated between the total scores of the 6 instruments, between the components of the scales, and with age. Regression equations were calculated between scales.
Results:
The range of r values for total scores was 0.495 < or = r < or = 0.770, P < or = .01. In general, a scale's components were themselves highly correlated and added little new information to the scale (0.260 < or = r < or = 0.705, P < or = .05). Most of the scale scores were highly correlated with age (0.291 < or = r < or = 0.582, P < or = .05). Constant's reported corrections for age reduced (from r = -0.582 to r = -0.250, P < .05) but did not eliminate age as a confounding variable.
Conclusions:
Correlations exist between shoulder outcome scales, but existing shoulder scales are not equivalent in their assessments of function; they contain redundant information and, in some cases, may reflect a patient's age better than his/her shoulder function. The utility of conversion equations is minimized as a result of low to moderate correlations between scales.