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Abstract
This article reviews the problem of fractures in children and adolescents and some nutritional and other factors that may be involved in the prevention of fractures.
Epidemiology of Forearm Fractures in Children and Adolescents
Building strong bones during childhood and adolescence is important for offsetting the bone loss that naturally occurs later in life and for reducing the risk of osteoporotic fracture. The development of strong bones is also important for the prevention of fractures during childhood and adolescence. Peak bone mass is achieved during the first 2 decades of life, and most of it is acquired in the 2 to 3 years around puberty. Although the highest fracture incidence occurs among the elderly, a second smaller peak in fracture incidence occurs in late childhood and in the beginning of adolescence.1 Fractures are common in children, and approximately 51% of boys and 40% of girls experience 1 or more fractures by 18 years of age.2 The most common fracture site in children is the forearm (24%-26% of all fractures), closely followed by the hands and fingers.2,3 Forearm fractures usually occur in the distal portion of the radius down toward the wrist. Because forearm fractures occur so often, it is important to identify prevention strategies to reduce their occurrence and ensure the bone health of children and adolescents. The pressing need for prevention efforts was recently highlighted by findings that the incidence of forearm fractures in children and young adults has increased substantially over the last 30 years by 32% in males and by 56% in females (Figure 1).4
 | Figure 1. Trends in forearm fracture incidence among residents 35 years or younger in Olmsted County, Minn. Incidence per 100,000 person-years and 95% confidence intervals are shown. Data adapted from Khosla et al. |
Forearm fractures in children are most likely to occur at or slightly before the pubertal growth spurt.1,5 The highest incidence of forearm fractures occurs in boys between 11 and 14 years of age and in girls between 8 and 11 years of age (Figure 2).4 Some speculate that this phenomenon is a consequence of rapid growth and high rates of bone turnover that lead to an increase in bone fragility. During the pubertal growth spurt, there is a slight lag between the rate of linear growth and the rate of mineral acquisition. This is illustrated by the fact that the age at peak height velocity precedes the age of peak bone mineral accretion velocity by approximately 0.7 years.6 Some hypothesize that one consequence of this lag between bone elongation and mineral acquisition is a transient period of relative skeletal fragility. Although the most recognizable change in bones during growth is their longer length, there also are subtle changes in bone shape, and these changes are associated with an increase in bone turnover. Bone turnover is a process in which old bone is first resorbed and then new bone is deposited in the same place. In general, high rates of bone turnover are also associated with increased bone fragility.
 | Figure 2. Incidence of distal forearm fractures among male and female residents of Olmsted County, Minn, from 1999 to 2001, by age group. Taken from Khosla et al. |
Although fractures-especially forearm fractures-are common in children, not all children experience a fracture, as more than 50% of children remain fracture-free throughout childhood and adolescence. Furthermore, some children seem to have a much higher propensity for fracture than do other children. Goulding et al7 prospectively followed 82 girls with a forearm fracture and 88 girls without a previous fracture. Over a 4-year follow-up period, 29% of the girls who had previously experienced a forearm fracture sustained 1 or more additional fractures (primarily of the forearm), whereas only 8% of the girls who were fracture-free at the beginning of the study experienced a fracture during the follow-up period. These findings raise the question as to why some children experience 1 or more fractures whereas other children remain fracture-free. Do children who sustain 1 or more fractures have an increased propensity for injury and falling onto the outstretched forearm? From a biomechanical perspective, fractures occur when the strength of the bone is insufficient to withstand the force applied to it. Therefore, do children with forearm fractures have unusually "weak" bones? Or do they sustain greater forces on their outstretched arm when they fall? In other words, do they fall harder? Or is it a combination of all of the above?
