Reproducibility of asymmetry measurements of the mandible in three-dimensional CT imaging

Go-Woon Kim; Jae-Hyung Kim; Ki-Heon Lee; Hyeon-Shik Hwang

doi:10.4041/kjod.2008.38.5.314

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Reproducibility of asymmetry measurements of the mandible in three-dimensional CT imaging

Original Article

Korean J Orthod 2008;38(5):314-327.

Published online: 19 January 2008

DOI: https://doi.org/10.4041/kjod.2008.38.5.314

Reproducibility of asymmetry measurements of the mandible in three-dimensional CT imaging

Go-Woon Kim, DDS, MSD^a, Jae-Hyung Kim, DDS, MSD, PhD^b, Ki-Heon Lee, DDS, MSD, PhD^c, Hyeon-Shik Hwang, DDS, MSD, PhD^d

^aGraduate Student, Department of Orthodontics, School of Dentistry, Chonnam National University

^bAssistant Professor, Department of Oral Medicine, School of Dentistry, Chonnam National University

^cAssociate Professor, Department of Orthodontics, School of Dentistry, Chonnam National University

^dProfessor, Department of Orthodontics, 2nd Stage of Brain Korea 21, School of Dentistry, Dental Science Research Institute, Chonnam National University

Corresponding author: Hyeon-Shik Hwang. Department of Orthodontics, Chonnam National University Hospital, Hak-Dong 8, Dong-Gu, Gwangju 501-757, Korea. +82 62 220 5486; e-mail, hhwang@chonnam.ac.kr.

Received 7 June 2007 Revised 23 January 2008 Accepted 26 January 2008

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective:

The purpose of this study was to evaluate the reproducibility of measurements representing asymmetry of the mandible and to identify which landmarks would be more useful in 3-dimensional (3D) CT imaging.

Methods:

Facial CT images were obtained from forty normal occlusion individuals. Eighteen landmarks were established from the condyle, gonion, and menton areas, and 25 measurements were constructed to represent asymmetry of the mandible; 8 for ramus length, 12 for mandibular body length, 1 for condylar neck length, 2 for frontal ramal inclination, and 2 for lateral ramal inclination. Inter- and intra-examiner reproducibility of the measurements was evaluated.

Results:

Inter-examiner reproducibility of the measurements proved to be high except for 3 measurements. Intra-examiner reproducibility also proved to be high except for 2 measurements. Inter-and intra-examiner reproducibility of the measurements including Gonion proved to be low.

Conclusions:

The results of the present study indicate that the landmarks and measurements constructed in 3D CT images can be used for the diagnosis of facial asymmetry.

Keywords: Facial asymmetry, 3D CT, Landmarks, Reproducibility

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Fig 1.

Three-dimensional image was constructed using V-works^TM program.

Fig 2.

A, Construction of three-dimensional reference planes for measuring frontal and lateral ramal inclination (MSR plane; midsagittal plane, FH plane; Frankfort horizontal plane). B, The SOD file of the mandible was made in order to observe the mandible only.

Fig 3.

Three-dimensional landmarks constructed. A, Anterior view; B, lateral view; C, postero-lateral view; D, posterior view; E, superior view; F, inferior view. The landmarks are described in Table 1.

Table 1.

Description of three-dimensional landmarks constructed in this study

Landmarks	Abbreviation	Description
Condyle area
Condylion superius
	Cd_{sup_sup}	The most superior point of the condyle head on superior view
Condylion posterius
	Cd_{post_lat}	The most posterior point of the condyle head on lateral view
	Cd_{post_post}	The most posterior point of the condyle head on posterior view
Condylion lateralis
	Cd_{lat_ant}	The most lateral point of the condyle head on anterior view
	Cd_{lat_lat}	The most lateral point of the condyle head on lateral view
Sigmoid notch
	S	The most inferior point of sigmoid notch
Gonion area
Gonion inferius
	Go_{inf_lat}	The most inferior point of curvature along angle of mandible on lateral view
	Go_{inf_inf}	The most inferior point of curvature along angle of mandible on inferior view
Gonion midpoint
	Go_{mid_lat}	The midpoint of curvature along angle of mandible on lateral view
	Go_{mid_obl}	The midpoint of curvature along angle of mandible on postero-lateral view
Gonion posterius
	Go_{post_lat}	The most posterior point of curvature along angle of mandible on lateral view
	Go_{post_post}	The most posterior point of curvature along angle of mandible on posterior view
Gonion lateralis
	Go_{lat_ant}	The most lateral point of the gonion area on anterior view
	Go_{lat_lat}	The most lateral point of the gonion area on lateral view
Antegonion
	Ag_{_lat}	The most superior point of antegonial notch of mandible on lateral view
	Ag_{_inf}	The most superior point of antegonial notch of mandible on inferior view
Menton area
Menton
	Me_{_ant}	The most inferior point on symphyseal outline on anterior view
	Me_{_inf}	The most inferior point on symphyseal outline on inferior view

