Also, AP radiographs of the hips showed the characteristic long bone metaphyses and epiphyses irregularity as well as widening of the triradiate cartilage of the pelvis, poorly formed acetabulae, and femoral neck beaking (Figure 2).
The acetabulum is usually poorly formed and reveals a widened triradiate cartilage (Figure 2).
The enlargement of the triradiate cartilage and the poorly formed acetabulae are not seen in this disorder.
Eppinger, in 1903, reporting on four similar pelvic specimens, suggested that the deformity resulted from a disturbance of growth affecting the delayed ossification of the triradiate cartilage.
A disturbance of growth may lead to a delay in ossification of the triradiate cartilage.
The converse of this might be the case: abnormal acceleration of epiphyseal ossification in the pelvis replacing the triradiate cartilage with new, vascular and plastic bone that allows molding under weight bearing.
He described a "beaking" of the triradiate cartilage which is at a maximum at eight years of age and which subsequently remodels.
Experiments on rabbits have shown, however, that premature surgical fusion of the triradiate cartilage leads to a thick medial acetabular wall with progression to subluxation of the hip.
In skeletally immature patients, surgical fusion of the triradiate cartilage has been proposed.
It is most likely that delayed ossification rather than early fusion of the triradiate cartilage is responsible.
In the young, skeletally immature patient with progressive secondary protrusio aceabuli, early surgical fusion of the triradiate cartilage with or without valgus intertrochanteric osteotomy is appropriate.
Gepstein R, Weiss RE, Hallel T: Acetabular dysplasia and hip dislocation after selective premature fusion of the triradiate cartilage.