Anthropometry study using adult Pelvic 3D Ct For Determining Sexes at Dr. Soetomo General Hospital, Indonesia

Pelvic bones are the most reliable indicator of sex in adults because of its sexual dimorphism. Medical imaging modalities e.g. Computed Tomography (CT) provide data sources to examine modern human variation quantitatively. This study aims to determine pelvic anthropometry characteristics and logistic regression formula for adult sex identication obtained from pelvic 3D CT. Methods This study was an observational analytical study with retrospective regression and cross-sectional approach. The population was all patients in Radiology Installation of Dr. Soetomo General Hospital, Surabaya, Indonesia, from September to December 2019 who underwent pelvic 3D CT examination. Then, age distribution and pelvic measurements data were obtained. In this case, statistical analysis was conducted for all the data obtained.


Introduction
Sex identi cation on remaining human bone is the rst step to do in helping forensic anthropologists to identify a person. 1 The accuracy of sex identi cation depends on bone components that are analyzed and the technique used. Forensic anthropology is a branch of applied physical anthropology that combines a variety of modi ed scienti c techniques and skills from many scienti c disciplines and is used to answer medico-legal related questions. Some of these techniques are quantitative and can be tested empirically e.g. sex and age estimation technique from unidenti ed bone remains. 2,3 Conventionally, anthropologists have relied on metric and non-metric observational analyses of actual bones. 3 Medical imaging modalities e.g. Computed Tomography (CT) provide data sources to examine modern human variation quantitatively when expanding the resources for osteological assessment to researchers. These studies have shown signi cant improvements in accuracy and reproducibility over conventional linear methods of constructing a person's biological pro le. 4,5 Various attempts have been made to be able to 'metricize' or measure non-metric properties accurately in several body areas. 5,6 More objective data for sex estimation might allow very accurate results along with metricization of certain non-metric pelvis areas. 1 Moreover, other pelvic indices such as those used in clinical medicine might be used to supplement and give additional measurements in anthropological assessment. In adults, pelvic bones are the most reliable indicator of sex because of its sexual dimorphism. Each population must have a special identi cation standard. 3 This study aims to determine pelvic anthropometry characteristics obtained from pelvic 3D CT in identifying adults' sex in Dr. Soetomo General Hospital, Surabaya, Indonesia.

Study design
This study was an observational analytical study with retrospective regression and cross-sectional approach. The population was all patients in Radiology Installation of Dr. Soetomo General Hospital, Indonesia, from September to December 2019 who underwent pelvic 3D CT examination. All methods were carried out in accordance with relevant guidelines and regulations

Sample of study
The sample of this study was pelvic 3D CT data which obtained from consecutive sampling that suited to the inclusion and exclusion criteria. The inclusion criteria were pelvic 3D CT images of Radiology Installation's patients, both male and female patients whose age more than 18 years old and CT scan image of non-pregnant women. On the other hand, the exclusion criteria in this study were pelvic 3D CT images of patient's pelvis and sacrum which reveal a pathological condition that might interfere measurement, chronic disease and osteoporosis.

Ethical clearance
The study was performed according to the Ethical principles of declarations of Helsinki. This study was approved by Medical Research Ethic Committee of Dr. Soetomo General Hospital, Surabaya for ethical clearance with registration number: 0106/LOF/301.4.2/VIII/2020. All participants included had given their written informed consent to participate in this study.

Study procedure
Pelvic CT scans examinations in the form of digital data served as study material. Furthermore, radiological examination tool used a 16-slices Siemens SOMATOM CT scan machine in Radiology Installation of Dr. Soetomo Surabaya General Hospital. Demographic data were obtained from medical records.
The age distribution and pelvic measurements data were obtained as well. Pelvic measurements that were obtained in this study are portrayed in Table 1. Distance between acetabular junction and the innermost point of ischial tuberosity (taken from the right side)

12.
Right pubic length (RPL) Distance between a point at acetabular junction and the superior point at pubic symphysis (taken from the right side)