Risk Factors for Falls in Children
Many factors theoretically affect the risk of falling onto the forearm, such as motor ability, balance, and participation in sports or other physical activities. Although very young children who are learning to walk fall frequently, they lack the developmental response to try and catch themselves when they fall; thus, their forearms are spared. We do not know if balance is an important predictor of falls and subsequent forearm fracture among school-aged children and adolescents. The 2 studies that have examined this question produced inconsistent results. One study found that boys with a previous forearm fracture had worse balance than did the boys without a fracture,8 whereas the other study found no association between balance and fracture history.9 With respect to injuries in general, research indicates that motor ability is not a strong predictor of risk of injury.10 A large prospective study of children aged 8 to 12 years found no association between injury risk and reaction time.10 In contrast to expectations, children who had better balance and agility had a greater risk of injury. It may be that as motor ability increases, children take greater physical risks, and these place them at greater risk of injury.
The types of activities in which children choose to participate and the amount of time spent in those activities will also affect the risk of falling and of injury. Playground falls are most common in children between 5 and 9 years of age most likely because they spend the larger amounts of time playing on playgrounds compared with children of other ages.11 Some sports such as soccer, football, and basketball are associated with a high occurrence of falls and fractures. Whether a child or adolescent who spends a lot of time participating in strenuous physical activities is at greater risk of falling and fracturing his or her forearm depends on the type of sporting activities in which they are participating.12 Although strenuous physical activities are the ones that are usually thought of as risk factors for falling and subsequent fracture, 1 study found that boys and girls 9 to 16 years of age with a forearm fracture (n = 190) spent less time in strenuous physical activities and more time watching television than did the boys and girls without a fracture (n = 190).12 It is unknown if this is a reflection of sedentary behavior causing a deterioration of balance and physical skills or whether the fracture resulted in sedentary behavior.
Bone Characteristics and Fracture Risk
Several characteristics of bone affect its strength. Two of the most important and best-studied characteristics in humans are bone material properties and bone geometry (Figure 3). Bone material properties are often estimated by measurement of bone mineral density-the mass (amount) of mineral in a unit volume of bone. Bones with a greater mass or density are stronger than those with less mass or density. Bone geometry includes bone length and cross-sectional dimensions, such as the diameter or width of the bone and the thickness of the cortical shell. Assuming that a bone is cylindrical, a long bone experiences greater strain than a short bone does. The cross-sectional dimensions of bone are important because the location of bone mineral relative to the bending axis affects bone strength. Wide bones are stronger than narrow bones, and bones with a thick cortical shell are stronger than bones with a thin cortical shell. The combination of these 2 characteristics is quantified as the "section modulus." Bones with a greater section modulus are therefore theoretically more resistant to fracture in the presence of bending and torsion forces.
 | Figure 3. Bone characteristics that affect bone strength. |
Goulding and coworkers demonstrated the association between low bone density and forearm fracture in 2 separate studies of children and adolescents in New Zealand. They found that the bone density of the distal radius was lower in boys (3-19 years of age) who had a forearm fracture (n = 100) compared with boys without a fracture (n = 100).13 The deficit in bone density was not restricted to the forearm because bone density at other skeletal sites (eg, lumbar spine and hip) was also lower in boys with a forearm fracture. This research group performed a similar study among 100 girls (3-15 years of age) with a forearm fracture and 100 girls without a fracture.14 Again, they found that the bone density of the distal radius, lumbar spine, hip, and total body was lower in girls with a forearm fracture compared with age-matched girls without a fracture. In both studies, there were no differences in bone area at the measured skeletal sites, indicating that it was the mineral density rather than the bone size that differed between fracture cases and controls. To determine whether the reduced bone density was a transient phenomenon or a persistent characteristic, the investigators followed these girls for another 4 years and remeasured their bone density.15 They found that girls with a previous forearm fracture continued to have lower bone density at all skeletal sites than did the girls who had never experienced a fracture, suggesting that the deficit in bone density was not transient (Figure 4).
