Measurement proprieties of the CROM instrument for assessing head posture, neck retraction and protraction

Background The CROM instrument is widely used clinically and in research to measure neck range of motion. However, its measurement proprieties during the assessment of protraction and retraction movements were not examined so far. Objective To analyze the intra- and inter-rater reliability, the concurrent validity of the CROM for measuring head posture, retraction and protraction in healthy subjects. Methods Thirty-three asymptomatic subjects were recruited and assigned in a random order to one of two raters. After a 10-minute break, they were examined by a second rater (Assessment 1). After a 30-minutes break, both raters repeated the examination (Assessment 2). The examination consisted of measuring the head posture, maximum head protraction and maximum retraction. Each movement was repeated 3 times and measured simultaneously with the CROM and with a 3D capture system laboratory. Results The intra-rater reliability of the CROM was excellent for both raters for head posture and all head movements (ICC>0.9, 95% CI: 0.82–0.99, p < 0.01). The inter-rater reliability was excellent for head posture (ICC>0.95, 95% CI: 0.92–0.98, p < 0.01) and good-to-excellent for all movements at both time-points (ICC = 0.73–0.98, 95%CI: 0.45–0.99, p < 0.01). The validity analysis showed moderate-to-strong correlation between instruments for the head posture and head movements [(r) = -0.47 to −0.78), 95% CI: 0.99 to −0.24, p < 0.01]. Conclusion The CROM instrument has good-to-excellent reliability and adequate validity for measuring cervical position and displacement in the sagittal plane.