Radiographic analysis of epiphyseal fusion at knee joint to assess likelihood of having attained 18 years of age

Radiological analysis of the epiphyses of the knee joint provides new valuable information, which may be used in combination with these well-established techniques in order to maximise the accuracy in the assessment of age of 18 years. A total of 215 antero-posterior radiographs of the knee was reviewed retrospectively in patients aged between 14 and 24 years old (99 boys, 116 girls). Fusion was scored as stage 1, epiphysis not fused; stage 2, epiphysis is fully ossified and epiphyseal scar is visible; and stage 3, epiphysis is fully ossified and epiphyseal scar is not visible. Scores of 0, 1 and 2 were assigned to stages 1, 2 and 3, respectively. Lastly, the score related to epiphyseal fusion at the knee joint was obtained by adding the three scores of the distal femur, proximal tibia and proximal fibula. Age distribution gradually increased with each score, for both genders. The mean age (±standard error) in each score category varied between genders, but the differences were not significant (p > 0.11). Five tests were performed to discriminate between individuals who were or were not at age 18 years or more, according to the receiver operating curve. For boys, the highest value of accuracy was obtained with score 3, with high sensitivity (Se = 93.33 %) and specificity (Sp = 89.29 %). For girls, it was obtained with score 4, with high accuracy (Acc = 85.86 %). These results indicate that radiographic analysis of the knee is a valuable alternative as a non-invasive method of estimation of 18 years of age.