The Influence of Natural Head Position on the Cervical Sagittal Alignment

INTRODUCTION: This study investigated the relationship between the parameters related to the natural head position and cervical segmental angles and alignment of patients with neck pain. MATERIAL AND METHODS: The lateral radiographs of the cervical spine were collected from 103 patients and were used to retrospectively analyze the correlation between the natural head position, cervical local sagittal angles, and alignment. Sagittal measurements were as follows: cervical curvature classification, slope of McGregor's line (McGS), local sagittal angles (C0–C2 angle, C2–C5 angle, C5–C7 angle, and C2–C7 angle), T1 slope, center of gravity of the head to sagittal vertical axis (CG–C7 SVA), and local sagittal alignment (C0–C2 SVA and C2–C7 SVA). RESULTS: McGS was significantly correlated to C0–C2 angle (r = 0.57), C0–C2 SVA (r = −0.53), C2–C7 SVA (r = −0.28), and CG–C7 SVA (r = −0.47). CG–C7 SVA was also significantly correlated to curvature type (r = 0.27), C5–C7 angle (r = −0.37), and C2–C7 angle (r = −0.39). CONCLUSIONS: A backward shift with an extended head position may accompany a relatively normal curvature of the cervical spine. The effect of posture control in relieving abnormal mechanical state of the cervical spine needs to be further confirmed by biomechanical analysis.