A pelvic X-ray can show advanced bone maturation, but this study finds that even complete iliac crest fusion as early as about sixteen years cannot by itself prove that someone is legally an adult. Accurate age estimation is a challenging question in forensic medicine, pediatric endocrinology, and orthodontic treatment when reliable documentary records are absent.

The issue matters in criminal proceedings, immigration and asylum cases, human trafficking investigations, and civil disputes because legally relevant age thresholds can determine criminal responsibility and legal protection. That is why reliable methods for estimating age in adolescents and young adults are critically required in forensic practice.

The iliac crest apophysis has attracted increasing attention because its ossification and subsequent fusion occur relatively late in skeletal maturation. That timing makes the iliac crest potentially valuable for age estimation in adolescents and young adults.

The Risser sign describes the sequential ossification and fusion of the iliac crest apophysis along the iliac wing, and it exists in the original US version and the French modification. For many years, orthopedic surgeons have used the Risser sign as an indicator of skeletal maturity in adolescent idiopathic scoliosis.

The forensic applicability of iliac crest ossification remains limited by the small number of population-specific studies. Skeletal maturation varies between populations because of genetic, environmental, nutritional, and socioeconomic influences. Therefore, reference standards derived from one population may not be directly applicable to another, creating a need for region-specific investigations.

In Egypt, reaching eighteen marks the transition from childhood to full legal majority and affects criminal responsibility, marriage eligibility, and access to child-protection provisions. Hand and wrist findings, dental development, and the medial clavicular epiphysis have already been used locally for forensic age estimation.

However, no previous research had evaluated iliac crest apophyseal ossification as an age indicator in this population. The study evaluated iliac crest apophyseal ossification on pelvic radiographs in a living Egyptian population using Risser-US, Risser-Fr, and the Kreitner–Kellinghaus modified system.

The evaluation addressed general forensic age estimation and, particularly, whether individuals had reached the critical eighteen-year legal threshold. This retrospective cross-sectional study used digital pelvic radiographs from 288 Egyptians of both sexes, aged between ten and thirty years, from an institutional radiological database.

The radiographs had originally been obtained during assessment and follow-up of individuals undergoing corrective surgery for lower limb deformities and scoliosis. The study protocol was approved by the Ethics Committee of the Faculty of Medicine, Alexandria University, and informed consent was waived because of the retrospective design.

Only subjects with verified chronological age and sex at imaging were considered. Chronological age was verified using birth certificates for individuals aged ten to fourteen point nine years and national identification cards for individuals aged at least fifteen years.

The images also needed adequate diagnostic quality, clear visualization of the iliac crest apophysis, and no technical artifacts that could interfere with assessment. A single observer evaluated all radiographs after training in the selected iliac crest apophyseal staging methods and receiving standardized reference descriptions and images.

Before staging the study sample, the observer completed a calibration exercise using an independent sample of thirty-five images. Staging was based on the degree of apophyseal ossification, progression of fusion, and eventual complete union with the iliac crest.

Three grading systems evaluated the developmental status of iliac crest apophyseal ossification, and two were derived from the Risser sign. Risser-US divides the iliac crest into four equal quarters: stage zero means complete absence of ossification, while stages one through four represent progressive advancement across successive quarters.

Stage five indicates complete fusion of the iliac crest apophysis with the ilium, beginning posteromedially and proceeding to full union. The Kreitner–Kellinghaus modified system classifies maturation into four main stages, ranging from absence of ossification to complete fusion of the apophyseal cartilage.

Stages two and three are further subdivided into substages a, b, and c, based on the relative length of ossification and degree of fusion in relation to the iliac wing. Reading from panels a through g, the radiographs show a visual progression from faint or absent apophyseal ossification to a continuous, fused iliac crest margin.

The later panels also illustrate why the systems can assign different labels to the same radiograph: maturation features that appear nearly complete are still subdivided more finely by the KK–MS. Receiver operating characteristic analysis evaluated the diagnostic performance of the three staging systems for estimating the eighteen-year legal threshold.

