A Study to Estimate Forensic Age by Kreitner and Kellingaus Main Stages Method from Epiphyseal Ossification of the Iliac Crest by Digital Radiography

Abstract

Objectives: 

The objective of this study is to establish the study of radiographs of the iliac crest epiphysis as a possible criterion for forensic age estimation, using Kreitner and Kellingaus main stages and substages method.

Methodology: 

We scanned 157 participants, comprising 92 males and 65 females in the age bracket of 10 and 25, using X-ray in the Indian Bengali population.

Results: 

Minimum, maximum, mean, and standard deviation were defined. Ossification appeared within the age bracket of 14–17 years, and complete bony fusion took place at the 20^th year of life. Intra- and inter-observer agreements were determined by calculating the kappa coefficients.

Conclusion: 

This study can be used for forensic age diagnosis, but its accuracy is limited when the medicolegally significant age of 18 years has to be determined.

INTRODUCTION

In recent times, the importance of age estimation in living persons has increased manifold. Thus, it is of great importance in forensic science as well as in radiology. For this purpose, applied forensic age diagnostics can be used. In case of these methods, the chronological age is determined from the developmental status of the skeleton.[¹²³] In case of murders, accidents, etc., the identification of an individual is of paramount importance to solve the cases of dubious identity. Moreover, for such identification, age determination is an important criterion. In many countries, the important age limit in civil and criminal cases lie between 14 and 21 years of age. Thus, the determination of skeletal age of individuals in this particular age group is of great importance in forensic science.

Due to its comparatively late ossification, the iliac crest epiphysis may be suitable for age determination. Moreover, there are many detailed studies on iliac crest ossification using conventional radiography,[⁴⁵⁶⁷] computed tomography,[⁸] and anthropological methods.[⁹¹⁰¹¹] In radiology and clinical orthopedics, the iliac crest maturation is identified from the conventional radiographs. Although there is a great variation in the data obtained from various different sources, only a few studies address the queries related to forensic science in this regard.[¹²¹³]

Hence, to establish the iliac crest epiphysis as a possible criterion for forensic age estimation, further fundamental studies are required. As no other study on this topic has been conducted till date on the Indian population using this Kreitner and Kellingaus main stages and substages method, we aspire to evaluate the applicability of the method in India. Again, we aim to create a database for the Indian population for further references.

METHODOLOGY

Study subjects

This study was conducted on people visiting the X-ray center of Calcutta National Medical College (CNMC). Ethical clearance was obtained from the Ethics Committee of CNMC, and proper consent was obtained from the study participants; no additional radiation exposure was given to the study participants. The study sample comprised 157 people (92 males and 65 females) aged between 10 and 25 years. The study was conducted over a period of 3 months. Corresponding medical records did not reveal any disease affecting the skeletal development of the patient.

Methods

Within the radiographic image, the region of investigation reaches from the most lateral point of the iliac bone to that medial point where the iliac wing projection crosses the sacral bone. In order to assess the degree of epiphyseal iliac crest ossification, a modified classification scheme after Kreitner et al.[¹⁴] was used. The original four Kreitner stages are commonly applied in medicolegal, anatomical, and radiological studies. For the present study, the stages were modified for the iliac crest epiphysis [Figure 1] as follows:

Figure 1: Radiographs of the pelvis (anterior.posterior) showing ossification stages of the iliac crest epiphysis

• Grade 1: ossification center has not yet ossified
• Grade 2: ossification center has ossified. Epiphyseal cartilage has not ossified
• Grade 3: epiphyseal cartilage has partially ossified
• Grade 4: epiphyseal cartilage has completely ossified.

In addition, for the Stages 2 and 3, subclassification stages modified after Kellinghaus et al.[¹⁵] were defined as follows:

• Stage 2a: the lengthwise epiphyseal measurement is one-third or less compared to the maximal lengthwise measurement of the iliac wing
• Stage 2b: the lengthwise epiphyseal measurement is over one-third and less than two-thirds as compared to the maximal lengthwise measurement of the iliac wing
• Stage 2c: the lengthwise epiphyseal measurement is over two-thirds as compared to the maximal lengthwise measurement of the iliac wing
• Stage 3a: the epiphyseal fusion to the iliac bone is completed in one-third or less
• Stage 3b: the epiphyseal fusion to the iliac bone is completed in over one-third and less than two-thirds
• Stage 3c: the epiphyseal fusion to the iliac bone is completed in over two-thirds.

Statistical analysis

Ossification stage was determined by one examiner (R.B.) to evaluate intra-observer reliability; the author did repeated assessments of the random samples of fifty pelvic radiographs. For interobserver reliability, a second examiner (S.C.) evaluated the same sample. Both examiners were blinded about the age before and during the examination. Cohen's kappa nonparametric test was used to evaluate the intra- and inter-observer agreement. The Statistical Package for the Social Sciences software (version 22, IBM SPSS Statistics for Windows, Version 25.0. Armonk, NY: IBM Corp., USA) was used to analyze the data.

