Accuracies of discriminant function equations for sex estimation using long bones of upper extremities.

Sex prediction from bone measurements that display sexual dimorphism is one of the most important aspects of forensic anthropology. Some bones like the skull and pelvis display distinct morphological traits that are based on shape. These morphological traits which are sexually dimorphic across different population groups have been shown to provide an acceptably high degree of accuracy in the prediction of sex. A sample of 100 patella of Mixed Ancestry South Africans (MASA) was collected from the Dart collection. Six parameters: maximum height (maxh), maximum breadth (maxw), maximum thickness (maxt), the height of articular facet (haf), lateral articular facet breadth (lafb), and medial articular facet breath (mafb) were used in this study. Stepwise and direct discriminant function analyses were performed for measurements that exhibited significant differences between male and female mean measurements, and the “leave-one-out” approach was used for validation. Moreover, we have used eight classical machine learning techniques along with feature ranking techniques to identify the best feature combinations for sex prediction. A stacking machine learning technique was trained and validated to classify the sex of the subject. Here, we have used the top performing three ML classifiers as base learners and the predictions of these models were used as inputs to different machine learning classifiers as meta learners to make the final decision. The measurements of the patella of South Africans are sexually dimorphic and this observation is consistent with previous studies on the patella of different countries. The range of average accuracies obtained for pooled multivariate discriminant function equations is 81.9–84.2%, while the stacking ML technique provides 90.8% accuracy which compares well with those presented for previous studies in other parts of the world. In conclusion, the models proposed in this study from measurements of the patella of different population groups in South Africa are useful resent with reasonably high average accuracies.

Sexual dimorphism is one of the major factors responsible for apparent variations in human skeletal anatomy. Establishing the biological profile of the deceased is essential for personal identification in forensic and archaeological casework. To develop a reliable biological profile, sex allocation is an integral step required to determine age, race/ancestry and stature, given observable differences in aging and growth patterns and variations in morphological traits relating to ancestry. Sex estimation from long bones by visual examination is very difficult. However, metric observations are more objective and effective. This osteometric analysis focused on sex estimation from the femur using discriminant function analysis. Fourteen measurements were taken directly on 175 dry femora (117 males and 58 females), aged 20–60 years, from the Chhattisgarh region of Central India. Student’s t-test was applied to assess significant sex and size differences. Direct and stepwise discriminant function analyses were applied to derive discriminant function models for sex estimation. The three parameters that were selected for the discriminant function analysis included: transverse head diameter, bi-trochanteric distance and maximum shaft diameter. Males were more accurately classified than females. An overall accuracy of 80.6% was reported with direct discriminant function analysis and 76% with stepwise discriminant function analysis upon cross-validation. The transverse head diameter emerged to be the best predictor of sex. This study provides a database and standards for sex estimation from skeletal remains of an unknown nature based on discriminant function equations. This is one of the few studies conducted in India on dry bones, and we anticipate that it will guide forensic specialists in the identification of unknown skeletons from this region.

Metrical and non-metrical assessment of population affinity from the calcaneus

The skull and humerus in the determination of sex: Reliability of discriminant function equations

Sex estimation from skeletal remains is an important practice for forensic human identification. The aims of this study were to assess sexual dimorphism and to develop discriminant function equations for sex estimation using 12 measurements of upper limb bones (humerus, ulna, and radius) in a Thai population. The sample consisted of 228 Thai skeletons (114 males and 114 females) from the Forensic Osteology Research Center, Chiang Mai University, Chiang Mai, Thailand. All skeletal length variables were measured according to the Standards for Data Collection from Human Skeletal Remains. The values of measurements were used to develop the sex estimation equations using univariate and multivariate discriminant function analyses. The results of sexual dimorphism showed that upper limb bone lengths of males were statistically significantly longer than those of females in all dimensions (P<0.05). For univariate discriminant function analysis, the results showed that the epicondylar breadth of the humerus, the physiological length of the ulna, and the antero-posterior diameter at the midshaft of the radius were the best indicators for sex estimation in the humerus, ulna, and radius, respectively. Moreover, the multivariate discriminant function equation using all variables of the ulna and radius was the best indicator for sex estimation. In conclusion, the discriminant function equations derived from upper limb bone measurements provided highly accurate sex estimation in Thai samples. Therefore, these equations using humerus, radius, and ulna measurements can be applied for sex estimation with good accuracy in Thais.

Osteometric sex estimation using the humerus, the radius and the ulna in the contemporary population of Croatia.

