Purpose or Case Report: For the skeletal age determination, the hand radiography is most widely used and the Risser index has been well described for patients with scoliosis. Our purpose of this study is to assess patterns of skeletal maturation of the triradiate cartilage (TRC) and the posterior acetabular wall (PA) which can be easily assessed on body CT.
Methods & Materials: Pediatric abdomen, pelvis and hip CT scans could show the status of the bony acetabulum and so all these studies were retrieved from our PACS system over the past 12 years. There were a total of 1446 CT examinations and 122 of these were excluded for any conditions that may affect pelvic bone growth.. As a result, a total of 1324 CT examinations in children with the age ranged from six to 16 years were included for this retrospective study. There were 710 CT scans available in boys and 614 CT in girls. The status of the skeletal maturation of the TRC and PA were evaluated by consensus of two observers. The TRC was divided into four grades according to degree of ossification (grade 0, 1, 2, 3). The PA was divided into three grades (grade 0, 1, 2). Each descriptive data were compared between boys and girls. Pearson’s correlation was used for the statistical analysis.
Results: In boys, the ossification centers of TRC first appeared at the center of three flanges (grade 1) at the age of 11 years and grew into three flanges (grade 2) in 12 years, and completed bony fusion (grade 3) in 14 years old. Regarding PA, the ossification began to appear (grade 1) at 12 years of age and completed fusion (grade 2) in 13 years. In girls, TRC maturation was exactly two years earlier than boys revealing grade 1 at the age of nine years, grade 2 in 10 years, and grade 3 in 12 years. Also for PA, grade 1 was seen in 10 years and grade 2 in 11.5 years. The TRC fused within 1 year after closure of PA. There was no asymmetry between right and left side for both TRC and PA. The concordance rate was excellent (r>0.9) between the grades of TRC and PA by means of Pearson’s correlation.
Conclusions: Knowledge of skeletal maturation in the TRC and PA is helpful for assessing growing children and for interpreting body CT scans in order not to confuse normal ossification process for pelvic fractures.