Cooke M S
Department of Children's Dentistry and Orthodontics, Faculty of Dentistry, Prince Philip Dental Hospital, University of Hong Kong.
Am J Orthod Dentofacial Orthop. 1990 Jun;97(6):489-94. doi: 10.1016/S0889-5406(05)80029-0.
Natural head posture (NHP) is being increasingly used as the logical reference position for the evaluation of craniofacial morphology. The basic premise underlying its use is that the long-term clinical reproducibility (variability) of NHP is significantly less than the variability of conventional intracranial reference planes with respect to the vertical. This study reports the results of a 5-year longitudinal study evaluating the reproducibility over time of NHP lateral cephalometric radiographs. The subjects were 126 randomly selected Chinese children in Hong Kong who were first assessed at the age of 12 years. Thirty subjects were recorded after 5 years. NHP reproducibility deteriorated over time but showed signs of stabilizing after 1 to 1 1/2 years. The method error was 1.93 degrees after 1 to 2 hours, 2.34 degrees after 3 to 6 months, and 3.04 degrees after 5 years. The individual variability of NHP reproducibility also increased over time. The standard deviation of the SN/vertical angulation was 2.61 degrees after 1 to 2 hours, 3.16 degrees after 3 to 6 months, and 4.20 degrees after 5 years. Further longitudinal data are required to determine whether NHP reproducibility continues to deteriorate after 5 years. After 5 years, however, the variance of NHP (9.24 degrees [= 3.04(2)]) remains significantly less than the variance of intracranial reference planes to the vertical (25 degrees to 36 degrees).
自然头位（NHP）越来越多地被用作评估颅面形态的合理参考位置。其使用的基本前提是，NHP在长期临床中的可重复性（变异性）在垂直方向上明显小于传统颅内参考平面的变异性。本研究报告了一项为期5年的纵向研究结果，该研究评估了NHP侧位头影测量X线片随时间的可重复性。研究对象为126名从香港随机选取的中国儿童，他们在12岁时首次接受评估。5年后记录了30名受试者的情况。NHP的可重复性随时间推移而变差，但在1至1年半后显示出稳定的迹象。1至2小时后的方法误差为1.93度，3至6个月后为2.34度，5年后为3.04度。NHP可重复性的个体变异性也随时间增加。SN/垂直角度的标准差在1至2小时后为2.61度，3至6个月后为3.16度，5年后为4.20度。需要进一步的纵向数据来确定5年后NHP的可重复性是否会继续变差。然而，5年后，NHP的方差（9.24度[=3.04(2)]）仍明显小于颅内参考平面相对于垂直方向的方差（25度至36度）。
