Pediatric Lateral Distal Femur Reference Ranges for Ages 1 to 18 years

Introduction: Many children with musculoskeletal disorders are at high risk of fracture, and the lateral distal femur (LDF) may be the only feasible site to measure bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA). Pediatric reference ranges and adjustment for linear growth are needed to interpret BMD results.

Methods: Lateral distal femur scans by DXA were obtained on children, ages 1 to 18 y, from two clinical centers. Precision in young children was estimated from duplicate scans. Smoothed reference ranges for three regions of the LDF were generated. Prediction equations were developed to account for the effects of short or tall stature on BMD.

Results: We obtained >2400 measurements on 1,245 children and generated reference ranges for three LDF BMD regions. Precision of BMD was similar (% CV of 1.33 to 2.42 %) to estimates reported at other skeletal sites. Modest sex differences were observed, with females having greater BMD than males at older ages. Children identified as Black had greater BMD than children identified as Non-Black. Height-for-age Z-scores were associated with BMD-for-age Z-scores in pre- and peri-pubertal children, and adjustment equations were generated.

Conclusions: This study fills substantial gaps in pediatric bone health assessment for children with musculoskeletal disorders who are at high-risk of fracture by providing smoothed reference ranges for ages 1 to 18 y and equations to estimate the impact of small body size on BMD-for-age Z-scores.