Unexplained fractures in infancy: looking for fragile bones

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REVIEW

Unexplained fractures in infancy: looking for fragile bones
Nick Bishop, Alan Sprigg, Ann Dalton
................................................................................................................................... Arch Dis Child 2007;92:251–256. doi: 10.1136/adc.2006.106120

See end of article for authors’ affiliations ........................ Correspondenceto: Dr N Bishop, Academic Unit of Child Health, University of Sheffield, Sheffield Children’s Hospital, Sheffield S10 2TH, UK; n.j. bishop@sheffield.ac.uk Accepted 13 October 2006 ........................

fracture occurs when the force exerted on a bone exceeds the ability of the bone to absorb the force by deforming. Fractures in children are common—approximately one third of children will havea fracture by 16 years of age, with more boys experiencing fracture than girls.1 This differentiation in fracture risk is apparent from 2 years of age. Before the age of 2 years, fracture incidence is equal and occurs at a rate of approximately 80/10 000 person years. For the UK, therefore, approximately 4800 infants will have a clinically evident fracture before their first birthday each year.Some long-bone fractures may occur at birth2 in association with events such as shoulder dystocia3; skull fractures may occur during forceps4 and ventouse delivery.5 Some may (uncommonly) occur as a result of clearly defined trauma such as road accidents.6 Most, however, fall into the ‘‘unexplained’’ category. This article reviews our current approach to identifying bone disease in the infantpresenting with more than one unexplained fractures, and discusses the recognised disease processes that result in increased bone fragility. The history should include inquiry into specific areas as listed in the box. The two most frequently recognised underlying disease processes causing bone fragility in infancy are metabolic bone disease of prematurity7 and osteogenesis imperfecta, and directedquestioning is appropriate for these conditions. For premature infants, the features commonly associated with fracture are delivery at ,28 weeks of gestation, necrotising enterocolitis, late (.30 days) establishment of full enteral feeds, conjugated hyperbilirubinaemia, chronic lung disease, and use of furosemide.8 9 For a proportion of infants with osteogenesis imperfecta, there will be a familyhistory either of osteogenesis imperfecta itself or of features that suggest osteogenesis imperfecta. The other elements of the history relating to the possibility of non-accidental injury should of course be applied in every case. Clinical examination, in addition to documenting signs of concern with respect to non-accidental injury, should include assessment of the musculoskeletal system, lookingspecifically for the features detailed in the box. Gross bowing of long bones is uncommon in type I osteogenesis imperfecta. Blue sclerae are present in many healthy infants and children without any associated bone disease. Deep blue sclerae persisting beyond 6 months of age should be regarded as potentially significant; Bauze et al10 found that blue sclerae persisted in all their mildly affectedcases. However, many children with a moderately severe form of osteogenesis imperfecta, type IV osteogenesis imperfecta, have white sclerae.11 It is certainly worth examining siblings and parents who may show

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additional features of osteogenesis imperfecta (see box). It is easier to show ligamentous laxity in this older group than in infants.

PATHOPHYSIOLOGY OF BONE DISEASES PRESENTING WITHFRACTURES IN INFANCY
Metabolic bone disease of prematurity Metabolic bone disease of prematurity (also known as osteopenia of prematurity and preterm rickets) is seen in the UK mainly in infants born at ,28 weeks of gestation.7 Fractures occur typically at an age of at least 10 weeks and usually stop before the age of 6 months (uncorrected for gestation). Three reviews of fractures occurring...