Growth of the acetabular lateral cartilage in relation to congenital and developmental dysplasia of the hip. An histological study.

There are no clear explanations for the spectrum of hip dysplasia nor for the observation that in normal and dysplastic hips, final development may be unpredictable with or without treatment. Immunohistochemical and histological studies of a three month old child's acetabulae were performed. Multiple inclusions were found in the lateral ring epiphysis and in the three flanges of the triradiate cartilage. These inclusions may represent cartilage vessel systems pre-destined to form the secondary centres of ossification. Damage to the primary acetabular growth plates may occur congenitally and help to explain the spectrum of acetabular dysplasia. Damage to one or more of these centres, whether due to instability, displacement or iatrogenic injury, may cause failure of late acetabular development. Hips at risk of damage to the acetabular cartilages should be followed up longer.