Sex estimation is an important aspect of skeletal identification. In addition, previous studies have found that the sex estimation of each race is different. Thus, it is necessary to develop discriminant function equations for the estimation of sex for the Thai population. This study aims to investigate the relationship between width, length and height of the calcaneus and talus with regards to sex and compare the effectiveness of sex estimation between the calcaneus alone, the talus alone, and between both the calcaneus and talus. A total of 200 individuals (100 males and 100 females) were used in this study; ages ranged from 19 to 94 years. Thirteen variables of calcaneus and ten variables of talus were measured. The authors created discriminant function equations for the estimation of sex and tested the efficiency of the equations obtained by using a test group of 40 individuals (20 males and 20 females). By analyzing the mean values of the variables in the calcaneus and the talus, it was shown that males were significantly different from females (p<0.05). Except for the Minimum Inferior Interarticular Distance (MinIID) variable in the left and right talus, the mean of the male and female variables was not significantly different (p>0.05). A stepwise method was used to create 6 equations for sex estimation. The equations were categorized from between the calcaneus alone, the talus alone, and between both the calcaneus and the talus, providing a sex estimation accuracy of between 88.5 and 93.0 %. Using the test group, it was shown that discriminant function equations from the calcaneus alone, the talus alone, and the calcaneus and the talus together, can estimate sex at a high level of accuracy. Sex estimation accuracy was greater than 85 % in all equations. Therefore, the discriminant function equations from the calcaneus alone, the talus alone, and between both the calcaneus and the talus, from this study can be applied to the Thai population.

Sexual dimorphism of the distal femur in a South African computer tomography sample.

An assessment of the accuracy of discriminant function equations for sex determination of the femur and tibia from a South African population

Three-dimensionally derived interlandmark distances for sex estimation in intact and fragmentary crania

Several studies have shown that osteometric differences exist between different population groups. Thus, discriminant function equations derived for the determination of sex from skeletal elements are population specific. In a previous study, the authors derived such equations from nine measurements of the talus of South African whites with high levels of average accuracies. The validity of some of the equations was tested on data collected from a South African black sample that consisted of 120 tali, equally distributed by sex, derived from the Raymond A. Dart Collection of Human Skeletons. The average accuracies dropped significantly. This necessitated the derivation of new equations for the South African black population and the average accuracies obtained ranged between 80% and 89%. The validity of the equations derived from the present study was tested using the leave-one-out classification and two independent samples (1 and 2). The applicability of the equations with very high classification rate from the present study was tested on Independent sample 1 of 10 white tali with poor results. The result of the validity of these equations on an Independent sample 2 of 10 black tali revealed acceptably high average accuracies in correct classification thereby supporting earlier observations on population specificity of discriminant function equations.

Development of discriminant functions to estimate sex in upper limb bones for mixed ancestry South Africans

Fractures of the humerus are common on the midshaft of the bone, often causing injury to the nutrient artery. Successful fracture repair and healing requires preservation of the blood supply to the long bones which is conveyed through the nutrient foramina (NF). The topography of long bone NF varies in different populations. These variations can affect the preservation of blood supply to long bones during fracture repair management. The current study aimed to determine the topography and morphometry of the NF of the humerus in different populations of South Africa including the South African Africans (SAA), South Africans of European descent (SAED), and South Africans of mixed ancestry (SAMA). The study examined 596 dry humerii from the three South African populations, sourced from Raymond A. Dart Collection of Modern Human Skeletons. The parameters examined included the presence, number, location, position, size and direction of the NF, and foramina index (FI). The NF were present in 97.1% of the humerii. Majority of bones (76.8%) evinced a single NF with a diameter equal to or larger than 1.27 mm. The number of NF varied across the different population groups (p = 0.000), with SAA having more humerii presenting with a single NF and SAED having more humerii with two NF. The position of NF varied within and across populations (p = 0.002). Males in SAED had a higher mean FI on both the right (p = 0.030) (effect size = 0.258) and left (p = 0.022) (effect size = 0.421) sides than females. SAED had a lower mean FI than SAMA (p = 0.002) (effect size = 0.384). The location of NF varied across different populations (p = 0.000), with SAA having more NF located on the anteromedial surface and medial border, and SAED having more NF located on the lateral border (p = 0.000). NF were directed towards the distal ends of the shafts in 99.8% of bones and towards the proximal end in 0.2% of bones. The topography and morphometry of the nutrient foramina of the humerus are variable in the South African populations. Knowledge of the NF variations may aid in the management of humerus fractures.

Estimation of sex from scapular measurements using chest CT in Egyptian population sample

The aim of this study was to evaluate the accuracy of sex assessment using measurements of the first rib from computed tomography (CT) to develop a discriminant formula. Four discriminant formulae were derived based on CT imaging of the right first rib of 85 female and 91 male Polish patients of known age and sex. In direct discriminant analysis, the first equation consisted of all first rib variables; the second included measurements of the rib body; the third comprised only two measurements of the sternal end of the first rib. The stepwise method selected the four best variables from all measurements. The discriminant function equation was then tested on a cross-validated group consisting of 23 females and 24 males. The direct discriminant analysis showed that sex assessment was possible in 81.5% of cases in the first group and in 91.5% in the cross-validated group when all variables for the first rib were included. The average accuracy for the original group for rib body and sternal end was 80.9 and 67.9%, respectively. The percentages of correctly assigned individuals for the functions based on the rib body and sternal end in the cross-validated group were 76.6 and 85.0%, respectively. Higher average accuracies were obtained for stepwise discriminant analysis: 83.1% for the original group and 91.2% for the cross-validated group. The exterior edge, anterior-posterior of the sternal end, and depth of the arc were the most reliable parameters. Our results suggest that the first rib is dimorphic and that the described method can be used for sex assessment.