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Abstract

Age estimation is one of the most important pillars for identification purposes. The present study aimed to estimate the age of individuals from Prayagraj, Uttar Pradesh, by analyzing radiological images of the sternum obtained through computed tomography (CT) scans. A total of 150 participants (75 males and 75 females) aged between 20 and 70 years were included in the analysis. CT images were systematically examined for the degree of sternal fusion at the manubriosternal and xiphisternal joints, categorized into three stages: no fusion, partial fusion, and complete fusion. The analysis revealed an age-related progression in sternal fusion, with younger individuals exhibiting no fusion, while partial and complete fusion became more prevalent with age. Males demonstrated higher rates of complete fusion compared to females, especially in the xiphoid-body region. Chi-square tests showed a significant correlation between sex and manubrium-body fusion but not body-xiphoid fusion. Regression analysis indicated that manubrium-body fusion accounted for 39.8% of the variance in age. Kruskal–Wallis tests further supported significant differences in median ages across fusion stages. This study highlights the strong correlation between sternal fusion and age, with females generally experiencing earlier fusion. The findings underscore the utility of sternal fusion as a reliable age estimation tool in forensic assessments, considering sex-specific differences in ossification.

Keywords

Personal identification age estimation sternum skeletal remains and computed tomography scans

Introduction

Personal identification establishes and verifies a person’s individuality by using certain features or qualities.¹ Bones play a crucial role in identification, particularly in forensic anthropology cases involving morality and criminals.² When human bodies are discovered, especially if skeletonized, charred, or mutilated bones provide valuable clues for identification.³ Certain human bones exhibit significant sex differences, as these bones display distinct characteristics in males and females.⁴ Typically, the pelvic and cranial bones are used for analysis, but if these are unavailable, the sternum can provide important information about the individual’s age.⁵ In the current world of forensic science, MRI, computed tomography (CT) scans, and X-rays are commonly used to examine bone samples.⁶ Sternum is a long, flat, widened bone situated in the center of the chest, usually called the breastbone.⁷ It is composed of three sections: the manubrium, the body, and the xiphoid process (Figure 1). The present study was planned to use 3D CT images of the sternum of living people whose ages were confirmed from their birth certificates or other legal documents. This study included observation of the fusion of the manubriosternal and xiphisternal joints.

Figure 1.

Parts of the Sternum.

Numerous studies, such as Sahu et al.,⁸ Selthofer et al.,⁹ Ghorbanlou et al.,¹⁰ Ashley,¹¹ Gautam et al.,¹² Singh et al.,¹³ and Silajiya et al.,¹⁴ have estimated age by analyzing the different fusion joints of the sternum (manubriosternal and xiphisternal joints). The main aim of the present study was to ascertain the age of people in the Prayagraj region in Uttar Pradesh by analyzing radiological images of the sternum obtained via CT scans. The findings contribute to the research on age estimation through sternal fusion, offering insights into forensic identification techniques.

Materials and Methods

This prospective study was conducted on individuals who presented to the Kriti Scanning Center for thoracic CT scans undertaken for various medical purposes. Eligible participants were approached, informed about the objectives and procedures of the study, and those who agreed to participate provided written informed consent. Following consent, their CT images were obtained as soft-copy datasets. A total of 150 participants were included in the study, comprising 75 males and 75 females, with ages ranging from 20 to 70 years. The data were collected over a six-month period, from February 2024 to August 2024. The residential identity of each participant was verified through their national identification document (Aadhaar card) to confirm their place of origin.

The CT images were collected in the axial orientation with a slice thickness of 1 mm. Furthermore, sagittal and coronal reformatted images were generated at the workstation for comprehensive evaluation. The scanning was done in the Radiology Department of Kriti Scanning Center, Prayagraj; all patients were scanned using a 384 Multi Detector CT (MD-CT) Scanner. Images obtained have high resolution and have all fine detailing. The images were categorized by age and sex. Five distinct age groups were therefore identified: 30–40 years, 20–30 years, 40–50 years, 50–60 years, and 60–70 years (Table 1).

Table 1.

Showing Division of Samples According to Sex and Age.

Age	20–30 Years	30–40 Years	40–50 Years	50–60 Years	60–70 Years
Male	15	15	15	15	15
Female	15	15	15	15	15

Structural image analysis was performed to estimate age by analyzing the ossification points of the sternum utilizing 3D CT imaging. The measurements were obtained using mouse-driven techniques within the Radiant DICOM viewer software. All CT examinations conformed to a standardized protocol. A single breath-hold was used to scan patients from the thoracic intake to the lung bases. The beam pitch coefficient used for the scans was 1.2, a collimation width of 384 mm, and a scanner rotation time of 0.8 seconds per slice at 120 kV. The relationship between fusion degrees and the assessment of chronological age was conducted through the examination of the manubriosternal and xiphisternal joints. For analysis, different fusion centers were analyzed and categorized according to the fusion between the sternum: Type a: no fusion; Type b: partial fusion and Type c: complete fusion (Figure 2). Statistical analysis was conducted using SPSS software version 20.0, with significance set at a p value of less than .05. Descriptive statistics were employed to demonstrate how fusion occurred over the entire sample. Chi-square tests and regression analyses were performed to investigate the relationships between sternal fusion types, sex, and age. The Kruskal–Wallis test assessed the variations in median ages across the three fusion stages of males and females and pooled samples.

