Bone mineral density correlation with fractures in nonambulatory pediatric patients

Although bone mineral density (BMD) as related to T score (comparison with young adult) is well correlated with fracture risk in adults, no such correlation has been confirmed in children. Quadriparetic children have lower BMD than age-matched controls, as well as a higher rate of fragility fracture. This study examines a cohort of children with quadriparesis and other nonambulatory children to correlate BMD with fragility fractures.We hypothesize that fracture in these children is related to BMD as correlated with patient size and that age comparison (Z-score) is less important. Review of all children with a dual-energy x-ray absorptiometry scan from August 2003 to June 2005 identified 101 nonambulatory pediatric patients (excluding children with osteogenesis imperfecta or metabolic bone disease). Sixteen patients had insufficient data, leaving 85 patients, 26 of whom had experienced fragility fractures. Lateral femoral dual-energy x-ray absorptiometry scan was performed on one or both legs, then regions were averaged. Data was evaluated for statistical correlation between BMD and body size as evidenced by body mass index (BMI). Other factors, including age, Z-score, and height and weight independently were secondarily evaluated for correlation with fracture risk. Correlation was demonstrated between history of fracture and BMD when related to BMI (P = 0.002). In conclusion, in these nonambulatory children, the combination of the BMD of the distal femur and BMI correlates well with occurrence of fragility fracture and may relate to fracture risk. This relationship is independent of the child's chronological age and Z-score. This information may be helpful prognostically to define a treatment algorithm for low bone density on a case-by-case basis.