Table 2.

Linear and angular measurements constructed

Variables	Measurements
Ramus length (mm)
	Cd_{sup_sup} - Go_{inf_lat}
	Cd_{sup_sup} - Go_{inf_inf}
	Cd_{sup_sup} - Go_{mid_lat}
	Cd_{sup_sup} - Go_{mid_obl}
	Cd_{sup_sup} - Go_{post_lat}
	Cd_{sup_sup} - Go_{post_post}
	Cd_{sup_sup} - Ag_{_lat}
	Cd_{sup_sup} - Ag_{_inf}
Mandibular body length (mm)
	Go_{inf_lat} - Me_{_ant}
	Go_{inf_lat} - Me_{_inf}
	Go_{inf_inf} - Me_{_ant}
	Go_{inf_inf} - Me_{_inf}
	Go_{mid_lat} - Me_{_ant}
	Go_{mid_lat} - Me_{_inf}
	Go_{mid_obl} - Me_{_ant}
	Go_{mid_obl} - Me_{_inf}
	Go_{post_lat} - Me_{_ant}
	Go_{post_lat} - Me_{_inf}
	Go_{post_post} - Me_{_ant}
	Go_{post_post} - Me_{_inf}
Condylar neck length (mm)
	Cd_{sup_sup} - S
Frontal ramal inclination (deg)
	Cd_{lat_ant} - Go_{lat_ant} to MSR plane
	Cd_{lat_lat} - Go_{lat_lat} to MSR plane
Lateral ramal inclination (deg)
	Cd_{post_lat} - Go_{post_lat} to FH plane
	Cd_{post_post} - Go_{post_post} to FH plane

Table 3.

Results of ANOVA test and intraclass correlation coefficient showing inter-examiner reproducibility of measurements (n = 40)

