The reliability and concurrent validity of scapular plane shoulder elevation measurements using a digital inclinometer and goniometer

This study investigated the reliability and concurrent validity of active shoulder elevation in the scapular plane (scaption) using a digital inclinometer and goniometer. Two investigators used a goniometer and digital inclinometer to measure scaption on 30 asymptomatic participants in a blinded repeated measures design. Good reliability was present with intraclass correlation coefficients (ICCs) for intrarater reliability of goniometry = 0.87, intrarater digital inclinometry = 0.88, interrater goniometry = 0.92, and interrater digital inclinometry = 0.89. The minimal detectable change (MDC95) for the interrater analysis indicated that a change equal to or greater than 8 degrees for goniometry and 9 degrees for inclinometry is required to be 95% certain that the change is not due to intertrial variability or measurement error. The concurrent validity between goniometry and digital inclinometry was excellent with an ICC value of 0.94 for both raters. The 95% limits of agreement suggest that the difference between these two measurement instruments can be expected to vary by up to ±11 degrees. The results support the interchangeable use of goniometry and digital inclinometer for measuring scaption. Clinicians and researchers should consider the MDC values presented when interpreting change during subsequent measurement sessions.