Poster Presentation 29th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2019

The reliability of dual-energy X-ray absorptiometry measurements of bone mineral density in the later distal femur of children with Cerebral Palsy. (#120)

Camilla P Davenport 1 , Denise K Brookes 2 , Peter SW Davies 3 , Roslyn N Boyd 1 , Kristie L Bell 3 4
  1. Queensland Cerebral Palsy and Rehabilitation Research Centre, The University of Queensland, Brisbane, QLD, Australia
  2. School of Exercise and Nutrition Science, Queensland University of Technology, Brisbane, QLD, Australia
  3. Children's Health Research Centre, The University of Queensland, Brisbane, QLD, Australia
  4. Department of Dietetics and Food Services, Queensland Children's Hospital, Brisbane, QLD, Australia

Background: Poor bone health is common in children with cerebral palsy (CP) with increased risk of sustaining lower limb fractures associated with low bone mineral density (BMD). The lateral distal femur (LDF) is a common site of fracture in children with CP and the reliability of BMD measures of LDF are needed.

Aim: To investigate the reliability and reproducibility of analysing areal bone mineral density (aBMD, g/cm2) measurements of the LDF using dual-energy X-ray absorptiometry (DXA).

Method: DXA was used to acquire aBMD of left and right LDFs in 72 children with CP (48 Male) aged (mean±SD) 9.7±1.1, across Gross Motor Classification (GMFCS) levels I–V. Lateral distal femur scans were separated into three regions of interest (ROI) for analysis, the mean aBMD of the left and right LDFs for each ROI were analysed. A random sample of 20 scans representative of motor severity across (GMFCS) gender and age were selected. ROI analysis was blinded and repeated by the same investigator to determine within-scan intra-rater reliability and by a different investigator to determine within-scan inter-rater reliability. Data analysis utilised intra-class correlation coefficient (ICC), mean-difference (Mdif) and limits of agreement (LOA) 95% Confidence Interval.

Results: Left and right LDF scans of 20 children (13 Male; aged 9.4±1.1; GMFCS I=9; II=6; III=2; IV=1; V=2) were analysed. Excellent inter-rater and intra-rater reliability and agreement was achieved for all three ROI’s: one (ICC ≥0.996; ICC ≥0.992; Mdiff -0.004; Mdiff 0.004; LOAlower-0.020 LOAupper0.012; LOAlower-0.012 LOAupper0.020) two (ICC ≥0.998; ICC ≥0.99; Mdiff -0.001; Mdiff 0.001; LOAlower-0.013 LOAupper0.010; LOAlower-0.010 LOAupper0.013) and three (ICC ≥0.998; ICC ≥0.995; Mdiff -0.001; Mdiff 0.001; LOAlower-0.014 LOAupper0.011; LOAlower-0.011 LOAupper0.014) respectively.

Conclusion: Reliable measurements and good agreement of aBMD were achieved for all regions of the LDF using DXA. These data provide important parameters for determining aBMD in children with CP.