Background

Identification of human bony remains and any other human parts is of great importance not only for legal but also for humanitarian reasons (Zheng et al., 2012), for example in mass disasters or in case of missed persons; when it’s necessary to identify and know the dead, especially for the information of his surviving relatives (Saukko and Knight, 2016). Skeletal remains examined in archeological or forensic scenes may be destroyed due to burial conditions or any other conditions, as disarticulation, scattering, and commingling. Therefore, it is important to develop new methods that help in sex and age identification from a wide range of skeletal parts (Marlow and Pastor, 2011).

Many authors were able to identify sex from measurements taken from the second cervical vertebra at accuracy rates ranged from 70% to 92.9% (Bethard and Seet, 2013; Gama et al., 2015; Torimitsu et al., 2016; Wescott, 2000). Moreover they proved that the second cervical vertebra is a good sex identifier especially when bigger bones are damaged.

Hou et al. (2012) and Yu et al. (2008) proved that the last thoracic vertebra (T12) showed significant sexual difference (Badr El Dine and El Shafei, 2015); they have reached accuracy rates of 90% and 94.2% respectively for sex determination from T12 measurements (linear measurements of vertebral body and processes) (Ramadan et al., 2017). Moreover, different vertebral measurements taken from the first lumbar vertebra (L1) had great role in sex identification at high accuracy rates according to (Zheng et al., 2012); they proved that accuracy rates of five measurements, related to the vertebral body, were more than 80%.

In addition to sexually dimorphic characteristics, Morphological changes of the vertebrae in the form of marginal bony lipping or osteophytes formation, have great role in understanding ageing patterns (Kacar et al., 2016; Snodgrass, 2004). However, moderate to severe degenerative changes begin around age of 50; as lumbar vertebrae still exhibit striations between ages between 24 and 49 years, and may show only mild lipping or macro-porosity, while Vertebrae older than 50 years usually show absence of striations on the vertebral body, moderate to excessive vertebral degeneration, as osteophytes, lipping, and macro-porosity (Smith, 2010). So, it may be of interest to assess how non-pathologic aging effects, independent from degenerative alterations, are reflected on the vertebrae (Ruhli et al., 2005). Although Ruhli and his colleagues reached that only 20% of all taken vertebral measurements demonstrate significant changes by aging, Mavrych et al. (2014) show significant correlations between all dimensions of the vertebral body and age after exclusion of osteophytes. So, the current study tried to assess the effects of normal aging on lumber vertebrae, independently from age-related degenerative changes, using MSCT.

Previous studies have been conducted on Egyptian samples to identify sex from different skeletal elements as talus measurements (Abd-elaleem et al., 2012), hand bones (Eshak et al., 2011), maxillary sinus (Amin and Hassan, 2012), foot and patella (Abdel Moneim et al., 2008), however, no Egyptian studies had been done on the first lumbar vertebra to determine both age and sex. Single study (Badr El Dine and El Shafei, 2015) was conducted for only sex determination from the first lumbar vertebra (L1) among Egyptians; they tested 24 measurements taken from CT of T12 and L1 to evaluate their role in sex identification. Although the same measurements were taken from both vertebrae with the same method, the results showed great difference. For T12; 14 measurements of 24 were significant and sex was predicted at accuracy rate of 93.1, while for L1; only seven measurements of 24 were significant and sex identification accuracy was very low (68%) (Badr El Dine and El Shafei, 2015). For this reason, this study aims to reassess the role of the first lumber (L1) vertebra in sex identification in addition to age estimation which wasn’t tested in the previous study.

Subjects and methods

Aim of the current study

We aim to establish parameters for identification of age and sex for Egyptians based on the first lumbar vertebral measurements.

Subjects

One hundred and twenty-three Egyptian patients were included in the current study; 61 males (their ages between 10 and 64) and 62 females (age between 10 and 60 years). Abdominal Computer tomography (CT) scans were done for those patients in the Department of Radiology in kasralainy faculty of medicine, Cairo University after they gave informed consent. Patients who seek medical advice or treatment in the Cairo university hospitals are usually from low or moderate socioeconomic classes. The vertebrae used were free from any traumatic and pathological diseases. Also we excluded any vertebrae showing moderate to severe degenerative changes, as severe changes may make border distortion and reading errors. Also we aim to evaluate aging role on vertebral measurements independent of degenerative alterations.

This study was conducted after being approved and ethically accepted by the ethical and the scientific committee of kasralainy medical school in University of Cairo.

