Korean J Orthod.  2010 Apr;40(2):77-86. 10.4041/kjod.2010.40.2.77.

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

• Kim YJ
• Sohn BW
• Lee KJ

• KMID: 2273215
• DOI: http://doi.org/10.4041/kjod.2010.40.2.77

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 +/- 0.43degrees, 0.98 +/- 0.65degrees from each of the two operators. Standard errors were 0.09degrees and 0.14degrees 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.

Keyword

Head posture; Outer canthus; Outer Canthus Indicator; Photograph

MeSH Terms

Adult
Axis, Cervical Vertebra
Cephalometry
Ear
Head
Humans
Photometry
Posture

Figure

• 

  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).

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