Measurements	A	B	C	D	ANOVA (p value)	ICC
Measurements	Mean±SD	Mean±SD	Mean±SD	Mean±SD	ANOVA (p value)	ICC
Ramus length (mm)
Cd_{sup_sup} -Go_{inf_lat}	71.18±6.49	71.68±6.69	71.69±6.59	71.69±6.36	NS	0.967
Cd_{sup_sup} -Go_{inf_inf}	71.93±6.36	71.65±6.69	71.79±6.62	72.39±6.28	NS	0.969
Cd_{sup_sup} -Go_{mid_lat}	63.79±5.69	63.24±6.23	64.77±6.46	65.56±6.12	NS	0.909
Cd_{sup_sup} -Go_{mid_obl}	62.71±5.47	63.30±6.26	64.70±6.45	66.54±5.77	0.015	0.824
Cd_{sup_sup} -Go_{post_lat}	54.00±4.94	52.79±5.77	54.62±5.68	52.28±4.18	NS	0.867
Cd_{sup_sup} -Go_{post_post}	53.30±4.81	52.67±5.56	54.64±5.91	52.21±4.41	NS	0.862
Cd_{sup_sup} -Ag_{_lat}	75.42±6.00	75.23±6.29	74.83±5.91	75.37±5.80	NS	0.908
Cd_{sup_sup} -Ag_{_inf}	76.13±6.06	75.30±6.33	75.05±5.90	76.32±5.76	NS	0.907
Mandibular body length (mm)
Go_{inf_lat} -Me_{_ant}	81.69±4.86	81.14±5.30	81.29±4.41	80.90±4.88	NS	0.887
Go_{inf_lat} -Me_{_inf}	80.19±5.23	81.12±5.35	81.29±4.68	80.76±5.30	NS	0.873
Go_{inf_inf}-Me_{_ant}	81.21±5.01	81.17±5.57	81.22±4.59	80.91±5.11	NS	0.881
Go_{inf_inf} -Me_{_inf}	79.86±5.52	81.08±5.56	80.77±4.78	80.03±5.59	NS	0.871
Go_{mid_lat} -Me_{_ant}	90.33±5.87	91.69±5.64	89.27±5.51	89.15±5.79	NS	0.884
Go_{mid_lat}-Me_{_inf}	89.01±6.36	91.30±5.93	88.83±5.86	89.32±6.00	NS	0.888
Go_{mid_obl} -Me_{_ant}	90.06±6.18	91.66±5.76	88.99±5.87	88.31±6.10	0.040	0.860
Go_{mid_obl} -Me_{_inf}	88.80±6.57	91.26±5.76	88.38±6.06	88.50±6.35	0.048	0.868
Go_{post_lat} -Me_{_ant}	96.21±5.85	97.46±5.79	95.62±5.90	95.86±6.81	NS	0.928
Go_{post_lat} -Me_{_inf}	94.95±6.28	97.35±5.91	95.41±6.01	96.31±6.73	NS	0.921
Go_{post_post} -Me_{_ant}	95.66±6.09	97.40±5.92	95.44±5.89	96.12±6.63	NS	0.925
Go_{post_post} -Me_{_inf}	94.51±6.46	97.06±5.96	94.93±6.06	96.29±6.70	NS	0.906
Condylar neck length (mm)
Cd_{sup_sup} -S	27.64±3.27	28.08±3.50	28.38±5.74	28.52±3.40	NS	0.865
Frontal ramal inclination (^o)
Cd_{lat_ant} -Go_{lat_ant} to MSR plane	12.92±2.79	12.87±2.82	12.70±2.80	12.92±2.67	NS	0.859
Cd_{lat_lat} -Go_{lat_lat} to MSR plane	13.07±2.81	12.95±2.88	13.09±2.82	12.94±2.74	NS	0.844
Lateral ramal inclination (^o)
Cd_{post_lat} -Go_{post_lat} to FH plane	80.82±3.17	80.83±2.73	80.79±3.05	81.03±2.76	NS	0.831
Cd_{post_post} -Go_{post_post} to FH plane	80.12±3.07	80.42±2.92	80.37±3.12	80.54±2.81	NS	0.881

NS, not significant; ICC, intraclass correlation coefficient; excellent > 0.800.

Table 4.

Post-hoc comparison by Tukey grouping in the measurements showing significant difference between exam-iners

Measurements		Mean±SD			p value
Ramus length
Cd_{sup_sup} -Go_{mid_obl}	A	B	C	D
	62.71±5.71	63.3±6.26	64.7±6.45	66.54±5.77	0.015
Mandibular body length
Go_{mid_obl} -Me_{_ant}	D	C	A	B
	88.31±6.10	88.99±5.87	90.06±6.18	91.66±5.76	0.040
Gomid_obl -Me_inf	C	D	A	B
	88.38±6.06	88.5±6.35	88.8±6.57	91.26±5.76	0.048

Groups connected by horizontal bars were not significantly different.

Table 5.

Results of t-test showing intra-examiner reproducibility of measurements (n = 40)

