Measurement of scapular asymmetry and assessment of shoulder dysfunction using the lateral scapular slide test: A reliability and validity study

Background and Purpose. The Lateral Scapular Slide Test (LSST) is used to d etermine scapular position with the arm abducted 0, 45, and 90 degrees in t he coronal plane. Assessment of scapular position is based on the derived d ifference measurement of bilateral scapular distances. The purpose of this study was to assess the reliability of measurements obtained using the LSST and whether they could be used to identify people with and without shoulde r impairments. Subjects. Forty-six subjects ranging in age from 18 to 65 ye ars (X=30.0, SD=11.1) participated in this study. One group consisted of 20 subjects being treated for shoulder impairments, and one group consisted o f 26 subjects without shoulder impairments. Methods. Two measurements in ea ch test position were obtained bilaterally. From the bilateral measurements , we derived the difference measurement. Intraclass correlation coefficient s (ICC [1,1]) and the standard error of measurement (SEM) were calculated f or intrarater and interrater reliability of the difference in side-to-side measures of scapular distance. Sensitivity and specificity of the LSST for classifying subjects with and without shoulder impairments were also determ ined. Results. The ICCs for intrarater reliability were .75, .77, and .80 a nd .52, .66, and .62, respectively, for subjects without and with shoulder impairments in 0, 45, and 90 degrees of abduction. The ICCs for interrater reliability were .67, .43, and .74 and .79, .45, and .57, respectively, for subjects without and with shoulder impairments in 0, 45 and 90 degrees of abduction. The SEMs ranged from 0.57 to 0.86 cm for intrarater reliability and from 0.79 to 1.20 cm for interrater reliability. Using the criterion of greater than 1.0 cm difference, sensitivity and specificity were 35% and 4 8%, 41% and 54%, and 43% and 56%, respectively, for 0, 45, and 90 degrees o f abduction. Sensitivity and specificity based on the criterion of greater than 1.5 cm difference were 28% and 53%, 50% and 58%, and 34% and 52%, resp ectively, for the 3 scapular positions. Conclusion and Discussion. Our resu lts suggest that measurements of scapular positioning based on the differen ce in side-to-side scapular distance measures are not reliable. Furthermore , the results suggest that sensitivity and specificity of the LSST measurem ents are poor and that the LSST should not be used to identify people with and without shoulder dysfunction.