Reliability and Validity of a Clinical Assessment Tool for Measuring Scapular Motion in All 3 Anatomical Planes

CONTEXT: A single clinical assessment device that objectively measures scapular motion in each anatomical plane is not currently available. The development of a novel electric goniometer affords the ability to quantify scapular motion in all three anatomical planes. OBJECTIVE: Investigate the reliability and validity of an electric goniometer to measure scapular motion in each anatomical plane during arm elevation. DESIGN: Cross-sectional. SETTING: Laboratory setting. PATIENTS OR OTHER PARTICIPANTS: Sixty participants (29 females, 31 males) were recruited from the general population. INTERVENTION(S): An electric goniometer was used to record clinical measurements of scapular position at rest and total arc of motion (excursion) during active arm elevation in two testing sessions separated by several days. Measurements were recorded independently by two examiners. In one session, scapular motion was recorded simultaneously with a 14-camera three-dimensional optical motion capture system. MAIN OUTCOME MEASURES: Reliability analysis included examination of clinical measurements for scapular position at rest and excursion during each condition. Both the intra-rater reliability between testing sessions and the inter-rater reliability recorded within the same session were assessed using Intraclass Correlation Coefficients (ICC2,3). The criterion-validity was examined by comparing the mean excursion values of each condition recorded by the electric goniometer to the 3D optical motion capture system. Validity was assessed by evaluating the average difference and root mean square error (RMSE). RESULTS: The between session intra-rater reliability was moderate to good (ICC2,3: 0.628-0.874). The within session inter-rater reliability was moderate to excellent (ICC2,3: 0.545-0.912). The average difference between the electric goniometer and 3D optical motion capture system ranged from -7° to 4° and the RMSE was between 7-10°. CONCLUSIONS: The reliability of scapular measurements is best when a standard operating procedure is used. The electric goniometer provides an accurate measurement of scapular excursions in all three anatomical planes during arm elevation