title: The relationship between fractures and DXA measures of BMD in the distal femur of children and adolescents with cerebral palsy or muscular dystrophy.
abstract: Children with limited or no ability to ambulate frequently sustain fragility fractures. Joint contractures, scoliosis, hip dysplasia, and metallic implants often prevent reliable measures of bone mineral density (BMD) in the proximal femur and lumbar spine, where BMD is commonly measured. Further, the relevance of lumbar spine BMD to fracture risk in this population is questionable. In an effort to obtain bone density measures that are both technically feasible and clinically relevant, a technique was developed involving dual-energy X-ray absorptiometry (DXA) measures of the distal femur projected in the lateral plane. The purpose of this study is to test the hypothesis that these new measures of BMD correlate with fractures in children with limited or no ability to ambulate. The relationship between distal femur BMD Z-scores and fracture history was assessed in a cross-sectional study of 619 children aged 6 to 18 years with muscular dystrophy or moderate to severe cerebral palsy compiled from eight centers. There was a strong correlation between fracture history and BMD Z-scores in the distal femur; 35% to 42% of those with BMD Z-scores less than -5 had fractured compared with 13% to 15% of those with BMD Z-scores greater than -1. Risk ratios were 1.06 to 1.15 (95% confidence interval 1.04-1.22), meaning a 6% to 15% increased risk of fracture with each 1.0 decrease in BMD Z-score. In clinical practice, DXA measure of BMD in the distal femur is the technique of choice for the assessment of children with impaired mobility.
authors.affiliation: Department of Orthopaedics, University of North Carolina, Chapel Hill, NC 27599-7055, USA. richard_henderson@med.unc.edu
authors.forename: Richard C
authors.initials: RC
authors.lastname: Henderson
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Berglund
authors.forename: Ryan
authors.initials: R
authors.lastname: May
authors.forename: Babette S
authors.initials: BS
authors.lastname: Zemel
authors.forename: Richard I
authors.initials: RI
authors.lastname: Grossberg
authors.forename: Julie
authors.initials: J
authors.lastname: Johnson
authors.forename: Horacio
authors.initials: H
authors.lastname: Plotkin
authors.forename: Richard D
authors.initials: RD
authors.lastname: Stevenson
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Szalay
authors.forename: Brenda
authors.initials: B
authors.lastname: Wong
authors.forename: Heidi H
authors.initials: HH
authors.lastname: Kecskemethy
authors.forename: H Theodore
authors.initials: HT
authors.lastname: Harcke
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D015519:Bone Density; D002547:Cerebral Palsy / Q000150:complications / Q000000981:diagnostic imaging*; D002648:Child; D019988:Children with Disabilities; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D050723:Fractures, Bone / Q000150:complications / Q000000981:diagnostic imaging* / Q000209:etiology; D006801:Humans; D008297:Male; D009136:Muscular Dystrophies / Q000150:complications / Q000000981:diagnostic imaging*