13.
Right width of greater sciatic notch (RGSN) The line between iliac spine, the innermost part of greater sciatic notch, and ischial spine (taken from the right side)

14.
Right iliac breadth (RIB) Distance between anterior superior iliac spine to left superior posterior iliac spine (taken from the right side) 15

Study sample demography
There were 204 patients who were included in this study. Most of the samples were male with female-tomale ratio of 1:1.13.
Mean age of the patients was 50.23 ± 14.36 years and the mean age of male group older than female group. Patient's age was divided according to age group, with an age range of 10 years for each group. Group with the most patients was 41-50 years age group and followed by 51-60 years age group. Most men were included in 51-60 years age group while most female were included in 41-50 years age group (Table 2).

Radiologic components
In this study, radiologic components consist of pelvic measurement results. Pelvic measurement values were taken for the entire sample. Data were presented in the form of mean and standard deviation and further divided by sex. Table 3 provides pelvic measurement results.
Several variables were found to have a greater size for men than women i.e. ABS, AHS, bilateral IB, bilateral IH, RIL, PSL.  Table 4.

Making statistical models with logistic regression statistical analysis
Multivariate calculations were performed using binomial logistic regression on four variables with the highest correlation strength. Logistic regression calculations are presented in Table 4. From Table 4, it can be seen that the variable with a signi cant value for further use in logistic regression formula model from calibration group were CPID (p = 0.035), LIH (p = 0.001) and SPA (p = 0.015).

Table 5 Omnibus test of logistic regression model coe cients in calibration group
Step 1 Chi-square df p Step 1 Step 133. If the result > 0 the predicted sex is female, whereas, if the result < 0 the predicted sex is male.

Logistic regression model validity
Logistic regression model was applied in the studied groups to determine the formula accuracy. Data of model validity are presented in Table 6.

