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INTRODUCTION
Sex determination is the first essential step for positive identification when a decomposed body is recovered. It is essential to identify sex from different bones of the body, other than the skull or pelvis. The humerus has rarely been tapped as a site for sex determination, though it has often demonstrated an even greater accuracy than other long bones such as the femur (Liu, 1989; Kothandaraman et al., 2014). It is an established fact that, standard metrical values derived for sexing the skeleton in one region if applied to the other region may not give 100 % accuracy. Therefore it is imperative to obtain standard metrical values which are specific to a region (Kshirsagar et al., 2009). Therefore, the purpose of this research was to establish osteometric standards for the determination of sex from the humerus in center of Iran.
These recent studies suggest that the skeletal biology of South Africans is different from others and standards based on geographically distant populations like those of North Americans and Europeans may not provide the most reliable results (Steyn & Iscan, 1997, 1998; Iscan & Steyn, 1999). The purpose of this study is to develop discriminant function formulas for determining sex, using commonly taken osteometric dimensions from the humerus of central of Iran (Iranian population). For more information of the different races to be able to obtain reliable results.
MATERIAL AND METHOD
In the present study, 61 adult humruses of known sex (35 males and 26 females) from central Region of Iran were studied. The following measurements were taken.
Length: measured by using the osteometric board.
Epicondylar width: the maximum distance between medial and lateral epicondyles was measured by vernier calliper.
Midshaft circumference: the circumference of the shaft in the middle was measured with the help of a millimeter graph paper.
Vertical diameter of the head: was taken in the plane of the tip of greater tuberosity, as maximum distance between two points on the head of humerus, with the help of vernire calliper.
Humeral aspect ratio (AR): was calculated as humerus width divided by length and then multiplied by 100, so the AR is the humerus width expressed as a percentage of humerus length.
RESULTS
As shown in Table I, means of Maximum of Width / MAX of Length * 100 (the humeral aspect ratio =AR) were 3.47±.31, and the length of humerus 300.75±1.88 mm, and there were means of midshaft circumference was 60.51±.58 mm, and means of epicondylar width was 56.72±4.05 mm, angle of lateral wall was 124.30±16.51 degree, angle of medial wall was 63.45±18.58 degree, angle of medial and lateral wall was 61.04±17.2 degree, maximum of depth was 6.11±.71 mm, maximum of width was 10.06±.10 mm totally.
As shown in Table II the length of humerus ranged from300.50-35.60 mm and mean is 320.07±1.14 mm in male and 260.90-300.40 mm and mean is 280.99±1.05 mm in females. It was observed that the AR for males was 3.40±.29 and 3.56±.32 in females respectively. There were significant differences between means of these parameters in male and female cases (0.05).
As shown in Table II, the epicondylar width of humerus ranged from 48.00-64.00 and means are 58.37±3.46 54 - 69 mm in males and 49-62 mm and 54.51±3.77 mm in females. There were significant differences between means of these parameters in male and female cases (0.001).
As shown in Table II, the midshaft of humerus ranged from 50.70-70.90 mm and mean 60.76±567 mm in males and in females ranged from 50.20-70.10 mm and mean 60.19±.45 mm. There were significant differences between this parameter in male and female cases (0.001).
As shown in Table II, the depth of bicipital groove of humerus ranged from 4.50-7.50 mm and mean was 6.24±74 mm in males and in females ranged from 4.30-7.50 mm and mean was 5.93±.64 mm. There were significant differences between this parameter in male and female cases (0.0029).
As shown in Table III, there were maximum correlations between AR and width of humerus in two sexes (female=0.932**, male=0.922**), and between midshaft circumference and width of humerus in two sexes (female=0.661**, male=0.591**).
As shown in Tables III and IV, the relationship between the characters of humerus bone in men and women investigated separately. As mentioned above, there were relationships between some characters in two sexes, but it is different in the two sexes. But there are three characteristics that can be seen only in a sexual relationship. They include the relationship between A: epi condylar width with AR (0.471**) and B: midshaft circumference with max of length (0.481 **) in men, and the relationship between epi condylar width and max of length (0.511**) in female. From these demarking points, humeri could be identified and sexed correctly.
Table III Correlation of means of parameters of humerus in male.
