J Korean Soc Radiol.  2019 May;80(3):503-512. 10.3348/jksr.2019.80.3.503.

Ossification of the Triradiate Cartilage and Posterior Acetabulum

• Kim SH
• Yoon HK
• Han H
• Cho S
• Seo YK

• KMID: 2454029
• DOI: http://doi.org/10.3348/jksr.2019.80.3.503

Abstract

PURPOSE
This study attempts to evaluate the skeletal maturation patterns of the triradiate cartilage (TRC) and the posterior acetabular wall (PA), which can be easily assessed on body computerized tomography (CT). It also examines the effect of gender and age on ossification of both TRC and PA.
MATERIALS AND METHODS
This retrospective study included a total of 1324 CT scans for children between the ages of 6 and 16 years. Depending on the extent of ossification in each right or left aspect, determined by the consensus of two observers, the TRC and PA scans were categorized into Grades 4 and 3, respectively.
RESULTS
The TRC for boys began to ossify at age 10 and closed completely at 14, while the PA for boys started ossification at age 11 and entirely fused at 13. The ages of ossification center appearance and complete fusion in both TRC and PA for girls were exactly two years earlier than boys. The TRC fused within one year after the closure of the PA.
CONCLUSION
The appearance and closure of the TRC and PA ossification centers show predictable patterns of development, appearance and merger earlier in females than in males. The suggestion is that development and morphogenesis of both TRC and PA ossification centers can be adequately assessed by using 3-dimensional body CT.

MeSH Terms

Acetabulum*
Cartilage*
Child
Consensus
Female
Humans
Male
Morphogenesis
Retrospective Studies
Tomography, X-Ray Computed

Figure

• 

  Fig. 1 TRC grading. Reformed sagittal, abdominal, pelvic CT shows the TRC ossification center (Grade 0–3). A. No ossification in the center of the three flanges of the TRC of the acetabulum. B. The beginning of ossification in the center of the three flanges (ossification center: annotated by blue colored triangle). C. The extension of the three flanges to the ileum, pubis and ischium (ossification center: annotated by the blue colored Y-shape). D. Maturation and complete fusion of the three flanges (arrow). I = ilium, Is = ischium, P = pubis, TRC= triradiate cartilage

• 

  Fig. 2 PA grading. Axial abdominal, pelvic CT shows the PA ossification center (Grade 0–2). A. The entirely cartilaginous posterior wall and the invisible ossification center (arrows) surrounding the posterior column. B. The appearance of irregular ossification (arrows) in the posterior wall. C. The entire osseous posterior wall that has been fused with the posterior column (arrows). PA = posterior acetabular wall

• 

  Fig. 3 Patient demographics (age and gender distribution of the number of CT scans). The total number of CT scans (n = 1324).

• 

  Fig. 4 Chronological age at appearance and closure of the TRC ossification center. The ossification centers of TRC of the boys first appear in the center of the three flanges (G1) at the age of 11 years and grow into three flanges (G2) at age 12, and complete bony fusion (G3) at age 14 (A, B). TRC maturation of the girls is exactly two years earlier than boys, revealing G1 at age 9; G2 at age 10; and G3, at age 12 (C). G0 = Grade 0, G1 = Grade 1, G2 = Grade 2, G3 = Grade 3, TRC= triradiate cartilage

• 

  Fig. 5 Chronological age at appearance and closure of the PA ossification center. The PA of the boys starts to ossify at age 11 and completes fusion at age 13. The PA of the girls G1 is seen at age 10 and G2 at age 11.5 (A–C). G0 = Grade 0, G1 = Grade 1, G2 = Grade 2, PA = posterior acetabular wall

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