Inclinometer method for recording and transferring natural head position in cephalometrics

The purposes of this study were (1) to construct a device to record natural head position and transfer it to the cephalostat, (2) to assess its clinical use, and (3) to evaluate the reproducibility of lateral cephalograms taken with the device. The device, incorporated into a pair of eyeglass frames, included 2 tilt sensors to measure pitch and roll of the head. The natural head positions of 20 subjects were established 10 times by self balance and mirror position, recorded with the device, and reproduced in the cephalostat by using the average of these 10 measurements. Three lateral cephalograms were obtained in this manner at 30-minute intervals. The first 2 films were made with the subject wearing the device to assess the reproducibility of the recorded position in the cephalostat by the inclinometer. During exposure of the third film, the device was not worn, and this film was used to determine the stability of the established position when the inclinometer was removed. The results revealed method errors of 0.6 degrees (SD, 0.9) between the first 2 sets of radiographs with a correlation coefficient of 0.985. Method errors between the first and third and the second and third sets were 0.6 degrees (SD, 0.8) and 0.7 degrees (SD, 1), respectively, with correlation coefficients of 0.989 and 0.982. The reproducibility of the method was high, and the system was clinically practical for both recording and transferring natural head position in cephalometrics. This technique should make it possible to measure and reproduce head position accurately. Minimizing the size of the device, making it radiolucent, and integrating it into the radiographic device will make it more versatile and decrease error.