**. Correlation is significant at the 0.01 level (2-tailed). *. Correlation is significant at the 0.05 level (2-tailed).
DISCUSSION
The existing literature and the sex estimation equations them propose are derived from three different contexts of skeletal remains. The first group consists of human skeletal remains obtained from archaeological excavations. The sex determination of the specimens was estimated by using morphological or visual methods, and then, based on these materials, the sex determination formulas were developed . In the second group, there are the studies focused on dry skeletons, with known sex. The third group consists of radiographic films and the measurements taken from them (Blackless et al. 2000).
For the second group we collected 61 humerus bones from the department of anatomy and measured 10 parameters of these bones that the specifications in the method described above in method and material paragraph.
In this study we found in men positive correlation between AR and epicondylar width (0.471**) and midshaft with length of humerous (0.481**) that don’t have these parameters correlation in female .And conversely we found in female positive correlation between medial and lateral angle with mid shaf t circumference (0.488**) and width of epicondylar and maximum of length ( 0.511**) and medial angle with medial &lateral angle (0.498**)and maximum width with length of humerous (0.512**) that don’t have these parameters correlation in male. This result reflects the difference between men and women humerus bone dry. It was not found in another study, and we may can make this difference clear sexing.
The observations of sexual differences in the various parameters are shown in comparative Tables IIII. We found that all size of parameters of humerus are greater in men than women except AR index (ratio width /length*100). In comparative of various research, our results are similar of sexual differences in the various parameters. Atamtürk et al. (2010) reports length of humerus in male 57.67, 60.17 in right and left respectively. Hughes reports that humerus is wider in males.
In Lokanadham et al. (2013) comparison of length of humerus of his study with other studies to increase the accuracy in the sex determination, the technique of multi variety analysis was applied. It was found that percentage of humeri that could be sexed correctly was increased. In fact 97 % right and 96.5 % left male humeri and 97.5 % right and 91 % left female humeri could be sexed accurately (Lokanadham et al.).
Sex differences in humeral shape are established prior to puberty is supported by various studies in which greater humeral width was seen in prepubertal boys compared to girls (Patil et al., 2011). compared to Singh and et al., found length from age 3 years until the time of pubertal growth acceleration in females (Palacios-Vargas & CastañoMeneses, 2009). According Kranito et al., study proved that men have shorter humerus shaft than women humerus shaft (Kranioti & Michalodimitrakis, 2009). Morphometric of distal segments of humerus is very important because of its sexual dimorphism and humerus is subjected to greater functional stress (Soni et al., 2013). Scan et al. found that the most effective single dimension, as determined by the direct discriminate analysis, was the vertical head diameter in the Chinese (81 % ) and epicondylar breadth in the Japanese and Thai populations 90 % and 93 % respectively (Is¸can et al., 1998). That our results showed that epicondylar breadth is difference in male and female that is similar with their founded. Soni et al. reports the most dimorphic single parameter on the basis of discriminant analysis was epicondylar width, with an accuracy of 80 % in males and 87.5 % in females and the combination of epicondylar width and vertical head diameter of the shaft provided better results, with 85 % accuracy in males and 90 % accuracy in females.
Robinson & Bidmos (2009) got 72-95.5 % accuracy in their study on the skulls and humeri of South Africans. The humeral head diameter was the most common sex discriminator (Robinson & Bidmos). Kranioti & Michalodimitrakis studied 168 left humeri by the Osteometric method and they found 92.3 % accuracy in determining the sex and found that the single most effective (89.9 %) dimension was the vertical head diameter of the humerus. Kranioti & Michalodimitrakis studied 168 left humeri by the Osteometric method and they found 92.3 % accuracy in determining the sex and found that the single most effective (89.9 %) dimension was the vertical head diameter of the humerus. Vance & Steyn (2013) research utilized 608 individuals from South Africa (420 men, 188 women) to conduct a blind nonmetric determination of sex from three features of the distal humerus: olecranon fossa shape, angle of the medial epicondyle, and trochlear extension. With all features combined, black and white South Africans were categorized successfully as either male or female 75.5 % (77 % accuracy rate for females, 74 % accuracy rate for males). This classification rate is lower than what was found in previous studies, but suggests that characteristics of the distal humerus are still quite valuable when estimating skeletal sex. More research is needed to assess reasons for the differential expression of these traits in different populations and to determine whether the method is no population specific (Vance & Steyn; Pendro et al., 2018).
