Musculoskeletal Imaging

Rickets

a bone disorder or group of clinical syndromes resulting from inadequate or delayed mineralization of osteoid in mature cortical and spongy bone, leading to interruption in orderly development and mineralization of the growth plate. Defective mineralization is manifested as rickets in the immature skeleton and as osteomalacia in the mature skeleton. Although rickets and osteomalacia are distinct disorders, prior to growth plate fusion they coexist. The rachitic and osteomalacic syndromes display remarkably similar histologic and radiographic features.

In the growth plate several developmental zones can be identified:

  • reserve zone;

  • proliferating zone;

  • hypertrophic zone, subdivided further into zones of maturation, degeneration and provisional calcification; and

  • zones of primary and secondary spongiosa, located in the metaphysis immediately subjacent to the growth plate.

    In rickets, disorganization in the growth plate and subjacent metaphysis occurs along with defective mineralization and lack of proper formation of bone lamellae and haversian systems.

    General retardation in body growth and osteopenia are observed radiographically. Widening and cupping of the metaphysis results from chaotic cartilage cell growth in the zone of maturation (Fig.1) (Fig.2) (also, see growth plate (III:1), Fig. 2). The presence of bulky growth plates at the shaft bone cartilage junctions of long bones and ribs leads to a rachitic rosary at the costochondral junctions of the middle ribs. Bowing deformity and sabre shin deformity of the tibia also are typical manifestations of rickets. With increasing age scoliosis frequently develops. In addition, the skull shows basilar invagination, and intrusion of the hip and spine into the soft pelvis produces a triradiate configuration. Some of the clinical syndromes related to rickets are listed in Table 1.

    Rickets, Table 1. Clinical syndromes associated with rickets and osteomalacia.

    Vitamin D deficiency rickets
    Gastrointestinal malabsorption
    rickets associated with prematurity
    Hepatic osteodystrophy
    Anticonvulsant drug-related rickets
    Renal osteodystrophy
    Hereditary vitamin D-dependent rickets
    X linked hypophosphataemia
    Tumour-associated rickets
    Hypophosphatasia
    Metaphyseal chondrodysplasia, Schmid type
    Pseudohypoparathyroidism
    Pseudopseudohypoparathyroidism

    DR/RB

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    Fig.1

    AP radiograph demonstrates bowing deformities in the lower extremities. There is widening and cupping of the metaphyses with widened growth plates. (Courtesy of Roger Kerr, MD, Santa Monica, CA)
    Rickets, Fig.1
    Rickets, Fig.2