Figure 2.

Fusion Between the Different Parts of the Sternum. (A) No Fusion (Type a); (B) Partial Fusion (Type b); (C) Complete Fusion (Type c).

Result

The findings of the study demonstrate a clear age-related progression in the fusion of both the manubrium–body (M+B) and body–xiphoid (B+XP) joints of the sternum. As shown in Table 2, graphically presented in Figure 3, males exhibited minimal fusion in younger age groups, with fusion gradually increasing in frequency and advancing in stage with age. Older males commonly presented with partial or complete fusion. A similar age-related trend was observed in females Table 3, where early adulthood was characterized by predominantly unfused joints, while advanced age groups demonstrated higher occurrences of partial and complete fusion presented in Figure 4.

Table 2.

Fusion of Sternum, Body and Manubrium in Males.

Age Group	Number of Males	No Fusion (%)	Partial Fusion (%)	Complete Fusion (%)
20–30	15	14	1	0
30–40	15	5	9	1
40–50	15	5	8	2
50–60	15	1	12	2
60–70	15	1	6	8
Total	75	26	36	13

Table 3.

Fusion of Sternum, Body and Manubrium in Females.

Age Group	Number of Females	No Fusion	Partial Fusion	Complete Fusion
20–30	15	14	1	0
30–40	15	5	6	4
40–50	15	0	7	8
50–60	15	0	7	8
60–70	15	0	5	10
Total	75	19	26	30

Figure 3.

Age-wise Comparison of Manubriosternal Joint Fusion Stages in Both Sexes.

Figure 4.

Age-wise Comparison of Xiphisternal Joint Fusion Stages in Both Sexes.

Fusion of the xiphisternal joint (B+XP) also followed a comparable biological progression in both sexes, as summarized in Tables 4 and 5. Younger individuals typically exhibited no fusion, whereas partial and complete fusion became increasingly common with age. Although both sexes showed similar patterns, males tended to display slightly more advanced fusion changes in older age groups.

Chi-Square analysis indicated a significant association between sex and fusion of the manubrium–body joint Table 6, suggesting that males and females differ in the pattern of fusion at this site. However, no significant relationship was observed between sex and the fusion of the body–xiphoid joint Table 7, indicating that xiphisternal fusion progresses similarly in both sexes.

Regression analysis further confirmed a strong positive relationship between age and M+B fusion, establishing fusion stage as an important predictor of chronological age. The Kruskal–Wallis test supported this finding by demonstrating clear differences in age distribution across the three fusion stages. As detailed in Tables 8 and 9, individuals in more advanced fusion stages consistently belonged to older age groups, reinforcing the biological link between sternal fusion and aging.

Overall, the results confirm that sternal fusion progresses systematically with age and that the manubriosternal joint, in particular, holds significant value for age estimation. These findings support the reliability of sternal fusion as a useful parameter in forensic identification.

Table 4.

Fusion of Sternum, Body and Xiphoid Process in Males.

Age Group	Number of Males	No Fusion (%)	Partial Fusion (%)	Complete Fusion (%)
20–30	15	13	2	0
30–40	15	5	7	1
40–50	15	3	10	2
50–60	15	1	8	6
60–70	15	0	6	9
Total	75	14	30	31

Table 5.

Fusion of Sternum Body and Xiphoid Process in Females.

Age Group	Number of Females	No Fusion	Partial Fusion	Complete Fusion
20–30	15	14	1	0
30–40	15	9	5	1
40–50	15	1	9	5
50–60	15	0	8	7
60–70	15	0	6	9
Total	75	24	29	22

Table 6.

Showing a Fusion Stage of the Manubriosternal Joint (M+B).

M+B Fusion Type	Female	Male	Total
CF (complete fusion)	30	13	43
NF (no fusion)	19	26	45
PF (partial fusion)	26	36	62
Total	75	75	150

Table 7.

Showing Fusion Stages of Xiphisternal Joints (X+B).

B+XP Fusion Type	Female	Male	Total
CF (complete fusion)	22	18	40
NF (no fusion)	24	22	46
PF (partial fusion)	29	35	64
Total	75	75	150

Table 8.

Showing Minimum Age, Mean Age and Maximum Age of Fusion of Manubriosternal Joints in Males, Females and Pooled Samples.

Fusion Stage	Gender	Min Age	Mean Age	Max Age
NF	Female	20	34.5	70
	Male	20	35.0	70
	Pooled	20	34.75	70
PF	Female	30	45.5	70
	Male	30	43.0	70
	Pooled	30	44.25	70
CF	Female	33	54.0	70
	Male	39	57.0	70
	Pooled	33	55.5	70

Table 9.

Showing Minimum Age, Mean Age and Maximum Age of Fusion of Xiphisternal Joints in Males, Females and Pooled Samples.

