Sexual dimorphism of the scapula by morphometric analysis in south Indian population

Ashwini Kumar; Mansour A Alghamdi; Thittamaranahalli Muguregowda Honnegowda

doi:10.4103/ijors.ijors_5_19

ORIGINAL ARTICLE

Year : 2021 | Volume : 29 | Issue : 1 | Page : 12-15

Sexual dimorphism of the scapula by morphometric analysis in south Indian population

Ashwini Kumar¹, Mansour A Alghamdi², Thittamaranahalli Muguregowda Honnegowda³
¹ Department of Forensic Medicine and Toxicology, Kasturba Medical College, MAHE, Karnataka, India
² Department of Anatomy, College of Medicine, King Khalid University, Abha, Kingdom of Saudi Arabia, Saudi Arabia
³ Department of Anatomy, Kannur Medical College, Kannur, Kerala, India

Date of Submission	16-Jul-2019
Date of Acceptance	08-Jul-2021
Date of Web Publication	21-Aug-2021

Correspondence Address:
Thittamaranahalli Muguregowda Honnegowda
Department of Anatomy, Kannur Medical College, Kannur 670612, Kerala.
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/ijors.ijors_5_19

Abstract

Background: Forensic anthropology plays a key role in sexual dimorphism. It is possible to establish a profile and identification of the sex of an individual from the available parts of the skeleton. Several bones present dimorphism and have been studied to increase the approach for forensic identification. Objective: We morphometrically evaluated the human scapula and compared the measurements between scapula bone in cadavers of both sex to derive a logistical regression formula for sex determination of the south Indian population. Materials and Methods: Eighty adult scapulae were used in the study. Scapulae were measured in millimeters for 11 parameters with the help of the sliding caliper. Results: The most common shape of glenoid cavity recorded in this study in men and women was pear shape (54.92% and 51.02%) followed by inverted comma shape (31. 49% and 33.73%). The least common shape was oval (13.57% and 15.28). The mean (standard deviation [SD]) of parameters studies in men vs. women: MSH––143.3 ± 10.23 vs. 138.2 ± 11.89 mm; the MSB––105.3 ± 12.45 vs. 93.5 ± 9.23 mm; SpW––120.0 ± 0.81 vs. 104.0 ± 0.95 mm; ACW––87.0 ± 0.58 vs. 80.0 ± 0.53 mm; L2––44.7 ± 0.46 vs. 35.3 ± 0.39 mm; L4–50.5 ± 8.6 vs. 45.3 ± 9.51; L6–60.1 ± 7.71 vs. 56.8 ± 8.55 mm; SI glenoid diameter––37.63 ± 7.58 vs. 35.5 ± 4.75 mm; the anteroposterior glenoid diameter 1––24.50 ± 5.86 vs. 22.5 ± 6.93 mm and the anteroposterior glenoid diameter 2––16.30 ± 2.16 vs. 13.57 ± 5.58 mm; and mean glenoid cavity index was 65.10 ± 8.67% vs. 63.4 ± 9.23%. All parameters measured showed statistically significant values (P < 0.05) for the male scapula. Conclusion: The scapula can potentially be used in medicolegal investigations in terms of sexual dimorphism. Thus, the results of these studies can provide the baseline values increasing the range of options in the forensic investigation in sex determination.

Keywords: Forensic anthropology, morphometry, scapula, sexual dimorphism

How to cite this article:
Kumar A, Alghamdi MA, Honnegowda TM. Sexual dimorphism of the scapula by morphometric analysis in south Indian population. Int J Orthop Surg 2021;29:12-5

How to cite this URL:
Kumar A, Alghamdi MA, Honnegowda TM. Sexual dimorphism of the scapula by morphometric analysis in south Indian population. Int J Orthop Surg [serial online] 2021 [cited 2023 Mar 25];29:12-5. Available from: https://www.ijos.in/text.asp?2021/29/1/12/324278

Introduction

In forensic anthropology and medicolegal cases, sex determination is vital to establish the identity of an individual.^[1] Sexual dimorphism is proving to be a crucial and effective tool resulting in significant success for the investigation and analysis for individual identification.^[2] Furthermore, an increase in interest of studies in forensic anthropology has been noticed toward the identification of ancient populations through bone pieces. For this purpose, several bones of the skeleton such as skull, pelvis, long bones, and sacrum are the bones on which studies have been done to determine the sex.^[3],[4],[5] Similarly, other bones of the skeleton have been progressively tested for sexual diagnosis as it is not always possible to recover the bones from pelvis and skull.^[6]

Scapula, a bone, is a flat bone that lies on the posterolateral aspect of the chest wall over the second to the seventh rib. Its lateral angle bears the glenoid cavity that articulates with the head of the humerus to form the shoulder joint. Several muscles attached to the scapula thereby afford protection making it difficult to fracture, therefore increasing the potential for undamaged scapulae at forensic scenes.^[7] This study was carried out to morphometrically measure the scapula bone that can be used for sex determination among the South Indian population.

Materials and Methods

This was a cross-sectional study, which was carried out on 80 scapulae (40 men and 40 women) from the Department of Anatomy, dry adult human scapulae, Kannur Medical College, Kannur, India. The age of the bones used in the study was not predetermined. Only scapulas in good condition were included and those were damaged, incomplete or without sex identification were excluded.

The following parameters were studied.

