The authors conducted this study in order to investigate the reliability, minimal detectable change (MDC90) and concurrent validity of a gravity-based bubble inclinometer (inclinometer) and iPhone® application for measuring standing lumbar lordosis. For the study, two investigators used both an inclinometer and an iPhone® with an inclinometer application to measure lumbar lordosis of 30 participants with no symptoms. ICC models 3,k and 2,k were used for the intrarater and interrater analysis, respectively. They found good interrater and intrarater reliability in the inclinometer with Intraclass Correlation Coefficients (ICC) of 0.90 and 0.85, respectively and the iPhone® application with ICC values of 0.96 and 0.81. They suggested that the minimal detectable change (MDC90) indicated that a change greater than or equal to 7° and 6° is needed to exceed the threshold of error using the iPhone® and inclinometer, respectively. The concurrent validity between the two instruments was found to be good with a Pearson product-moment coefficient of correlation (r) of 0.86 for both raters. 95% limits of agreement identified differences ranging from 9° greater in reference to the iPhone® to 8° less for the inclinometer.
They found that both the inclinometer and iPhone® application possess good interrater reliability, intrarater reliability and concurrent validity for measuring standing lumbar lordosis. Their investigation offers preliminary evidence to suggest that smart phone applications may offer clinical utility similar to inclinometry for quantifying standing lumbar lordosis. They add that clinicians should identify possible individual differences when working with these tools interchangeably.