The Relationship Between Registered and Estimated Natural Head Position

OBJECTIVES:To study the relationship between registered and estimated natural head position.To further explore the essence of natural head position. Methods:Natural head position is a useful external-cranial reference line. It expresses the realistic head position and is more reliable than any internal-cranial reference line to some extent. There are two methods to achieve the natural head position. One is to obtain directly from marked lines or points on photographs or X-ray graphs, which is named registered head position. The other is to obtain by tuning the photographs or X-ray graphs around to place them to the natural position by the trained doctors, which is named estimated head position. Twenty-four persons were included in this study. Both the registered and the estimated natural head position were obtained. For the registered ones a mirror was used to help to adjust the person's head position, and for the estimated ones two good example pictures were used to train the evaluators. Paired sample analysis was used to compare the results. Results: No significant difference was found and there is significant correlation between them. Conclusions:Under certain circumstances, estimated natural head position can replace the registered one. Natural head position is not a 'natural' one.