Introduction

The young skeleton manifests a wide variety of developmental variants that may suggest the possibility of traumatic injury on imaging studies. Additionally, normal osseous structures may project radiographically in a manner that spuriously suggests injury, and in the absence of a history of accidental trauma to explain the findings, abuse may be considered (1). To avoid confusion, the radiologist must be familiar with these vagaries and the features that distinguish them from traumatic injury. This chapter focuses on the developmental variants and misleading images encountered in infancy and early childhood that may mimic inflicted injury. The discussion is not all inclusive and the reader is referred to well-known texts for a broader presentation of normal variations of the developing skeleton (2–4).

Physiologic subperiosteal new bone formation

Physiologic subperiosteal new bone formation (SPNBF) has been long recognized as a normal finding in young infants (5, 6). It involves the femur, humerus, and tibia and less commonly the ulna and radius (Figs. 12.1–12.6). Glaser found SPNBF in 47% of full-term infants and 39% of premature infants undergoing sequential radiographs between 1 and 6 months of age (5). Shopfner noted that the subperiosteal new bone initially produced a hazy, mineralized linear density paralleling an underlying normal cortex (6). With time, this layer of new bone becomes more discretely visible, producing a double contour of the cortex as described (5).