2013 Pediatric Position Development ConferenceFracture Prediction and the Definition of Osteoporosis in Children and Adolescents: The ISCD 2013 Pediatric Official Positions
Introduction
The usefulness of imaging, in particular dual-energy X-ray absorptiometry (DXA), in the assessment of skeletal well-being at all ages is generally accepted, although the ability of DXA alone to predict fracture is limited (1). The effects of variation in body and bone size on DXA measurement of bone mass are covered in the document from Task Force 4, “Reporting Pediatric Densitometry Results.” Fracture frequency is high in children compared with young and middle-aged adults (2), reflecting the interacting effects of bone size and mass, physical activity, and possibly other factors. Among healthy children, as many as half of all boys and a third of girls will fracture by age 18, and one-fifth will have 2 or more fractures 3, 4. Most fractures are of the upper limb; one-third to half of all childhood fractures affect the forearm 2, 5, 6, 7, 8. There is a clear relationship, irrespective of bone mass, between fracture frequency and the overall level of physical activity (9), despite the fact that physical activity and exercise are positively associated with bone mass 10, 11, 12, 13, 14, 15, 16, 17.
In reviewing the existing Positions, the Task Force on fracture prediction and osteoporosis definition collated information from studies that examined the relationship of fracture with a range of factors including genotype, ethnicity, body composition, puberty, antenatal and perinatal events, exercise and physical activity, degree of trauma, diet, and recurrent fractures. With respect to fracture prediction and the definition of osteoporosis, the 2007 Pediatric Position statements are given below, taken from the ISCD Website. Fracture prediction should primarily identify children at risk of clinically significant fractures, such as fracture of long bones in the lower extremities, vertebral compression fractures, or 2 or more long bone fractures of the upper extremities.
The diagnosis of osteoporosis in children and adolescents should not be made on the basis of densitometric criteria alone. The diagnosis of osteoporosis requires the presence of both a clinically significant fracture history and low bone mineral content (BMC) or bone mineral density (BMD). A clinically significant fracture history is one or more of the following:
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Long bone fracture of the lower extremities.
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Vertebral compression fracture.
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Two or more long bone fractures of the upper extremities.
Low BMC or BMD is defined as a BMC or areal BMD Z-score that is less than or equal to −2.0, adjusted for age, gender, and body size, as appropriate.
The approach of the Task Force has been to review the published literature, focusing in particular on articles published since 2007, to provide evidence that either supports the statements as they stand or suggests that they should be amended.
Section snippets
Methodology
Individual task force members were assigned areas of the literature to review and undertook searches using the PubMed and OVID databases from 1966 to 2013. Combinations of terms including those used in the 2007 searches were used (BMD, BMAD, children, adolescents, pediatric, and fracture), along with area-specific terms as indicated previously. Studies were included in the literature set if they included an analysis of the relationship between bone mass/density and fracture. Almost all imaging
Position 1
Fracture prediction should primarily identify children at risk of clinically significant fractures, such as fracture of long bones in the lower extremities, vertebral compression fractures, or 2 or more long bone fractures of the upper extremities. The issue that has arisen in considering this Position is the one relating to degree of trauma in relation to assessment of risk. Given sufficient force, any bone will break. The Task Force agreed that it is thus reasonable to exclude fractures
Summary
The Task Force agreed that excluding fractures occurring as a result of high-energy trauma is appropriate. However, the differentiation of mild and moderate degrees of trauma is difficult to assess; there are few studies where any attempt has been made to rigorously classify trauma, and only Farr's study related degree of trauma to microarchitectural findings. Recall of the exact mechanism of trauma might be difficult; unobserved fractures in younger children would be difficult to classify, and
Position 2
Grade: approve—fair/good—B/C—worldwide.
In the 2007 Position Statements, the second section of the document addressed the question “what are the densitometric criteria for the diagnosis of osteoporosis in a child or adolescent?” We have altered the flow of the document to reflect a more clinical orientation, and this section lays out the new criteria for the diagnosis of osteoporosis. The previous Position 2 was as follows: “The diagnosis of osteoporosis in children and adolescents should not be
Summary of Discussion Regarding the Bone Density Threshold
At present, it is difficult to justify changing the BMD element of the Position, since there are no data to support a change. However, the available data from apparently healthy children indicate that while a lower bone mass for body size is associated with increased fracture risk, children can have fragile bones with an apparently “normal” bone density as assessed by DXA. In discussion in PDC, the idea was put forward that while a BMC/BMD Z-score of ≤−2.0 was required for the diagnosis, this
Effects of Ethnicity
The studies of apparently healthy children relating bone mass to fracture risk have been of predominantly White children. With respect to fracture frequency and ethnicity, data have been presented in 2 studies that indicate a significantly higher risk of fracture for children of White Caucasian origin, as opposed to children of black African origin of similar age, gender, and bone mass. In the studies of Wren et al (24), based on the BMDCS longitudinal cohort study, white boys who subsequently
Future Directions
There was a clear view expressed by Task Force members that a fracture occurring as a result of trivial, mild, simple, or low-energy trauma was more likely to reflect an intrinsic skeletal issue resulting in bone fragility. Work is needed to try and more clearly define what is meant by these terms, however, and in particular to determine whether mild/trivial/simple/low-energy trauma can be readily differentiated from moderate trauma.
The “numbers of fractures by a certain age” element also
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