Reliability Analysis of Shoulder Balance Measures

STUDY DESIGN: Observational study with 3 examiners. OBJECTIVE: To compare the reliability of shoulder balance measurement methods. SUMMARY OF BACKGROUND DATA: There are several measurement methods for shoulder balance. No reliability analysis has been performed despite the clinical importance of this measurement. METHODS: Whole spine posteroanterior radiographs (n = 270) were collected to compare the reliability of the 4 shoulder balance measures in patients with adolescent idiopathic scoliosis. Each radiograph was measured twice by each of the 3 examiners using 4 measurement methods. The data were analyzed statistically to determine the inter- and intraobserver reliability. RESULTS: Overall, the 4 radiographical methods showed an excellent intraclass correlation coefficient regardless of severity in intraobserver comparisons (>0.904). In addition, the mean absolute difference values in all methods were low and were comparatively similar (<1.73°). However, in interobserver comparisons, reliabilities were significantly decreased in the less severe radiographs, firstly on radiographical shoulder height measures (intraclass correlation coefficients >0.445, mean absolute difference <3.91°). However, the intraclass correlation coefficients in the coracoid height difference and clavicular angle methods were in the excellent range (>0.810 and >0.787, respectively) regardless of severity. In addition, the mean absolute difference values in the clavicular angle method were lower (<0.62°) than others. CONCLUSION: The higher reliability of the clavicular angle and coracoid height difference methods indicate the clinical usefulness of these methods. Physicians should selectively use the shoulder balance measurement method clinically. LEVEL OF EVIDENCE: 3.