Download reliability of sex estimation by lateral angle method and

RELIABILITY OF SEX ESTIMATION BY
LATERAL ANGLE METHOD
AND
METRIC ANALYSIS OF REGION OF THE FORAMEN MAGNUM
Petra Panenková (1), Radoslav Beňuš (1), Soňa Masnicová (2), Dalibor Hojsík (3), Stanislav Katina (4)
(1) Department of Anthropology; Comenius University; Bratislava; Slovak Republic
(2) Department of Criminalistics and Forensic Sciences; Academy of Police Forces; Bratislava; Slovak Republic
(3) Institute of Forensic Medicine; Comenius University; Bratislava; Slovak Republic
(4) Department of Applied Mathematics and Statistics; Comenius University; Bratislava; Slovak Republic
Introduction
Estimation of sex, age, ethnicity and stature forms basic pillars of forensic anthropology. Even if it is
necessary to gain as much relevant information as it is possible; it has to be bear in mind that even if
complete skeletal remains are available, biological profile is possible to be estimated and not
determined.
In the field of forensic investigation, fragmentary skeletal human remains demand special approach to
be handled. Incompleteness of material induced subsequent osteological studies dealing with sexual
dimorphism of different parts of bones, especially those, which usually survive also bad condition of
burial or taphonomical process in relatively good state. It is necessary to test already published
methods because a set of variables, which are discriminant in one population, may not be as
discriminating when applied to a different population due to the interpopulation variation in sexual
dimorphism.
Test of accuracy of sex estimation by Lateral angle method
In terms of preservation, the petrous part of
temporal bone is one of the densest structures
in the human skeleton. Petrous portion may be
usually found also in mechanically damaged or
even cremated remains. This resistance
induced several studies to consider significance
of exhibited sexual dimorphism in petrous
portion (Wahl 1981; Norén et al. 2005; Graw et
al. 2005, Akansel et al. 2008). For testing the
sexual dimorphism the lateral angle (LA) of
meatus acousticus internus was selected, which
denotes the angle of internal acoustic canal in
relation to the medial surface of the petrous
bone (Figure 2).
Sample and methods
Figure 2.Lateral angle is denoted by two lines. The first line
g
to the anterior and posterior lips of the meatus.
is tangent
The second line is tangent to the anterior wall of the internal
acoustic canal.
mean
x
Left LA
- 0,153
43,3
y
Right LA
0,024
43,7
♂
Sectioning point
LDs
♀
0,092
b
WFM
-0,127
31,9
c
LRC
-0,128
22,5
A1-A2 – LRC - length of right occipital condyle;
C1-C2 – WRC - width of right occipital condyle;
Figure 3 and 4: Parameters measured onn foramen
magnum region (modified from Uyasal et al. 2008)
37,1
d
LLC
0,321
22,3
e
WRC
0,454
10,9
f
WLC
-0,107
11,0
g
MBD
0,045
51,6
h
MnID
0 397
0,397
98
9,8
♀
Graph 1: Boxplots of LA values in degrees for
females and males showing wide overlapping of
values
mean
LFM
Sectioning point
0
>0
A1-A2 – LFM - length of foramen magnum;
B1-B2 – WFM - width of foramen magnum;
C1-C2 – MBD - maximum bicondylar distance;
D1-D2 – MnID - minimum intercondylar distance
a
♂
<0
Probability of correct sex classification 0,568
The parameters of foramen magnum region
were measured in a total of 75 patients. Sample
comprises 38 females (age range: 15-80 years)
and 37 males (age range: 19-86 years).
The parameters of foramen magnum were
measured as follows: length (LC; LRC – right;
LLC - left) and width (WC; WRC – right; WLC left) of occipital condyle, minimum intercondylar
distance (MnID), maximum bicondylar distance
((MBD),
), length
g ((LFM)) and width ((WFM)) of
foramen magnum.
Results
Results
LDs
Test of accuracy of sex estimation by metric analysis of foramen magnum region
Another skeletal part which is usually well
preserved is foramen magnum region. The
basis of cranium is protected by large soft
ti
tissue
mass comprises
i
muscle,
l ttendon
d and
d
ligaments. As such, the occipital region
may prove useful of sex estimation in cases
of significantly fragmented remains.
Sample and methods
Data were obtained by using CT scanner
Siemens – Somatome Volume Zoom on
Radiodiagnostic ward FNsP Ružinov in
Bratislava.
The sample comprises 125 patients who
underwent CT scanning of paranasal sinuses
for diagnostic purposes.
There were sixty-four females (age range:
15-85 years) and sixty-one males (age
range: 19-61 years).
The LA was measured on axial images of
head using method modified from cadaveric
studies (Norén et al. 2005).
Figure 1. In the field of forensic anthropology findings of fragmentary and commingled skeletal
remains are not uncommon. (Photo reproduced from !!)
>0
0
<0
Probability of correct sex classification 0,8
Table 2: Linear discriminants for sex estimation
using foramen magnum region
The resultant formula for linear
discriminant function analysis follows:
sex =
[a–mean (a)]*LD(a)
+ [b–mean (b)]*LD(b)
+ [c–mean (c)]*LD(c)
+ [d–mean (d)]*LD(d)
+ [e–mean (e)]*LD(e)
+ [f–mean (f)]*LD(f)
+ [g–mean (g)]*LD(g)
+ [h–mean (h)]*LD(h)
Table 1: Linear discriminants for sex estimation by LA
The formula for linear discriminant function analysis follows: sex =
[x–mean (x)]*LD(x)
+ [y–mean (y)]*LD(y)
Discussion:
Using linear discriminant analysis the probability of correct classification of sex by using Lateral angle method is only 0.568. The blind trials of previously published studies revealed varying
percentage (66% to 83.2%) of correctly assigned sex (Norén et al. 2005; Graw et al. 2005). Akansel et al. (2008) pointed out that using extreme value characteristic for one sex will exclude the
majority of opposite. Nevertheless the practical applicability of this principle is difficult, because the selected extreme point was common neither for females nor for males.
The higher probability of correctly classified sex of fragmentary remains is when the foramen magnum is considered 0.8. In previously pubished studies percentage of correctly assigned sex
varied from 69.2 and 81% (Holland 1986; Uyasal et al. 2008;Gappert et al. 2009). Our results are in concordance with them.
The diagnostic value of LA still remains vague, overlap of LA values is very considerable.
References:
AKANSEL, G., INAN, N., KURTAS, O., TAHSIN SARISOY, H., ARSLAN, A., DEMIRCI, A., 2008: Gender and lateral angle of the internal acoustic canal meatus as measured on computer tomography of the temporal bone. Forensic Sci Int. 178:93–95
GAPPERT, R., BLACK, S., LAST, J., 2009: Sex Determination from the Occipital Condyle: Discriminant Function Analysis in an Eighteen and Nineteenth Century British Sample. Am J Phys Anthropol.138: 384 - 394
GRAW, M., WAHL, J., AHLBRECHT, M., 2005: Course of the meatus acusticus internus as criterion for sex differentiation. Forensic Sci Int. 147: 113–117
HOLLAND, T.D., 1986: Sex determination of fragmentary crania by analysis of the cranial base. Am J Phys Anthropol 70:203-208
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