Background and aim Children with cerebral palsy (CP) have increased risk for low bone mineral density (BMD). The aim was to explore the difference in BMD between ambulatory and non-ambulatory children with CP and the relationship between vitamin D status and BMD.

Methods Fifty-one children (age range: 8–18 years; 20 girls) with CP participated and had their BMD measured in the lumbar spine (LS) and the distal femur using dual X-ray absorptiometry. Children with GMFCS level I-III were defined as ambulatory (‘walkers’) while children with level IV-V were defined as non-ambulatory (‘non-walkers’). Serum 25-hydroxy-vitamin D (25-OHD) concentrations were measured as an indicator of vitamin D status.

Results Mean BMD z-score was considerably lower at the distal femur than in the LS. Non-walkers had lower mean z-scores (range: -1.7 to -5.4) than walkers (range: -0.8 to -1.5). Among walkers, those with GMFCS level II had lower BMD z-scores than children with level I at the distal femur (p-values < 0.004) but not in the LS (p = 0.06). Mean 25-OHD concentration was 45 nmol/L (SD: 18); lower in walkers (mean: 41 nmol/L; SD: 18) than in non-walkers (mean: 53 nmol/L; SD: 19; p = 0.041). There was no correlations between 25-OHD and BMD.

Conclusions The main predictor of low BMD was the inability to walk. Children with GMFCS level II had considerably lower BMD than children with level I. The majority of the CP children had insufficient vitamin D status; however, no correlation between vitamin D status and BMD was observed.