Musculoskeletal Imaging

Growth plate

1. Anatomy

the cartilaginous physis or advancing frontier of cellular activity in the endochondral ossification of long bones. This plate or synchondrosis has clearly delimited zones and eventually comes to be located between the epiphysis and diaphysis of tubular bones. The four defined zones of the growth plate include:

  • the reserve zone, in which cartilage cells are few and randomly situated;

  • the proliferating zone, in which matrix is produced and cell proliferation occurs;

  • the hypertrophic zone, which can be subdivided into three other zones (maturation, degeneration, provisional calcification; and

  • the zones of primary and secondary spongiosa.

    Also see bone maturation.

    2. Pathology

    Various conditions may lead to abnormalities in the growth plate (Fig.1). In rickets, the maturation zone shows disorganization with loss of normal columnar pattern and increased numbers of cells; the result is alterations in length and width of the growth plate, decreased calcification, and defective mineralization (Fig.2)

    Premature closure of the growth plate may occur in patients with poliomyelitis, congenital adrenal hyperplasia, Freibergs infraction, Legg Calv Perthes disease, thalassaemia and neuromuscular disorders. Conversely, abnormal widening of the growth plate is seen in some patients with rickets and after radiation therapy.

    In the immature skeleton, the growth plates are especially susceptible to trauma. Physical trauma frequently leads to growth plate injuries from shearing, avulsion, splitting and compressive forces. The zone of hypertrophy is most liable to be affected. Approximately one third of growth plate injuries lead to deformity of growth, sometimes to a significant extent.

    The Salter Harris classification of growth plate injuries categorizes the lesions into five types on the basis of radiographic appearance. Type I represents only separation of the epiphysis and fracture isolated to the growth plate itself (Fig.3); type II is a split in the plate with involvement of the metaphysis and formation of a triangular bone fragment; type III is a vertical fracture that also extends into the epiphysis; type IV represents a fracture involving epiphysis, growth plate and metaphysis; and type V relates to compression of the growth plate that may not be apparent on radiographs. Specific types of injury to the growth plate include slipped capital femoral epiphysis, triplane fractures of the tibia, epiphysiolysis or Little League shoulder syndrome, and chronic stress injuries.

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    Fig.1

    PA radiograph of the wrist in a gymnast demonstrates widening of the distal radial and ulnar physes with adjacent bony sclerosis caused by chronic stress.
    Growth plate, Fig.1
    Growth plate, Fig.2
    Growth plate, Fig.3 (a)
    Growth plate, Fig.3 (b)