Introduction
Talus is the main tarsal bone that connects bones of the leg with the bones of the foot. It has neither muscular attachments nor tendinous attachments.1 Tracing the origin of the name "Talus" Haliburton RA et al in 1958 recounted that the Roman soldiers made their dice from the heel bones of horses. Hence this heel bone became known as Taxillus, meaning die.2 The articular morphology of the human skeleton is subject to modifications by stresses imposed upon it. A large number of skeletal features have in the past been shown to express sufficient sexual dimorphism to allow accurate identification of sex in skeletonized individuals. In optimum situations when the entire skeleton is present and well preserved and is from a known population, the totality of sexually dimorphic features ensures the correct identification of sex. However, the optimum situation is all too rare. More frequently samples consist of at least some fragmentary or poorly preserved adults in which features of known utility in sex identification are not preserved.3 The purpose here is to address the problem of sex identification in these kinds of remains by using the metric attributes of a tarsal bone – the talus.
Materials and Methods
The materials for the present study consisted of 96 humans dry Tali of unknown age and sex obtained from the Department of Anatomy, Kasturba Medical College, Centre of basic Sciences, Bejai, Mangalore and on X- Rays of 96 healthy normal subjects whose age and sex are known who were referred as patients within the data collection period to the Department of Radiology, Kasturba Medical College, Mangalore.
Study sample size calculation
With 95% Confidence level and 80% Power, a sample size of 96 was calculated by using the formula,
Zα = Level of significance (95%)
Zβ= Required power (80%)
σ= Anticipated standard deviation of the parameter
δ = Test value of the difference between means
Duration
From October 2012 to May 2014 after obtaining the ethical committee approval.
Well preserved dry talus without any distortion and n ormal ankle radiograph were inclusion criteria, Dry Talus having obliterated anatomical landmark and a nkle joint radiograph having Talar and subtalar pathology.
Measurement of dimensions on dry bone
The selected Tali were serially numbered using self-adhesives. The talus was measured using the Osteometric board and Vernier caliper wherever applicable. All the measurements were taken to the nearest millimeter and were converted to centimeter and weight in grams.
The length of the talus- the distance between the foremost parts of the rounded articular surface of the head to the apex of the lateral tubercle4
The Breadth of the talus- the maximum distance between the medial and the lateral surface.4
The Height of the talus- the distance between the superior and inferior surface.4
The Volume of talus- calculated using length* breath* height
Measurements of dimensions on radiograph
The present study was also based on patients between the age of 25 years to 50 years who were scheduled for anteroposterior and lateral plain ankle radiographs because of clinical hindfoot symptoms. All patients without radiological pathologies, fully able to load the foot were included in the study.
The volume of talus- calculated using length* breath* height
On anteroposterior radiograph
The breadth of the body of talus- the distance between the medial and the lateral surface.4
On lateral radiograph
Length of talus- the distance between the foremost parts of the rounded articular surface of the head to the apex of the lateral tubercle.4
Height of talus- the distance between the superior and inferior surface.
Observation and Results
Table 1
Difference between parameters of Talus based on the side (Dry bone)
Table 2
Difference between Parameters of Talus based on the side (Radiograph)
Sex determination of talus (Dry Bone)
Sex determination of dry talus is done based on the demarcating points derived from morphometric measurements of the radiological parameters
Demarcating points
The demarcating points to classify the sex of unknown talus, as male, is derived by using the highest value of demarcating point of female (Mean+3 S.D) and as female is derived by using the lowest value of demarcating point of male (Mean- 3 S.D).5 The Mean ± 3 S.D values for both male and female talus were calculated and demarcating points were derived for X-ray talus as shown in Table 3.
Table 3
Demarcating points of morphometric analysis of Talus for sex determination
By the demarcating point method, only a very few Tali were sexed correctly, 14.58% (14) in dry talus.
Discussion
In a study by Murphy AM in the year 2002 on sex assessment of prehistoric New Zealand Polynesian skeletal remains using talus the accuracy of sex determination ranges from 85.1% to 93.3 %. When the discriminant score is greater than the sectioning point (0.05934) it indicates a male individual and vice versa with an expected accuracy of 93.3%. The single measurement that achieved the greatest discrimination between males and females was maximum length.9
In a study by Harris SM, Case DT (2009)10 on bones of the foot, it was observed that talus on the right side generally exhibited greater dimensions than those from the left side, indicating that the right talus may be more sexually dimorphic than those from the left side and also quoted that greater percentages of correct classifications for length and height dimensions than for width dimensions indicating that length and height measurements to be highly sexually dimorphic. The percentage of correctly classified talus from a total sample of 160 tali varied between 86.6% and 87.6%.11
Sexual dimorphism of talus on dry bone and radiology
The first step for physical anthropologists in analyzing a set of human skeletal remains is to accurately establish the sex of the individual. Accurate sex determinations are not only critical to forensic anthropologists in successfully establishing the identity of unknown individuals, but also to bio-archaeologists in generating demographic information or conducting social analyses of past populations. Therefore, physical anthropologists must have reliable, accurate sexing methods to adequately determine the sex of unknown individuals
By the demarcation method, only 14.4% of talus exhibited sexual dimorphism which is very low could be due to the overlap of many variables in males and females. This low result gives scope and need for detailed study in this subject.
In a study by Lee UY et al the authors observed that the mean value for the size of the male talus is greater than that for females and variables such as Talar length, breadth and height had the highest accuracy for sexing ranging from 72.9% to 86.4%.12
In the present study right, tali exhibited greater dimensions than left except a breadth of the Talus. In a study by Harris SM, Case DT26 they observed that talus on the right side was generally exhibited greater dimensions than those from the left side, indicating that the right Tarsals may be more sexually dimorphic than those from the left side.
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