 | Figure 4. Ratios with 95% confidence intervals of the relative 4-year gain of bone mineral content at different regional sites in 82 girls with previous fractures compared with those who have never had a fracture (n = 81). Results were adjusted for baseline bone mineral content, and the following variables measured at time 2: bone area, height, weight, and Tanner stage of development. Taken from Jones et al. |
However, other investigators who examined the association between bone density and forearm fracture had different findings. In a case control study by Skaggs and coworkers,16 there was no difference in the bone density of the radius between girls with a distal forearm fracture due to low impact trauma (n = 50) and girls without a fracture (n = 50). These authors measured the bone density of the radius by quantitative computed tomography, which enabled them to measure the density of specific bone types, namely, trabecular bone (woven bone found near the end of long bones) and cortical bone (compact bone, which makes up approximately 85% of the bones in the body), and to measure the cross-sectional geometric dimensions of bone. They failed to find differences in the density of trabecular and cortical bones; however, they found that girls with a distal forearm fracture had a smaller cross-sectional area of the radius (ie, a narrower bone) than did the girls without a fracture. This narrower bone would result in biomechanical disadvantage. Thus, it seems that both low density and narrow bone size increase forearm fracture risk. It is likely that the prevalence of these bone attributes within a given population makes one or the other stand out as etiologically significant.
Dietary Intake and Fracture Risk
Dietary intake, especially of calcium, has important effects on the accrual of bone mass during childhood and adolescence. Suboptimal dietary intake may predispose children to increased risk of fracture due to inadequate bone mass accrual. For instance, one study found that children who habitually avoid milk have a 2.6-fold higher fracture rate than do other children.17 However, low milk or calcium intake has not been found to be associated with risk fractures in other studies.13,14,18,19 This may be because low milk intake was not that common in those studies, and thus, researchers did not identify it as an overarching problem.
Consumption of carbonated beverages has also been associated with increased risk of fracture. In particular, it seems that consumption of colas, but not of other types of carbonated beverages, is associated with the increased risk.18-20 It is possible that cola beverages displace calcium-rich beverages from the diet, that there are components of colas that are deleterious to the bone, or that cola consumption is associated with behaviors that place children at greater risk of fracture. One study found that intake of noncarbonated beverages, mainly fruit juices, was also associated with an increased risk of upper and lower limb fracture.18 The authors speculated that the association of fractures with higher intakes of cola and other beverages was a reflection of the higher hydration needs of physically active children, who, in turn, may be at greater risk of fracture. Others have implicated the relation between cola intake and specific behaviors that affect the risk of fracture as well. Ma and Jones19 found a linear association between cola intake and risk of fracture, as well as time spent viewing television and videos and at the computer. The researchers statistically adjusted for these associations in a multiple regression model. They found that the association between cola intake and forearm fracture was not affected when controlling for milk intake, but it became nonsignificant when controlling for time spent watching television or bone density. Thus, it may be that children who are more sedentary have lower bone mass, which places them at greater risk of fracture, and that cola consumption often occurs during television watching or other sedentary behaviors (Figure 5).
 | Figure 5. Theoretical relationships among television viewing, cola and milk intakes, bone density, and forearm fracture risk. |
Obesity and Forearm Fracture Risk
Excess fatness seems to be associated with an increased risk of forearm fracture. In Goulding's case-control study of boys, those with a forearm fracture had a higher body mass index (kg/m2), percent body fat, and total body fat mass than did the boys without a fracture. Furthermore, boys with a fracture were more likely to be overweight (36% vs 14% were above the 85th percentile of body mass index for age).13 Similarly, a high prevalence of obesity has been found among girls with a forearm fracture.14,16 As is the case for other risk factors, not all studies have found that children and adolescents with a forearm fracture are necessarily more likely to be overweight or obese than children without a fracture.12 Again, this likely reflects that when multiple factors affect the risk of fracture, the relative importance of a given risk factors is population specific.