The positive class was chronological age at least eighteen years, while the negative class was age below eighteen years. The cutoffs were weighted toward specificity because misclassifying a minor as an adult carries greater consequence than the reverse error in forensic practice.

Because the three systems were applied to the same subjects, pairwise comparisons of area under the curve used DeLong’s test, with statistical significance assessed at p less than zero point zero five. The study analyzed 288 pelvic radiographs: 127 males, or 44.1 percent, and 161 females, or 55.9 percent, with ages ranging from ten to thirty years.

One hundred individuals, or 34.7 percent, were at least eighteen years old. Because all three staging systems were applied to the same radiographs, intersystem concordance was assessed directly. The two Risser systems showed near-perfect agreement, with a weighted kappa of zero point nine five seven and Spearman’s r of zero point nine zero nine.

Figure three plots age against stage for iliac-crest ossification in females and males across the Risser-US, Risser-Fr, and KK–MS systems. All three curves rise as development progresses, with the Risser-US and Risser-Fr trajectories closely aligned between sexes, while KK–MS shows more visible sex-specific separation.

This matters because the final stages correspond to the sharpest upward shift in the reported probability of adulthood, linking radiographic maturity to adult-status assessment. Under Risser-US, the likelihood of being an adult was zero until full maturity at stage five was reached.

At stage five, the probability of being an adult was 67.1 percent for males and 50.5 percent for females. Even at this terminal stage, the positive likelihood ratio remained comparatively modest: 3.040 in males and 2.333 in females. ROC analysis evaluated discrimination of individuals aged at least eighteen years, with 100 in that group and 188 below eighteen years.

KK–MS and Risser-Fr achieved significantly higher area under the curve than Risser-US: zero point nine five six and zero point nine five three, compared with zero point eight zero six. KK–MS achieved 87.0 percent sensitivity, 95.2 percent specificity, and 92.4 percent overall accuracy.

Risser-Fr showed comparable performance, with 87.0 percent sensitivity, 95.7 percent specificity, and 92.7 percent accuracy. Risser-US had markedly lower specificity, at 61.2 percent, and its overall accuracy was only 74.7 percent. Both KK–MS and Risser-Fr had substantially higher positive likelihood ratios than Risser-US, while the negative likelihood ratio was low and similarly precise for KK–MS and Risser-Fr.

Both KK–MS and Risser-Fr were substantially more reliable than Risser-US for estimating the eighteen-year threshold in this population. KK–MS showed a marginally higher area under the curve, while Risser-Fr showed marginally higher specificity and accuracy; neither system was statistically superior to the other.

Figure four shows ROC curves for the Risser-US, Risser-Fr, and modified Kreitner–Kellinghaus systems when predicting whether age is at least eighteen years. Sensitivity is plotted against one minus specificity, with the diagonal representing chance-level discrimination.

The authors identify stage five in the two Risser systems and stage four in KK–MS as the optimal thresholds, making this comparison relevant to distinguishing minors from adults in medicolegal practice. Table eight compares three staging systems for predicting age at least eighteen years.

Risser-US, using stage five, had an AUC of zero point eight zero six, with one-hundred-percent sensitivity but sixty-one point two-percent specificity; Risser-Fr and KK–MS had AUCs of zero point nine five three and zero point nine five six, respectively. Pairwise DeLong testing found significant AUC differences versus Risser-US, but not between Risser-Fr and KK–MS, supporting the table’s relevance to medicolegal adult-age assessment.

The practical use of iliac crest radiographic staging must be weighed against its radiation burden. Unlike physical or dental examination, pelvic radiography exposes the gonads to ionizing radiation, so obtaining it solely for age estimation raises ethical considerations.

In prospective cases, pelvic radiography should not be a first-line method and should be reserved for situations where non-ionizing or lower-dose alternatives are insufficient. For Egyptian radiographs, Risser-Fr and KK–MS distinguished the eighteen-year threshold far better than Risser-US, but these methods raise the probability of adulthood rather than establishing it—and pelvic radiation limits their routine use.