Methods

By the aid of the software (Syngo VB 42) and imaging machine (SOMATOM 78830, Siemens, made in Germany), scan was adjusted in bone window with sharpness B70 and 1.5 mm slices width to acquire optimum visualization. To minimize measurement errors, majority of images were adjusted to be maximum intensity projection (MIP) images. This mentioned protocol was used identically for all subjects to avoid technical errors.

Fifteen linear vertebral measurements were measured and taken from the first lumbar vertebra (Table 1 and Fig. 1) in the workstation by forensic pathologist after being trained and supervised by senior consultant radiologist. The 15 measurements included; measurements of the body of the vertebrae as (Upper border (end plate) depth (EPDu), Upper border (end plate) width (EPWu), lower border (end plate) depth (EPDl), Height of anterior border of the body of the vertebra (XHA), lower border (end plate) width (EPWl), Height of the posterior border of the body of the vertebra (XHP)); dimensions of vertebral foramen (lenghth (LVF) and width (WVF)); pedicle dimensions (width (PW) and height (PH)); measurements of spinous process (length (SPL) and height (SPH)); transverse process dimensions (diameter (TD) and distance (TDm)) and Vertebral length (VL)). These measurements were adopted from measurements taken by (Zheng et al., 2012) and (Badr El Dine and El Shafei, 2015); with only one difference as they took their measurements from 3 dimensional (3D) images of CT which wasn’t available for us.

Table 1 Description of Measurements taken from first lumbar vertebra (L1)
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Fig. 1
figure 1

Measurements taken from the first lumbar vertebra. a for sagittal images, b for axial images, c for sagittal images at pedicle level while d for coronal images. In (a) image measurements are demonstrated on T12 and L1 due to large number of measurements

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Statistical analysis

Data was collected in excel sheet using Microsoft excel 2010 and the statistical analysis package (SPSS) last version (version 21) was used for the analysis of data. To compare qualitative data, we used Independent T-test, and variables that revealed significant correlation (P < 0.05) with sex were then included and tested in stepwise discriminant function analysis. While for quantitative data Pearson correlation was used and Pearson coefficient was able to describe both correlation direction (positive or negative) and power (weak correlation if <0.5) (moderate correlation from 0.5 and 0.7) (strong correlation if >0.7). Then, factors showing significant association with age were tested in linear regression models (Dawson and Trapp, 2004).

Results

Descriptive statistics of this study showed statistically significant difference between male and female groups (with males larger than females) for all measurements of the first lumbar vertebra except length of the vertebral foramen (LVF) (Table 2).

Table 2 Male and female difference in measurements of L1
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In addition sex can be predicted from L1 measurements using the following equation at accuracy of 84.6%: S = 0.261 ∗ EPWu – 10.789.

If the equation result was more than (zero), the sex is considered male, otherwise sex is female.

Correlation studies proved that significant correlation was found for age and all vertebral dimensions (Table 3) except for some measurements (TD, LVF, TDm and PW). However, these correlations weren’t strong (R < 0.05). Figure 2 shows correlation between age and SPH which is also weak correlation.

Table 3 The correlation between age and L1 measurements
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Fig. 2
figure 2

Correlation between age and SPH of L1

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In addition, the results of the linear regression analysis (Table 4), for the proved significant measurements by bivariate analysis, revealed that age could be estimated from L1 using any of the following models:

Table 4 Linear regression coefficients for age estimation from L1
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Age = −10.685 + 2.452* EPDu.

Age = −10.685 + 0.766* SPH.

Age = −10.685 + 2.155* WVF.

Age = −10.685 + 3.569* XHP.

For this analysis the R2 = 0.471 and the adjusted R2 is 0.348, so again these equations aren’t strong enough to estimate age with high accuracy rates.

Discussion

In the current study, males were significantly larger in means of all measurements of L1 than females except for LVF and the most accurate measurement was EPWu with accuracy of 84.6%. These results were nearly the same as those of Zheng et al. (2012); they also concluded that nearly all measurements were significant larger in males and the most accurate measurement was EPWu, similar to the current study, with sex correction rate of 88.6%.

In accordance, Ostrofsky and Churchill (2015) concluded that South African males were significantly greater than females in most of L1 measurements. Although they used physical osteological examination (POE) of lumbar vertebrae, they reached that EPWu was the most accurate measurement with accuracy of 87.1%. In addition, different L1 measurements were approved by many authors (Table 5) to be statistically higher in males than females.

