Rater Reliability and Concurrent Validity of Single and Dual Bubble Inclinometry to Assess Cervical Lateral Flexion

The purpose of this study was to assess interrater and intrarater reliability and validity for single inclinometry (SI) and dual inclinometry (DI) assessment of cervical lateral flexion (CLF) range of motion and compare reliability in a practicing physical therapist (PT) and student PTs (SPTs).

Twenty-four subjects performed right and left CLF while SI, DI, and 3-dimensional kinematics were concurrently recorded. Subjects were reassessed by 2 SPTs and 1 PT using both SI and DI. Each subject was measured twice per rater in round-robin fashion.

There were significant positive relationships between DI and motion capture for both right (r = 0.841; P < .01) and left lateral flexion (r = 0.838; P < .01). Single inclinometry also had a significant correlation with motion capture for right (r = 0.927, P < .01) and left (r = 0.834, P < .01) lateral flexion. Interrater reliability was good for both SI and DI methods. For SI, intraclass correlation coefficient (ICC) (3,1) was 0.905 and 0.870 for right and left CLF, respectively. For DI, ICC(3,1) was 0.803 and 0.757 for right and left CLF, respectively. Intrarater reliability was good for both methods. Average SI values were ICC(2,1) of 0.928 and 0.897 for right and left CLF, respectively. Average DI values were ICC(2,1) of 0.882 and 0.851 for left and right, respectively. Although not significant, the PT had slightly higher reliability in all measures (range, 0.881-0.935) compared to the SPTs (range, 0.880-0.925).

Both SI and DI are acceptable for clinical use and both are reliable measurement methods for CLF between raters and for repeated measures. There are minimal differences in reliability between a PT with experience and SPTs with minimal experience.