Discussion
Sex identi cation of skeletal remains is an important issue in forensic medicine. 2 The pelvic bones are the most reliable gender differentiation parameter because it is the most dimorphic bone, especially in adult individuals. 2 Each population has its special identi cation standard. 2 Implementing visual or morphological techniques is the quick way to assess the samples. The weakness of this technique is in the sense of a very subjective assessment which requires an experienced observers and the level of accuracy is still not guaranteed. Moreover, sexual dimorphism varies geographically. Therefore, forensic anthropologists are constantly trying to test the existing methods and developing standards that are more e cient and objective in which it can optimize the positive identi cation of the human skeleton. [7][8][9][10] The use of advance imaging technology with multislice computed tomography (MSCT) for anthropological purposes is recently developed. It is a suitable tool for determining sexual dimorphic characteristics in various anatomies area. 3,4,6,11 This study demonstrates the importance of an objective method utilizing radiological technology in human anthropometric determination in order to assist the analysis of sex identi cation.
The mean age of sample in this study was 50.23 ± 14.36 years. Moreover, a study conducted by Kolesova et al, pelvic size difference was associated with changes in age. Age-related changes observed in the study were carried out in linear parameters of pelvic cavity and con rmed the anterior tilt of sacral oor as well as more horizontal sacrum location in accordance to aging. This study also showed that there was no change in pelvic proportion to ischial height in female while the distance of transverse pelvic diameter shortens with age. 7 As it is stated previously, age-related ankylotic processes decreased sacroiliac joints motility and facilitated these changes. 8-10 There were signi cant differences (p < 0.05) on radiologic components measured between male and female except for transverse diameter of the sacral segment (p = 0.180). These signi cant differences nding was similar to other studies in different populations which there were signi cant differences in pelvic measurements between the sexes. 9,11 In a study by Patriquin et al., they demonstrated signi cant sexual dysmorphism in a population study on South Africa. This study reported differences in pelvic size between sexes as well as differences between races. 9 Furthermore, this study shows a signi cant difference in APOD measurement between male and female group. This result is in accordance to a study conducted by Kolesova and Vetra, that there was signi cant difference in APOD measurements of the two sexes. 12 The result obtained from our study provides a lower mean of APOD value than their study, but it is similar in the sense of APOD value for male due to the fact that it has lower mean than female. The measurement of CPID component in this study showed a higher value in female group.
In previous study, male pelvic structure is signi cantly heavier and thicker than female. The male pelvis is also adjusted to t in more massive and sturdy body architecture e.g. the male acetabulum has been designed to t a larger femur. Even though most of pelvic sexual dimorphisms are due to size differences, sex-related shape variations are also very striking and cannot be considered as an allometric differences in body size between both sexes. 13 This variation in shape is indicated by a rounder frame of female pelvis. Sciatic indentation is wider in female rather than those in male. They have larger, shallower, lower, bigger pelvis and larger pelvic inlet and outlet (Pubic bone is longer and curvature degree of pectineal line is greater). Therefore, women's pelvic bones also differ in characteristics related to sacroiliac joints position on the iliac bones. 14 The SPA measurement showed a signi cant difference between male and female group with high correlation strength. This result is in accordance to previous studies which concluded that SPA was the most reliable indicator of pelvic sex. 15 This is also in accordance to a study by Igbigbi and Msamati, who stated that the accuracy of SPA dimensions in determining sex was 94.7% for female and 95.5% for male. 16 Moreover, a similar result is also portrayed in a study by Mostafa, which showed a signi cant difference in SPA measurements between both sexes. 17 Women's growth tend to increase during adolescence, especially in ischium and pubic areas, resulting in a larger pelvic outlet, longer pubic and a blunter SPA. This growth difference is related to sexual dimorphism associated to birth process. 18,19 The TPO measurement showed a signi cant difference in both sexes with high strength of correlation between male and female group. These ndings are in accordance to previous studies which concluded that a signi cant difference was observed in transverse diameter of pelvic midplane and outlet. This could be explained by hormonal effects of pregnancy which result in pubic symphysis softening and pubic bone movement as wide as one cm, as a consequence there was an increase on pelvic diameter. 12,17 The APOD, CPID, LIH, SPA, and TPO were conducted through multivariate analysis using logistic regression in order to nd signi cant variables and generate a formula that might determine a person's sex with high accuracy. The CPID, LIH, and SPA components showed signi cant values in accordance to previous discussion. These three components consistently showed differences in sexual dysmorphism in both sexes, especially SPA served as one of the high scoring factors consistently. This study shows that the estimated values of pelvic measurements using 3D-CT could provide a pelvic model with a formula that has a high accuracy value using CPID, LIH, and SPA values with p = 0.035, p = 0.001 and p = 0.015 respectively. This formula was able to provide a high overall validity (91.05%) with 100% sensitivity for male identi cation and 81.1% speci city for female identi cation. Nevertheless, these results need to be compared with previous studies in which they were able to provide higher validity values that could reach 100%. 3,17 This study has some limitations that it has few data from patients under 30 years of age, therefore multicentric study with more population under 30 years of age is needed to obtain a greater variety of data and produce more accurate formula for sex determination. In addition, an analytical study of previously published studies may be carried out to compare differences the value of pelvic anthropometry of various races and geographic areas.

Conclusion
There were differences on radiometric variable characteristics in pelvic anthropometric study. CPID, LIH, and SPA components are signi cantly showed differences in sexual dysmorphism in both male and female sexes. The regression formula for sex determination in adults using 3D-CT pelvic measurements in RSUD Dr. Soetomo Indonesia provides a pelvic model sex determination using CPID, LIH, and SPA values with higher validity and sensitivity for male identi cation, as well as higher a speci city for female identi cation.

Funding
This study did not receive any speci c grant from funding / sponsorship agencies in the public, commercial, or not-for-pro t sectors.

Competing interests
Rosy Setiawati has no con ict of interest in this study Ika Ruriana has no con ict of interest in this study Prijambodo has no con ict of interest in this study Giuseppe Guglielmi has no con ict of interest in this study

Availability of data and materials
All data generated or analysed during this study are included in this published article