J Manipulative Physiol Ther. 1996 Jun; 19(5): 296-301.

A radiographic comparison of neutral cervical posture with cervical flexion and extension ranges of motion.

Miller JS, Polissar NL, Haas M.

Mountain-Whisper-Light Statistical Consulting, Seattle, WA, USA.

OBJECTIVE: To radiographically assess, using a pilot study, the relationship between the neutral cervical curve and cervical segmental ranges of motion (ROM) for flexion and extension in asymptomatic subjects. DESIGN: Survey. SETTING: Chiropractic college student health center and private practice. PATIENTS: Sixteen asymptomatic adult students with no radiographic evidence of degenerative changes. INTERVENTION: No therapeutic intervention. MAIN OUTCOME MEASURES: Neutral segmental alignment and flexion and extension segmental ranges of motion for C2-C6 evaluated relative to the subjacent segment. RESULTS: Correlations between neutral posture variables (segmental tilt and global posture) and their corresponding ROMs (segmental and global) were computed. A strong correlation was found for flexion at C4 (r = -.76, p = .0006) and at C5 (r = -.84, p = .0001). Correlations were not as strong at other vertebral levels for flexion and at all levels for extension (r = .01 to r = .52). The error in prediction of motion from neutral posture is given by the standard error of the estimate (SEE). The SEE for flexion ROM ranged from 2.6 degrees at C5 to 3.9 degrees at C6, and the SEE for extension ranged from 3.8 degrees at C4 to 6.5 degrees at C2. CONCLUSION: Correlation between neutral cervical posture and flexion or extension ranges of motion was only strong at the C4 and C5 vertebral levels. Generally, there was not good predictability of ROM from neutral posture as indicated by the R2 values and the standard errors of estimate. Further investigation is needed to determine if other variables, such as angle of the facet joints, may be influential in these postural-functional relationships.