Table 5 Sex determination studies of first lumbar vertebra
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Pastor (2005) showed that TDm was the most discriminative measurement for sex prediction from L1 with accuracy of 100% which was too high mostly because the sample was very old collection of white immigrant population from the 18th/19th century and method was physical osteological examination (POE). Also he used physical osteological examination (POE) of L1 for two modern samples (black and white), and reached accuracy rate of 85.1% for black using EPD & EPW (mid length not upper or lower border), and 91.8% for white using measurements not included in this study.

Although the study of Badr El Dine & El Shafei (2015) was conducted on Egyptians, they showed that only seven of 24 measurements of L1 were significantly different between males and females with low accuracy rate 68%. They took their measurements from 3D images which was different from this study (2D images were used) but this difference not assumed to make this difference in results as 3D images were used by Zheng et al. (2012) and showed high accuracy, so further studies on larger Egyptian samples are needed and should compare using 2D and 3D images. Moreover, Badr El Dine & El Shafei (2015) reached that EPDu is the most accurate measurement which is different from the current study, may be due to larger number of used measurements.

In contrast, Ruhli et al. (2006) on historic Swiss sample, found that intervertebral foramen widths of L1 was slight greater in females than in males. These results were explained by methodological differences, possible inter-population variations and because the sample was old historic.

New emerging imaging modalities as magnetic resonance imaging (MRI), angiography and computer tomography (CT) allow visualization of nearly all anatomical and pathological structure with good quality and high resolution (Badr El Dine and El Shafei, 2015). Therefore, CT taken measurements are very accurate as caliper measurements of dry bones (Zech et al., 2012).

Although few studies used computer tomography for measurements taking from L1 for sex identification, no study, up to my knowledge, had tested computed tomography role in both sex and age identification from L1 measurements, or any other vertebrae.

Many of the previous studies (Kacar et al., 2016; Smith, 2010; Snodgrass, 2004) tested the role of osteophyte formation in age estimation, while only few studies (Mavrych et al., 2014; Ruhli et al., 2005) that excluded these degenerative changes.

In the current study, after exclusion of sever degenerative changes, significant correlation was found for age and majority of measurements; but unfortunately it was weak correlation, so vertebral measurements of L1 seem not to be useful indicator for age estimation.

In accordance, Ruhli et al. (2005) show low specific aging effect on vertebral shape, after degeneratively caused alterations are excluded. They conducted their study on two samples; modern Swiss and historic European samples using physical osteological examination (POE). They revealed also that significant weak to moderate positive correlation was found for age and aproximatly 20% of measurements (mainly body diameters) of the seventh cervical (C7) vertebra, the first thoracic (T1) vertebra and the first lumbar vertebra, in males of modern sample. In historic samples, males showed nearly the same results of modern sample, while in females, some measurements showed correlation to age in contrast to modern sample. In contrast, Mavrych et al. (2014) proved that, in both males and females, there was significant correlation for all vertebral body measurements and age. This strong correlation can be explained by the bigger sample (1060 vertebrae) and the used age groups (age range 0–90 years divided into 11 age groups).

On the other hand, many researchers (Jankauskas, 1994; Kacar et al., 2016; Siemionow et al., 2011; Snodgrass, 2004; Watanabe and Terazawa, 2006) revealed significant statistical correlation for age and many measurements of different vertebrae. These correlations were due to the effect of vertebral degenerative changes, which is different from this study. Liguoro et al. (1994) concluded that the best age indicator of all cervical vertebral measurements was sagittal body diameter (SBD).

In addition, many studies (Alhadlaq and Al-Maflehi, 2013; Baccetti et al., 2006, 2002; Baidas, 2012; Baptista et al., 2012; Choi et al., 2016; Flores-Mir et al., 2006; Franchi et al., 2000; Mito et al., 2003, 2002; Uysal et al., 2006) revealed that the correlation for age and vertebral body height (using cervical vertebrae lateral radiography) or vertebral volume (using CT of cervical vertebrae), was strong and positive. However, these studies used different methodologies and were conducted on younger ages below 18 in order to detect maturation of cervical vertebrae as an age determination method in juveniles, which wasn’t similar to the current study.

Conclusion

Sex can be estimated from first lumbar vertebrae with reasonable levels of accuracy in legal and humanitarian situations when skeletal remains are incomplete. However, it seems that vertebral measurements of lumbar vertebrae aren’t useful indicator for age estimation with further studies needed on larger samples and on different age groups.