Nonmetric parameters

Shape of the glenoid cavity

The tracing of the shape of the glenoid cavity was taken on a white paper with the help of a graphite pencil. Three types of glenoid were found: (a) pear shape, (b) inverted comma shape, and (c) oval shape [Figure 1].

Figure 1: Different shapes of the glenoid cavity: (A) pear shaped, (B) inverted comma shaped, and (C) oval shaped

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Metric parameters

Maximum scapula height (MSH): Maximum distance between the superior and inferior angle.

Maximum scapula breadth (MSB): Distance between the base of the spine and the center of the glenoid cavity.

Spine width (SpW): Distance between the base of the spine and prominent portion of the acromion.

Acromion-coracoid width (ACW): Distance between the ventral portion of the coracoid process and the most dorsal portion of the acromion.

Scapula body width at 2 cm of the lower/inferior angle (L2): distance between the medial and lateral edges from the second-centimeter height of the scapula.

Scapula body width at 4 cm of the lower/inferior angle (L4): the distance between the medial and lateral edges from the fourth-centimeter height of the scapula.

Scapula body width at 6 cm of the lower/inferior angle (L6): the distance between the medial and lateral edges from the sixth-centimeter height of the scapula.

Superior-inferior glenoid diameter (SI): Distance from the inferior point on the glenoid margin to the most prominent point of the supraglenoid tubercle.

Anterior-posterior glenoid diameter 1 (AP-1): Maximum breadth of the articular margin of the glenoid cavity perpendicular to the glenoid cavity height.

Anterior-posterior glenoid diameter 2 (AP-2): Anteroposterior diameter (breadth) of the top half of the glenoid cavity at the mid-point between the superior rim and the mid equator.

Glenoid cavity index (GCI): It was tabulated from the observed values of SI and AP1 of the glenoid cavity. The formula used for calculating the GCI is anteroposterior glenoid diameter 1 × 100 superoinferior glenoid diameters.

Statistical analysis

Collected data were analyzed using the Statistical Package for the Social Sciences software program, version 15.0 (SPSS, Chicago, Illinois). Descriptive statistics were calculated, and a Student’s t test for equal variances was applied to assess the difference between the means of the male versus female groups. A value of P < 0.05 was considered statistically significant.

Results

Descriptive statistics obtained for the nonmetric and metric parameters are shown in [Table 1] and [Table 2], respectively. [Table 1] shows the results of the various shape of glenoid cavity. The very common shape of glenoid cavity recorded in this study in men and women was pear shape (54. 92% and 51.02%) followed by inverted comma shape (31. 49% and 33.73%). The least common shape was oval (13. 59% and 15.28%) [Table 1] and [Figure 2].

Table 1: Different shapes of glenoid cavity

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Table 2: Observations of different parameters of scapula and glenoid cavity

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Figure 2: Morphometric parameters evaluated in scapula

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[Table 2] shows the results of the 11 scapular measurements. There were significant differences between men and women in all parameters except spine width (SpW), L4, L6, AP glenoid diameter 1, and AP glenoid diameter 2. The P-values indicated that MSH, MSB, ACW, and glenoidal index contributed significantly to sexual dimorphism (P < 0.05).

Discussion

Several factors such as sex, age, race, geographical location, and occupation play an important role in human anthropometry.^[8] Pectoral girdle anthropometry plays a significant role in sex prediction and forensic investigation.^[9]

Bainbridge and Genoese^[10] were the first to use the full scapula as sexual dimorphism and reliability was between 84.20 and 99.87%. Machado et al.^[11] developed reliable discriminant equations of 95.5% efficiency and reliability. Similarly, Dabbs^[12] reported 84%–88% accuracy using maximum length of scapula, maximum length of scapular spine, breadth of infraspinous body, height, and breadth of the glenoid fossa. Macaluso Jr.^[13] reported a success rate of 88.3% for area of the glenoid fossa and a success rate of85.8% for glenoid fossa breadth. Scoltz^[9] found that more than 91% accuracy for women and more than 95% accuracy for men. Pimienta^[14] measured variables such as maximum length and width of the glenoid cavity and reached a success rate of 90% reliability for the differentiation of sex. Papaioannou et al.^[15] were able to obtain up to 95.9% accuracy in the given equation, which used the width of the spine beyond the width of the glenoid cavity, as variables for sex determination. Our finding concurs with other studies that found MSH and MSB to be the best parameter for sex determination in different populations. Charisi et al.^[16] consider that the high-protein diet for the Greek male individuals in ancient times with hypertrophy of the scapular muscles in men, which causes greater height, and hence, increased breadth of the scapula could be one of the reasons for male bones exceeding the dimensions of the women. In our study, except for SpW, L4, L6, anteroposterior glenoidal diameters 1 and 2, all other parameters showed a significant difference between men and women, which was similar to other studies on scapula.^[17],[18] The difference may be due to the differential growth rates of two different sex; women reach skeletal maturity at an earlier age than men. In this study, MSH, MSB, acromion-coracoid width, L2, SI glenoidal diameter, and glenoidal index are good discriminants of sex, with MSH, MSB being the best discriminant.

Conclusion

Our findings could be of clinical importance and interest to forensic anthropologists. The baseline values from our study derived for sexual dimorphism of scapula serve as a framework for future studies and measurements of this bone can be useful in cases where other methods are not applicable, increasing the range of options of forensic investigation teams.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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