Quantitative bone analysis in children: current methods and recommendations.

O ver the past decade there have been an increasing number of published manuscripts dealing with pediatric bone mineral density (BMD). The reason for this interest is 2-fold. First, there is a belief that bone gained early in life is an important factor in determining the risk of osteoporosis later in life. Second, there is a desire to identify children who may benefit from drugs that are becoming available for use in treating osteopenia and osteoporosis. Despite the interest, there are several important issues with assessing BMD or the amount of bone (bone mineral content [BMC] or bone mass) that are unique to children that need to be recognized and are discussed in this review. Dual energy x-ray absorptiometry (DXA) is the most common method for assessing BMD and BMC, but other methods, including peripheral quantitative computed tomography (pQCT) and quantitative ultrasonography (QUS), may provide important additional information on bone size, geometry, and quality, and these methods also are discussed. Approximately 90% of adult bone mass is gained in the first 2 decades of life. Optimizing peak bone mass and bone strength early in life and stabilizing it during young adulthood is believed to play a significant role in preventing osteoporosis and fracture later in life. Environmental factors important in determining whether children reach their genetic potential in achieving peak bone mass include adequate nutrition and activity levels. Pediatric diseases, or the therapeutic interventions used in their treatment, also may prevent children from reaching their genetic potential. Diseases or conditions known to affect bone density adversely include osteogenesis imperfecta, gastrointestinal illnesses (ie, inflammatory bowel disease, Crohn’s disease), cystic fibrosis, juvenile rheumatoid arthritis, growth hormone deficiency, chronic steroid use, and history of previous fracture. Obese and less-active children also have been shown to have decreased BMD or bone mass compared with nonobese children of similar weight. Whether this decreased BMD among obese children is a direct effect of fat on bone or due to decreased muscle mass or reduced activity levels, or a combination of both of these factors, is not clear. However, the epidemic of childhood obesity may in part directly or indirectly explain the increase in childhood fracture incidence that has recently been reported. Identifying children with low bone mass early in life could be an important strategy for preventative or therapeutic efforts to optimize bone accrual and, consequently, bone strength.