Triradiate Cartilage

Fig. 12.1. a AP radiograph in a 5-year-old boy. The triradiate cartilage and the ischio-pubic synchondrosis, have yet to ossify and are seen as radiolucent areas, b AP radiograph in an 8-year-old boy. The ischio-pubic synchondrosis (S) is seen as a prominent area of ossification... 

The triradiate cartilage and ischiopubic synchondrosis may be seen as radiolucent structures or in the older child, it may appear as an area of irregular ossification and this should not be confused with a fracture or bone tumour. Irregular areas of ossification may also be seen around the acetabulum and the iliac crest, which again are features of normal development... 

In view of the relatively small numbers of acetabular injuries that occur in children, developing a classification system is difficult. A classification of injuries to the triradiate cartilage based on the Salter Harris system has been proposed (Heeg et al. 1989). Alternatively, the Judet and Letournel classification, which is widely accepted in adults, may also be used. 

Injury to the triradiate cartilage may be missed on the initial radiograph. Those with less than 2-mm displacement have a good prognosis. 

Hallel T, Salvati EA (1977) Premature closure of the triradiate cartilage. A case report and animal experiment. Clin Orthop Relat Res (124) 278-281 Harley JD, Mack LA, et al. (1982) CT of acetabular fractures comparison with conventional radiography. AJR Am J Roentgenol 138 413-417... 

Harris JH Jr, Lee JS, et al. (2004) Acetabular fractures revisited part 1, redefinition of the Letournel anterior column. AJR Am J Roentgenol 182 1363-1366 Heeg M, Visser JD, et al. (1988) Injuries of the acetabular triradiate cartilage and sacroiliac joint. J Bone Joint Surg Br 70 34-37... 

Late sequelae related to the bony pelvis are more likely to arise from acetabular damage. Severe damage to the triradiate may occur in up to 5% of cases (Bucholz et al. 1982 Heeg et al. 1988,1989). Damage to the cartilage can result in separation and premature closure. Premature fusion will result in abnormal modelling of the acetabulum which may cause subluxation of the femoral head. Long-term complications include anteversion of the femoral neck, repeated subluxation, osteonecrosis and early osteoarthritis (Schlickwei and Keck 2005). 

Bucholz RW, Ezaki M, et al. (1982) Injury to the acetabular triradiate physeal cartilage. J Bone Joint Surg Am 64 600-609... 

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