Reliability and validity of a clinical assessment tool for measuring scapular motion in all 3 anatomical planes

Abstract

Context: A single clinical assessment device that can be used to objectively measure scapular motion in each anatomical plane is not currently available. The development of a novel electric goniometer would allow scapular motion in all 3 anatomical planes to be quantified. Objective: To investigate the reliability and validity of an electric goniometer for measuring scapular motion in each anatomical plane during upper extremity elevation. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: Sixty participants (29 women, 31 men; age = 30 6 14 years, height = 1.73 6 0.10 m, mass = 75.32 6 16.90 kg) 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 upper extremity elevation in 2 testing sessions separated by several days. Measurements were recorded independently by 2 examiners. In 1 session, scapular motion was recorded simultaneously using a 14- camera, 3-dimensional optical motion-capture system. Main Outcome Measure(s): Reliability analysis included examination of clinical measurements for scapular position at rest and excursion during each condition. Both the intrarater reliability between testing sessions and the interrater reliability recorded in the same session were assessed using intraclass correlation coefficients (ICCs [2,3]). The criterion validity was examined by comparing the mean excursion values of each condition recorded using the electric goniometer and the 3-dimensional optical motion-capture system. Validity was assessed by evaluating the average difference and root mean square error. Results: The between-sessions intrarater reliability was moderate to good (ICC [2,3] range = 0.628-0.874). The withinsession interrater reliability was moderate to excellent (ICC [2,3] range = 0.545-0.912). The average difference between total excursion values recorded using the electric goniometer and the 3-dimensional optical motion-capture system ranged from 7° to 4°, and the root mean square error ranged from 7° to 10°. Conclusions: The reliability of scapular measurements was best when a standard operating procedure was used. The electric goniometer provided an accurate measurement of scapular excursions in all 3 anatomical planes during upper extremity elevation.