Introduction

Infants and children with metabolic bone diseases are at increased risk of fractures. Demineralization is an observation that alerts the radiologist to the possibility of an underlying disturbance of calcium and phosphorus metabolism. Demineralization or osteopenia are descriptive (qualitative) terms that can be seen in a variety of conditions causing osteoporosis or osteomalacia; for purposes of simplicity, they will be used interchangeably in this chapter (1–4). In osteoporosis there is normal mineralization of physeal cartilage (see Chapters 1 and 2); the demineralization is due to decrease osteoid matrix. However, the diagnosis of osteoporosis in children requires the presence of a clinically significant fracture and low bone mineral content (BMC) and the term “decreased osteoid matrix” is preferred by some (5). Osteomalacia occurs when there is lack of minerals available for adequate mineralization of osteoid matrix and, thus, there is an accumulation of unmineralized bone matrix. Rickets occurs when the endochondral mineralization at the physes is disturbed, leading to the characteristic pathologic and radiographic findings to be described. Rickets is associated with osteomalacia in children; osteomalacia alone is found once the physes have fused (Fig. 8.1).

The most common cause of osteomalacia in children is vitamin D deficiency rickets but there are several other forms of the disease including hypophosphatemic rickets (vitamin D-resistant rickets) and disorders of vitamin D synthesis and/or action. This chapter focuses on osteomalacia and rickets in the infants and young children where the primary manifestations of the metabolic disturbance (metaphyseal irregularities) and superimposed fractures are relevant to the differential diagnosis of abuse. Rickets is also discussed elsewhere in the context of miscellaneous form of abuse and neglect (see Chapter 23).