A pelvic X-ray may make adulthood more likely—but it cannot prove someone is eighteen. This study found that the choice of grading system can sharply change how trustworthy that judgment becomes. When reliable documents are missing, estimating age can affect criminal proceedings, immigration and asylum cases, human trafficking investigations, and civil disputes.

In many legal systems, specific age limits such as fourteen, sixteen, and eighteen years 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 study evaluated changes in the growing edge of the hip bone on pelvic X-rays in living Egyptians. It compared three ways of grading those changes, for general age estimation and especially for deciding whether a person had reached the eighteen-year legal threshold.

The core idea is like watching paint spread across a fence: the growing edge of the hip bone advances in stages, from no visible change to complete joining with the surrounding bone. One grading system divides the hip’s upper edge into four quarters. The stages mark how far the change has progressed, while the final stage means complete joining.

These pelvic images make the central challenge visible: the same gradual bone changes can receive different maturity readings depending on the system used. The stages run from no visible bone formation to complete joining, illustrating why age estimates near adulthood require caution.

The analysis tested how well each grading system separated people aged eighteen or older from those younger than eighteen. The cutoffs were weighted toward specificity because wrongly calling a minor an adult carries greater consequences than making the reverse mistake.

The French version of the grading system showed an earlier change at its next-to-last stage, then rose past ninety-one percent at the final stage in both males and females. At that final stage, the evidence became much stronger for adulthood, with the positive likelihood measure rising sharply in both groups.

The modified KK-MS and French Risser-Fr systems performed significantly better than the United States version at distinguishing adults aged eighteen or older from younger individuals. The two better-performing systems were not significantly different from each other, and each correctly identified about eighty-seven percent of adults while correctly excluding about ninety-five percent of minors.

The modified system at stage four or the French version at stage five indicated roughly a ninety to ninety-one percent likelihood of adulthood, not certainty. The United States version failed at this threshold because about thirty-nine percent of people younger than eighteen had already reached its final stage, making it forensically unreliable despite its sensitivity.

These results should still be interpreted alongside other age indicators, because the finding raises the probability of adulthood rather than establishing it. Adolescent idiopathic scoliosis has been associated with delayed skeletal maturation, so a cohort enriched for scoliosis may not provide neutral iliac crest maturation norms.

The researchers could not reliably determine why every X-ray had been taken, so the findings may not fully represent Egyptians generally and should be interpreted with caution. The better-performing systems identified adulthood with high but imperfect reliability, while the older approach wrongly classified many minors as adults.

In real cases, the X-ray should inform a broader assessment, never decide it alone.