Fusion Stage	Gender	Min Age	Mean Age	Max Age
NF	Female	20	28.5	70
	Male	20	31.3	70
	Pooled	20	29.8	70
PF	Female	30	51.2	70
	Male	30	49.1	70
	Pooled	30	44.25	70
CF	Female	33	56.5	70
	Male	39	59.7	70
	Pooled	33	57.9	70

Discussion

The present study on sternal fusion patterns correlates with some previous studies; major variations exist across populations and should be considered for further study. The current investigation also revealed that sternal fusion occurred considerably later in males than in females, with 60% of the male group aged 60–70 years having united Manubrium and Body (M+B). This pattern is similar to that mentioned by some researchers in their study, who state that among South Indians, sternal fusion begins between the ages of 31 and 35 and lasts until the next age range. According to this research, male fusion happens later, especially within specific ethnic populations.^{13, 15}

There were variations in our findings compared to the current literature on other populations. For example, a study on the Turkish population, using CT imaging, found that manubriosternal fusion begins much earlier, between the ages of 10–19, in both boys and girls.¹⁶ This difference suggests that environmental factors or genetic predispositions may influence sternal fusion across populations. Another study on a Turkish sample also observed earlier fusion, particularly among female participants. These findings support the idea that the timing and process of sternal fusion are not universal and may be shaped by genetic, nutritional, or environmental factors.¹⁷

In terms of sex differences, our results showed that females tend to achieve complete sternal fusion earlier than males. Specifically, 66.67% of females in the 60–70 age group exhibited complete Manubrium and Body (M+B) fusion, compared to 53.33% of males in the same age group. This result aligns with one study that reported earlier sternal fusion in females, particularly in northwest Indian populations.¹³ Similarly, it was observed that females’ complete fusion was noted earlier than males in Turkish populations. These findings suggest a general trend where females reach skeletal maturity earlier than males, though the age at which this occurs can vary across populations.¹⁷

A key observation with significant implications is that the sternal fusion method for forensic age estimation should be calibrated for specific populations. Studies highlight the considerable variation in sternal fusion patterns across different populations. This is also evident in the current study, where the progression of sternal fusion was slower compared to other research. It suggests that factors such as diet, lifestyle, or genetics may influence these differences.^{18, 19}

When comparing fusion in the Body and Xiphoid process (B+XP) region, our study did not find a statistically significant relationship between sex and B+XP fusion types, as indicated by the Chi-Square test (p = .592). This aligns with the observations from Singh & Pathak and Muller et al., where xiphoid-body (B+X) fusion showed more variability and did not demonstrate consistent sex differences.^{13, 18} Radiological and fusion studies have shown strong correlations between sternal fusion patterns and chronological age.^20–22 Morphometric analyses reveal significant sexual dimorphism, aiding in accurate sex identification.²³ Additionally, sternal length and curvature strongly correlate with stature, supporting its anthropometric utility.^{24, 25} This highlights the complexity of using xiphoid fusion as a reliable marker for age estimation and emphasizes the greater utility of manubriosternal fusion in forensic age assessments. Thus. the study, limited to the gross examination, correlates with general trends detected by radiological means and supports sternal fusion as a viable method of estimated age in forensic practice when considering population/sex differential to the same extent, the general trends expressed in various studies underscore the necessity of calibration specific to the given population/sex. From this comparison, it is hoped that future forensic uses of CT scans will incorporate both progress in the field of radiology and a larger-scale database to increase the precision of sternal age assessment even more.

Conclusion

The present study reinforces the significance of sternal fusion, particularly manubriosternal fusion, as a valuable indicator for forensic age estimation. The findings demonstrate that fusion at the manubriosternal joint follows a predictable age-related progression and exhibits meaningful associations with chronological age, emphasizing its utility as a reliable skeletal marker. Although sex-related differences were observed, especially in the pattern of manubriosternal fusion, the xiphisternal joint showed limited predictive relevance, suggesting that not all sternal components contribute equally to age assessment. The study highlights the influence of population-specific variability in sternal fusion patterns. These variations emphasize the need for regionally calibrated standards when interpreting sternal fusion for forensic purposes. Sternal fusion, when analyzed with appropriate consideration of demographic factors, serves as a useful supplementary tool in forensic identification, particularly in cases where conventional skeletal markers are unavailable or compromised. Future research involving larger and more diverse population groups, supported by advanced imaging techniques such as CT, is recommended to further refine and strengthen the applicability of sternal fusion in forensic age estimation.

Footnotes

Abbreviations

CF: Complete fusion

CT: Computed tomography

MDCT: Multidetector computed tomography

MRI: Magnetic resonance imaging

NF: No fusion

PF: Partial fusion

(M+B): Manubriosternal

(X+B): Xiphisternal

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical Approval

The ethical approval LPU/IEC/LPU-IEC/2023/1/2 was collected in December 2023 from the institutional Ethics Committee (IEC) at Lovely Professional University, Phagwara, Punjab.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Informed Consent

Written informed consent was obtained from the participants.

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