Evaluation of bone mineral density and bone metabolism in children with multiple bone fractures.
BACKGROUND The aim of the study was to carry out a comprehensive analysis of determinants of multiple bone fractures in children with regard to densitometric indices and markers of bone metabolism. MATERIAL AND METHODS The study involved 112 children aged 5 18 years, including 81 patients with a history of at least 3 bone fractures and 31 healthy patients in a control group. Total body and spinal DXA densitometry of the skeleton (DPX L apparatus, Lunar) was carried out in all children. Laboratory assays comprised the determination of calcium, phosphorus, magnesium (in the serum and 24 hour urine collection) parathormone, liver metabolite of vitamin D, osteocalcin, bone alkaline phosphatase, and N terminal cross linked telopeptide of collagen type I (NTx) RESULTS Mean values of DXA Z score, both in total body and in spinal scans, were significantly lower in children with multiple fractures as compared to controls. In children with multiple fractures, there was a higher prevalence of hypercalciuria, hypermagnesuria and hyperphosphaturia. Decreased levels of the liver metabolite of vitamin D were observed in 20/81 (24.7% patients in this group and in 6/31 controls. Other findings included a higher level of NTx in 38/75 (50.7% patients with fractures, an increased activity of bone alkaline phosphatase in 29, and of osteocalcin in 12 patients. In this group, there was a significant negative correlation between biochemical bone turnover markers and low bone mass. Also, lower DXA Z scores were found in children with higher urinary calcium excretion. CONCLUSIONS 1. Decreased bone mineral density was the most frequent risk factor for bone fractures in children; it was found in about 2/3 of the patients with multiple bone fractures. 2. Accelerated bone turnover, and, particularly, increased bone resorption, indicates a derangement of bone metabolism in children with multiple fractures. 3. Repeated fractures during the body growth period are an indication for a quantitative evaluation of bone mass, calcium phosphate metabolism and bone turnover markers.
Ortopedia, traumatologia, rehabilitacja