Head-Cervical Spine Motion Measurement in Healthy Population: Comparison of CROM Apparatus and “G-Plus” APP on iPhone

Assessment of head-cervical spine motion (HCSM) is a vital index of functional evaluation for cervical surgery, but there is a lack of HCSM datasets in the healthy population and no suitable tools to measure HCSM in clinical practice. The objectives of this study were to obtain the normal values of HCSM in a healthy population, test the reliability and validity of an APP "G-Plus," and analyze related influencing factors of HCSM.We measured HCSM in 6 directions of 500 healthy people with a CROM apparatus and "G-Plus." The intraclass correlation coefficient (ICC) was used to test the reliability of "G-Plus." The validity of "G-Plus" measurements as compared with the CROM apparatus was tested by Bland-Altman statistics. We used multiple linear regression analysis to test the correlation among age, gender, body mass index (BMI), neck configuration (ratio of cervical circumference to cervical length), and HCSM.Excellent interrater and intrarater reliability were demonstrated for CROM (ICC:0.929-0.993) and "G-Plus" (ICC: 0.898-0.991). Bland-Altman plots demonstrated an acceptable agreement between CROM and "G-Plus." Age was negatively correlated with HCSM. HCSM in females was superior to males except for flexion. Neck configuration affected HCSM in the direction of extension, right lateral flexion, and left and right rotation. BMI was correlated with flexion and extension."G-Plus" is a reliable and convenient tool for HCSM measurement in clinical practice. The presentation of datasets of HCSM in healthy population provides a basic reference for cervical function assessment. Age, gender, BMI, and neck configuration are significantly correlated to HCSM.