Fracture risk in children with a forearm injury is associated with volumetric bone density and cortical area (by peripheral QCT) and areal bone density (by DXA).
Children who sustain a forearm fracture when injured have lower bone density throughout their skeleton, and have a smaller cortical area and a lower strength index in their radius. Odds ratios per SD decrease in bone characteristics measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA) were similar (1.28 to 1.41).


BACKGROUND
Forearm fractures are common in children. Bone strength is affected by bone mineral density (BMD) and bone geometry, including cross-sectional dimensions and distribution of mineral. Our objective was to identify bone characteristics that differed between children who sustained a forearm fracture compared to those who did not fracture when injured.


METHODS
Children (5-16 years) with a forearm fracture (cases, n = 224) and injured controls without fracture (n = 200) were enrolled 28 ± 8 days following injury. Peripheral QCT scans of the radius (4% and 20% sites) were obtained to measure volumetric BMD (vBMD) of total, trabecular and cortical bone compartments, and bone geometry (area, cortical thickness, and strength strain index [SSI]). DXA scans (forearm, spine, and hip) were obtained to measure areal BMD (aBMD) and bone area. Receiver operating characteristic (ROC) analyses were used to assess screening performance of bone measurements.


RESULTS
At the 4% pQCT site, total vBMD, but not trabecular vBMD or bone area, was lower (-3.4%; p = 0.02) in cases than controls. At the 20% site, cases had lower cortical vBMD (-0.9%), cortical area (-2.8%), and SSI (-4.6%) (p < 0.05). aBMD, but not bone area, at the 1/3 radius, spine, and hip were 2.7-3.3% lower for cases (p < 0.01). Odds ratios per 1 SD decrease in bone measures (1.28-1.41) and areas under the ROC curves (0.56-0.59) were similar for all bone measures.


CONCLUSIONS
Low vBMD, aBMD, cortical area, and SSI of the distal radius were associated with an increased fracture risk. Interventions to increase these characteristics are needed to help reduce forearm fracture occurrence.
Kalkwarf
H J
HJ
Division of General and Community Pediatrics, Cincinnati Children's Hospital Medical Center, ML-7035, 3333 Burnet Avenue, Cincinnati, OH 45229, USA. Heidi.Kalkwarf@cchmc.org
Laor
T
T
Bean
J A
JA
D015502:Absorptiometry, Photon; D000293:Adolescent; D015519:Bone Density / Q000502:physiology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D005543:Forearm Injuries / Q000150:complications*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D011884:Radius / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D011885:Radius Fractures / Q000209:etiology*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D014458:Ulna Fractures / Q000209:etiology*