Reliability and validity of a Coda Motion 3-D Analysis system for measuring cervical range of motion in healthy subjects.

In the past two decades, many tools have been reported to measure the cervical range of motion (CROM), but most of the results are controversial in healthy individuals and/or individuals with neck pain. The Coda Motion 3-D Analysis system is a new instrument that measures three-dimensional joint movement. However, measurements of CROM using this system have yet to be conducted. Here, we investigate the reliability and validity of the Coda Motion 3-D Analysis System for measuring CROM in healthy adults. Sixty healthy volunteers were involved in this reliability study. Two trained investigators (M1 and M2) used the Coda Motion 3-D Analysis System to measure CROM. M1 and M2 measured all the volunteers once independently; after a short rest, M1 then measured all of them again. The intraclass correlation coefficient (ICC), standard error of the measurements (SEM), smallest detectable difference (SDD), a scatter diagram, and the limits of agreement (LoAs) were applied to evaluate the inter-tester and intra-tester reliability. Thirty healthy volunteers were involved in this validity study. The cervical flexion and extension ranges of motion were measured simultaneously with both the Coda Motion 3-D Analysis System and X-ray. A scatter diagram, the Pearson correlation coefficient and LoAs were used to evaluate the validity. Excellent intra-tester and inter-tester reliabilities were observed for the Coda Motion 3-D Analysis System (intra-tester ICC: 0.84-0.95, inter-tester ICC: 0.84-0.90). Good validity was achieved in extension and flexion with Pearson correlation coefficients ranging from 0.78 to 0.91. The Coda Motion 3-D Analysis System has excellent reliability for the measurement of CROM and good validity for measurements of flexion and extension in healthy subjects. This system has the potential to be used to measure the normal active CROM in the clinic and is accurate, safe, non-invasive, and radiation free.