The purpose of this study was to investigate the relationship between the head and neck posture and the cervical curvature, especially in forward head posture(FHP). Sixty patients with craniomandibular disorders and thirty dental students without any signs and symptoms of craniomandibular disorders participated in this study as patient group and as control group, respectively. The author evaluated the head and neck posture of all subjects by plumb line and CROM(cervical-range-of-motion), and had taken cephalograph in natural head position. On the cephalogragh the angle of cervical inclination formed by true horizontal plane and 4th cervical vertebra(C4) and the radius of cervical curvature from C1 to C5 were measured. A specially designed ruler was used for measuring cervical curvature. Occlusal contact number and force with T-scan system, electromyographic activity of cervical muscles with Bio-EMG, and distance of freeway- space with Bio-EGN were recorded, respectively. The collected data were -, processed by SAS/STAT program.
The obtained results were as follows
1. In subjects with longer radius which was less cervical curvature, head positioned more anteriorly than subjects with smaller radius, and they showed slightly straight cervical vertebra.
2. Between the patients and the control group, there were no differences in cervical curvature, in forward head position by plumb line and in CROM. But the patient group had a greater cervical inclination(CVT/HOR) than the control group had.
3. There were positive correlations between cervical curvature and forward head position by plumb line, between forward head position by plumb line and that by CROM in patient group. The cervical inclination (CVT/HOR), however, had negative correlations with cervical curvature, and with forward head position by plumb line, respectively.
4. In case of showing more cervical curvature and more forward head position by plumb line, the head position was defined as forward head posture(FHP).
In patient group, subjects without forward head posture showed greater posterior teeth contact force than subjects with forward head posture, but in control group, there were no difference between the two subjects.
5. There were higher electromyographic activity in almost all muscles and smaller freeway space in induced forward head posture than those in natural head position in subjects without forward head posture.
In conclusion, head position of patients with craniomandibular disorders were not more anterior than that of norm´, control persons, but they had tendency to head extension. From the result of this study, forward head posture could be defined as posterior rotation of upper cervical segment with a straight lower cervical segment due to loss of normal lordosis.
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