Measurements	1st measure	2nd measure	Significance
Measurements	Mean±SD	Mean±SD	Significance
Ramus length (mm)
Cd_{sup_sup} -Go_{inf_lat}	71.18±6.49	71.20±6.49	NS
Cd_{sup_sup} -Go_{inf_inf}	71.99±6.36	71.68±6.43	NS
Cd_{sup_sup} -Go_{mid_lat}	63.79±5.69	64.22±5.57	NS
Cd_{sup_sup} -Go_{mid_obl}	62.71±5.47	63.53±5.80	0.036
Cd_{sup_sup} -Go_{post_lat}	54.00±4.94	54.27±4.33	NS
Cd_{sup_sup} -Go_{post_post}	53.30±4.81	53.66±4.52	NS
Cd_{sup_sup} -Ag_{_lat}	75.42±6.00	75.31±6.26	NS
Cd_{sup_sup} -Ag_{_inf}	76.13±6.06	76.00±6.18	NS
Mandibular body length (mm)
Go_{inf_lat} -Me_{_ant}	81.69±4.86	81.71±4.65	NS
Go_{inf_lat} -Me_{_inf}	80.19±5.23	80.45±4.82	NS
Go_{inf_inf} -Me_{_ant}	81.21±5.01	81.17±4.69	NS
Go_{inf_inf} -Me_{_inf}	79.86±5.52	79.76±5.01	NS
Go_{mid_lat} -Me_{_ant}	90.33±5.87	90.57±6.06	NS
Go_{mid_lat} -Me_{_inf}	89.01±6.36	89.27±6.24	0.035
Go_{mid_obl} -Me_{_ant}	90.06±6.11	90.58±6.15	NS
Go_{mid_obl} -Me_{_inf}	88.80±6.57	89.08±6.71	NS
Go_{post_lat} -Me_{_ant}	96.21±5.85	95.78±6.21	NS
Go_{post_lat} -Me_{_inf}	94.95±6.28	94.85±6.28	NS
Go_{post_post} -Me_{_ant}	95.66±6.09	95.63±6.17	NS
Go_{post_post} -Me_{_inf}	94.51±6.46	94.52±6.41	NS
Condylar neck length (mm)
Cd_{sup_sup} -S	27.64±3.27	27.69±3.00	NS
Frontal ramal inclination (°)
Cd_{lat_ant}-Go_{lat_ant} to MSR plane	12.92±2.79	12.90±2.80	NS
Cd_{lat_lat} -Go_{lat_lat} to MSR plane	13.07±2.81	13.09±2.82	NS
Lateral ramal inclination (°)
Cd_{post_lat} -Go_{post_lat} toFH plane	80.82±3.17	80.79±3.05	NS
Cd_{post_post} -Go_{post_post} to FH plane	80.12±3.07	80.39±3.12	NS

NS, not significant.

Table 6.

Pearson correlation coefficient and reliability coefficient between first and second measurements showing intra-examiner reproducibility

Measurements	Pearson correlation coefficient	Reliability coefficient
Ramus length
Cd_{sup_sup} -Go_{inf_lat}	0.992	0.992
Cd_{sup_sup} -Go_{inf_inf}	0.992	0.991
Cd_{sup_sup} -Go_{mid_lat}	0.965	0.963
Cd_{sup_sup} -Go_{mid_obl}	0.911	0.901
Cd_{sup_sup} -Go_{post_lat}	0.936	0.928
Cd_{sup_sup} -Go_{post_post}	0.921	0.918
Cd_{sup_sup} -Ag_{_lat}	0.973	0.973
Cd_{sup_sup} -Ag_{_inf}	0.981	0.981
Mandibular body length
Go_{inf_lat} -Me_{_ant}	0.947	0.947
Go_{inf_lat} -Me_{_inf}	0.954	0.951
Go_{inf_inf} -Me_{_ant}	0.934	0.934
Go_{inf_inf} -Me_{_inf}	0.959	0.955
Go_{mid_lat} -Me_{_ant}	0.970	0.969
Go_{mid_lat} -Me_{_inf}	0.983	0.982
Go_{mid_obl} -Me_{_ant}	0.971	0.968
Go_{mid_obl} -Me_{_inf}	0.973	0.973
Go_{post_lat} -Me_{_ant}	0.954	0.951
Go_{post_lat} -Me_{_inf}	0.988	0.988
Go_{post_post} -Me_{_ant}	0.983	0.983
Go_{post_post} -Me_{_inf}	0.971	0.972
Condylar neck length
Cd_{sup_sup} -S	0.914	0.913
Frontal ramal inclination
Cd_{lat_ant}-Go_{lat_ant} to MSR plane	0.990	0.943
Cd_{lat_lat} -Go_{lat_lat} to MSR plane	0.988	0.970
Lateral ramal inclination
Cd_{post_lat} -Go_{post_lat} to FH plane	0.949	0.975
Cd_{post_post} -Go_{post_post} to FH plane	0.941	0.948

All values were statistically significant (p < 0.001).

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