Low bone mass in patients with motor disability: prevalence and risk factors in 59 Finnish children

Abstract

aBMD Areal bone mineral density BMAD Bone mineral apparent density; DXA Dual-energy X-ray absorptiometry P-ALP Plasma alkaline phosphatase P-Ca Plasma calcium P-Crea Plasma creatinine P-Pi; Plasma phosphate P-PTH Plasma parathyroid hormone S-E2 Serum oestradiol S-FSH Serum follicle stimulating hormone S-LH Serum luteinizing hormone S-Testo Serum testosterone U-Crea Urine creatinine U-Ca Urine calcium S-25-OHD Serum 25-hydroxyvitamin D AIM Children with motor disabilities are at increased risk of compromised bone health. This study evaluated prevalence and risk factors of low bone mass and fractures in these children.METHOD This cross-sectional cohort study evaluated bone health in 59 children (38 males, 21females; median age 10y 11mo) with motor disability (Gross Motor Function Classification System levels II-V). Bone mineral density (BMD) in the lumbar spine was measured with dual-energy X-ray absorptiometry; BMD values were corrected for bone size (bone mineral apparent density [BMAD]) and skeletal maturity, and compared with normative data. Spinal radiographs were obtained to assess vertebral morphology. Blood biochemistry included vitamin D concentration and other parameters of calcium homeostasis.RESULTS Ten children (17%) had sustained in total 14 peripheral fractures; lower-limb fractures predominated. Compression fractures were present in 25%. The median spinal BMAD z-score was )1.0 (range )5.0 to 2.0); it was )0.6 in those without fractures and )1.7 in those with fractures (p=0.004). Vitamin D insufficiency was present in 59% of participants (serum 25-hydroxyvitamin D <50nmol ⁄ l) and hypercalciuria in 27%. Low BMAD z-score and hypercalciuria were independent predictors for fractures.INTERPRETATION Children with motor disability are at high risk of peripheral and vertebral fractures and low BMD. Evaluation of bone health and prevention of osteoporosis should be included in the follow-up.There is increasing evidence that reduced bone mass is associated with increased fracture risk and osteoporosis in chronically ill children. 1 A significant proportion of children with motor disability have low bone mineral density (BMD) and are, therefore, at risk of fracture.2,3 Several risk factors contribute to compromised bone health in these children. Bone loss was earlier considered to be mainly due to reduced weight-bearing activity, but recent studies suggest that the mechanism may be more complex. Many children with motor disability have feeding problems and suboptimal calcium, vitamin D, and other nutrient intakes.2,4 They also tend to have reduced exposure to sunlight and consequently reduced serum concentrations of vitamin D.2,5 Antiepileptic drugs, commonly used by children with cerebral palsy (CP), also cause bone loss. 6Based on our clinical observations, bone fragility is a major clinical problem in children with motor disability. In this study we assessed 59 Finnish children and adolescents with reduced gross motor activity, for clinical, biochemical, and radiological characteristics of bone health. MET...

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