Skeletal age estimation for forensic purposes: A comparison of GP, TW2 and TW3 methods on an Italian sample

Background: Paediatricians, radiologists, anthropologists and medico-legal specialists are often called as experts in order to provide age estimation (AE) for forensic purposes. The literature recommends performing the X-rays of the left hand and wrist (HW-XR) for skeletal age estimation. The method most frequently employed is the Greulich and Pyle (GP) method. In addition, the so-called bone-specific techniques are also applied including the method of Tanner Whitehouse (TW) in the latest versions TW2 and TW3. Aim: To compare skeletal age and chronological age in a large sample of children and adolescents using GP, TW2 and TW3 methods in order to establish which of these is the most reliable for forensic purposes. Material and methods: The sample consisted of 307 HW-XRs of Italian children or adolescents, 145 females and 162 males aged between 6 and 20 years. The radiographies were scored according to the GP, TW2RUS and TW3RUS methods by one investigator. The results' reliability was assessed using intraclass correlation coefficient. Wilcoxon signed-rank test and Student t-test were performed to search for significant differences between skeletal and chronological ages. Results: The distributions of the differences between estimated and chronological age, by means of boxplots, show how median differences for TW3 and GP methods are generally very close to 0. Hypothesis tests' results were obtained, with respect to the sex, both for the entire group of individuals and people grouped by age. Results show no significant differences among estimated and chronological age for TW3 and, to a lesser extent, GP. The TW2 proved to be the worst of the three methods. Conclusions: Our results support the conclusion that the TW2 method is not reliable for AE for forensic purpose. The GP and TW3 methods have proved to be reliable in males. For females, the best method was found to be TW3. When performing forensic age estimation in subjects around 14 years of age, it could be advisable to use and associate the TW3 and GP methods.