RESULTS

One hundred and fifty-seven pelvic radiographs were studied to assess the skeletal maturity; ossification stage was determined by two observers. Cohen's Kappa statistics showed good intraobserver and good interobserver agreements. Of these cases ranging between 10 and 25 years, 92 were of males and 65 were of females. Table 1 shows descriptive statistics with maximum, minimum, and mean values of age. As shown in Table 2, we can see that ossification center appears (Grade 2a) from the age group of 14–17 years; most cases over the age of 22–25 years were Stage 4 except 3 case. A significant correlation was found between the age and grade of ossification (P < 0.05). From Table 3, we can see that the mean value for the achievement of Grade 2a was 13.63 years in males and 12 years in females; mean value for the achievement of Grade 4 was 20.85 years in males and 20.43 years in females. The analysis of variance test [Table 4] performed on the sample showed a statistical significance value P = 0.00 (P < 0.05). The Welch test and Brown-Forsythe test [Table 5] showed a statistical significance value of P = 0.00 (P < 0.05). The post hoc test is demonstrated in [Table 6] to allow the comparison between the different age groups. The mean difference is found to be statistically significant at 0.05 level for all age groups, except in between the age group of 18–21 years and 22–25 years (P = 0.794).

Table 1: Descriptive statistics of the study participants

Table 2: Cross.tabulation showing the frequency of participants of particular age group with different ossification stages

Table 3: Comparison of age with grade of ossification

Table 4: Tests showing statistical significance in groups

Table 5: Omnibus tests showing the comparison of groups

Table 6: Tests of between.individual effects

DISCUSSION

In 1934, the earliest description of the apophyseal ossification of the iliac crest was published. In that study, the iliac crest epiphyses appeared between 13 and 14 years of age and got fused between 16 and 18 years of age.[¹⁵] This raw data were challenged by the subsequent studies in the next decades. The precise information about patient's bone maturity still remains the main objective as it gives valuable clues to the attending physicians. Diedrichs et al. in their study, in 1998, using the Risser's grading system updated the standard values of ossification stages in case of the iliac crest epiphyses.[⁶] Current studies have found that the iliac crest ossification begins earlier (12^th year in girls and 13^th year in boys) and fuses later (17^th year in girls and 18^th year in boys) due to the acceleration effect. However, these studies which address the suitability of the iliac crest maturation for forensic purposes are very limited in number. Therefore, in the present study, we have aimed to close that scientific gap by means of a radiographic applicable graduation system that is well established in forensic age diagnostics. The images of 157 pelvic radiographs were assessed according to a modified classification and sub-classification scheme of Kreitner et al.[¹⁴] and Kellinghaus et al.,[¹⁶] respectively. As a result, the age minima established within the scope of the study is in females is 12 years and for males is 13 years and maximum for female is 20 years and for male is 21 years.

Our findings are congruent with those of Wittschieber et al.[¹⁷] and Schmidt et al.[¹³] In contrast with the updated research staging done by Diedrichs et al.,[⁶] our study applied a forensically established system. On the other hand, the study done by Wittschieber et al.[¹⁷] found that the mean chronological age of beginning and completion of the iliac crest ossification was 14 and 24 years, respectively. Whereas in our study, the mean age in this regard was 13.62 years in males and 12 years in females. Furthermore, we found that the completion of ossification Stage 4 was 20.84 years in males and 20.43 years in females.

Chowdhuri et al.[¹⁸] performed a similar study on the same population, analyzing the ossification stages according to the American gradation system of Risser's sign. In that study, it was found that that the mean age of achieving Stage 4 (according to the American gradation system) was 16.28 years in case of males and 16.60 years in case of females. However, the grading system of Risser's is hardly comparable to the forensically more suitable grading system used in the current study.

Our study has a more valid comparability with the study done by Webb and Suchey[⁹] in 1985. They used anthropological methods to investigate the iliac crest ossification. The iliac crest bones of 605 male and 254 female Americans in the age range of 11–40 years were analyzed. The four stages used in that study are analogous to the stages used in our study. In that study, Stage 4 was defined as the complete union of the iliac crest. It was first observed at 17 years in boys and 18 years in girls. Whereas, according to the results obtained from our radiographic data, the corresponding ages were 20.85 years in males and 20.43 years in females.

The findings of our study though are congruent to the study done by Coqueugniot and Weaver[¹¹] using 137 Portuguese skeletal remains in the age range of 7–29 years. They observed complete union of the iliac crest ossification at 20 years of age in males and 22 years of age in females. According to our findings, this is similar in case of males, but there is a divergence of 2 years in case of females.

It can be surmised that this divergence of ages in the final ossification of stages shown by different anthropological studies may be explained by the varying nature of pelvic radiographs. Unlike medial clavicular epiphysis and hand bones, the iliac crest epiphysis is larger in size and has an S-shaped structure. This leads to superimposition of the posterior part of the epiphysis with the bone located just behind it. In comparison to anthropological methods in which uncovered skeletal structures are examined directly, radiological methods show earlier fusion of the epiphyses. To address this drawback, the ossification status should be assessed using both anthropological and radiological methods, and a comparative study should be done.

CONCLUSION

In conclusion, it can be said that the apophyseal iliac crest classification done in this study can be used for forensic age diagnosis, but its accuracy is limited when the medicolegally significant age of 18 years has to be determined. Hence, X-ray of the iliac crest is of limited importance, and its value should be reassessed in forensic practice. However, it can be used as adjunctive to with other imaging techniques to give preliminary technique to determine the age in the Indian population.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.