Reproducibility and reliability of head posture obtained by the outer canthus indicator

Young-Jae Kim; Byong-Wha Sohn; Kee-Joon Lee

doi:10.4041/kjod.2010.40.2.77

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Kim, Sohn, and Lee: Reproducibility and reliability of head posture obtained by the outer canthus indicator

Original Article

Korean Journal of Orthodontics

Korean Journal of Orthodontics 2010; 40(2): 77-86.

Published online: 30 April 2010

DOI: https://doi.org/10.4041/kjod.2010.40.2.77

Reproducibility and reliability of head posture obtained by the outer canthus indicator

Young-Jae Kim, DDS, MSD^a, Byong-Wha Sohn, DDS, MSD, PhD^b, Kee-Joon Lee, DDS, MSD, PhD^c

^aGraduate Student, Department of Orthodontics, School of Dentistry, Yonsei University, Korea.

^bFormer Professor, Department of Orthodontics, School of Dentistry, Yonsei University, Korea.

^cAssociate Professor, Department of Orthodontics, School of Dentistry, Yonsei University, Korea.

Corresponding author: Kee-Joon Lee. Department of Orthodontics, School of Dentistry, Yonsei University, 250, Seongsanno, Seodaemun-gu, Seoul 120-752, Korea. +82 2 2228 3105; orthojn@yuhs.ac

Received 25 August 2009 Revised 5 March 2010 Accepted 10 March 2010

Abstract

Objective

The purposes of this study were to evaluate the reproducibility and reliability of head posture obtained by registering outer canthus as a soft tissue landmark with the Outer Canthus Indicator (OCI).

Methods

Twenty-one adults with normal facial morphology were enrolled in this study (mean age 27.5 ± 1.72 years). To register initial head posture, height of the outer canthus from the ear rod plane was measured using OCI. Head posture was reproduced by moving the head upwards and downwards until the outer canthus was in a straight line with the indicator set at a registered height. After the head posture is reproduced by two operators after two days, lateral photographs were taken. Computerized photometric analyses of the photographs were performed.

Results

The head rotations around the transverse axis were 0.69 ± 0.43°, 0.98 ± 0.65° from each of the two operators. Standard errors were 0.09° and 0.14° each, which were similar to results from past research findings. There were no significant differences between the data from the two operators (p > 0.05). There were no correlations between the head rotation around the horizontal and vertical axes (p > 0.05).

Conclusions

The present study suggests that OCI-registered head posture may minimize errors from vertical head rotation in cephalometry and photometry.

Keywords: Head posture, Outer canthus, Outer Canthus Indicator, Photograph

Figures and Tables

Fig. 1

Major components and assembly of the Outer Canthus Indicator (OCI). Cover (1), indicator (2), ruler (3), base (4), right side arm of the cephalostat (5), and ear rod (6) (from top to bottom in the order of assembly, broken arrow) are indicated. Within the cover and the base (1, 4), the metal ruler and the indicator (2, 3) unit can move up and down (line arrow).

Fig. 2

Procedures for registering and reproducing head posture by the OCI method. To register initial head posture, move the indicator up and down (A-1) until it indicates the outer canthus (A-2). Individual height of the outer canthus from the ear rod plane (OCI value) can be registered by reading the scale on the ruler (A-3). To reproduce initial head posture, adjust the indicator to the individual OCI value (B-1). Then rotate subject's head vertically (B-2) until the outer canthus can be aligned with the indicator (B-3).

Fig. 3

Landmarks and measurements on the superimposed tracings. True vertical and true horizontal lines crossing at the ear rod point were drawn on each of the photographs taken on T0, T1. Then the tracing papers were superimposed on G, STN, NT, Sn. The angle between the true vertical lines and the distance between the ear rod points were measured on V-ceph 3.5 program (Cybermed, Korea). G, Glabella; STN, soft tissue nasion; NT, nose tip; Sn, subasale; Er, ear rod point; Tv, true vertical line; Th, true horizontal line; Dh, horizontal deviation of Er; Dv, vertical deviation of Er; Ro, angle between Tv0 and Tv1.

Fig. 4

Horizontal and vertical deviations of the ear rod point (same abbreviations as Fig 3; unit, mm).

Fig. 5

Vertical head rotation in each subject (unit, degree).

Table 1

Age distribution of the subjects in this study (Unit, year)

Table 2

Descriptive statistics of the variables

Same abbreviations as Fig 3; SD, standard deviation.

Table 3

Standard errors, maximum and minimum values of the variables

Same abbreviations as Fig 3; SE, standard error; Max, maximum; Min, minimum.

Table 4

Pearson's correlation coefficients and p values for the horizontal and vertical deviations of ear rod point

Same abbreviations as Fig 3; R, Pearson's correlation coefficient.

Notes

This study was supported by a faculty research grant of Yonsei University College of Dentistry for 2007 (6-2007-0053).

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