Three potential reasons have been put forth to explain the relation between obesity and the possible increased risk of forearm fracture in children and adolescents. First is that the force associated with a fall onto the outstretched forearm increases in proportion to body weight. Second, although bone mass generally increases with body size, obese children have decreased bone mass in proportion to their body weight.21 This is because bone mass increases in proportion to muscle or lean mass more than to fat mass. Lastly, the increase in forearm fractures among obese children has been related to decreased balance, which may result in increased risk of injury. In 1 study, obese and nonobese boys aged 10 to 20 years performed a broad variety of physical tests that measured balance and postural sway. They found that obese boys had decreased functional balance compared with nonobese boys.9 It is unknown whether this was a reflection of being "out of practice" or whether their greater weight changed their center of gravity. It is plausible that decreased performance on tests of balance by obese children translates to an increased risk of falling in daily or sporting activities. The combination of a greater force of fall, decreased bone mass in relation to body weight, and a greater risk of falling could place obese children at greater risk of sustaining a forearm fracture than nonobese children.
The relation between obesity and risk of forearm fracture is cause for concern because the increasing prevalence of obesity among children and adolescence may herald a further increase in the incidence of forearm fractures. In fact, the increase in obesity may explain some of the increase in forearm fracture incidence over the last 30 years.4 To further evaluate the importance of obesity in the etiology of forearm fractures, researchers performed a simulation study in which they mathematically modeled the forces on the outstretched arm during a fall and the likelihood of fracture. Obesity was found to have a greater effect on the likelihood of a forearm fracture than did environmental factors, such as the height from which the child fell and the impact surface.22
Fracture Prevention
The high incidence of forearm fractures in children and adolescents results in significant healthcare-related costs, disability, and inconvenience, particularly for children who have repeated fractures. Children who have already sustained 1 fracture are prime candidates for fracture prevention efforts. Multiple strategies will probably be necessary to reduce the incidence of forearm fractures among children and adolescents, including injury prevention, development of stronger bones, and obesity prevention. Diet and physical activity interventions are integral to these.
One injury prevention challenge in youth is balancing the significant beneficial effects of increased physical activity with the increased risk of falling on an outstretched arm. Several randomized trials have shown that increased physical activity, especially weight-bearing activities, is associated with increased bone mass and density in children.23-29 Furthermore, adoption of higher levels of physical activity will be a cornerstone of obesity prevention efforts among the youth. Thus, physical education programs that focus on skill development and balance may result in fewer injuries and, at the same time, provide the opportunity for increased bone loading that may result in increases in bone mass and strength and energy expenditure.
Several randomized controlled trials of calcium supplementation have demonstrated the importance of adequate calcium intake on the development of bone mass and density in children and adolescents.30-34 Ensuring a diet rich in calcium for all children is one way to reduce the risk of forearm fracture. Among adults, there is some evidence that consuming a diet high in calcium may also reduce the risk of obesity and facilitate weight loss. We do not know if this is true for children. Research on other nutritional interventions that may also increase the bone mass and density of the forearm is needed. Because of the high intake of soft drinks by children and adolescents, the relationship between consumption of cola beverages and fracture warrants further investigation to determine whether consumption of cola beverages per se truly increases the risk of forearm fractures. Lastly, dietary interventions to reduce obesity are especially crucial to reduce the risk of forearm fracture and provide many other health benefits.
Unfavorable Blood Fat Levels Predict Rheumatoid Arthritis up to 10 Years Later
A research published in the Annals of Rheumatic Diseases suggests that an unfavorable ratio of blood fats could herald the development of the inflammatory joint disease rheumatoid arthritis up to 10 years later.
The authors based their findings on an analysis of more than 2,000 blood samples donated to a blood bank in the Netherlands. They analyzed the fat content of 1,078 deep-frozen blood samples from 79 people who had given blood between 1984 and 1999 and who subsequently went on to develop rheumatoid arthritis 10 or more years later.
In particular, they looked at the levels of total cholesterol, high-density lipoprotein ("good" cholesterol), triglycerides, apolipoproteins A and B, and lipoprotein(a). The samples were then compared with those taken from 1,071 randomly selected blood donors, matched for age, sex, and storage time. They found that those who subsequently developed rheumatoid arthritis had a more unfavorable balance of circulating blood fats than did those who did not develop the disease. On average, total cholesterol was 4% higher, high-density lipoprotein levels were 9% lower, triglycerides were 17% higher, and apolipoprotein B was 6% higher in those who developed rheumatoid arthritis than in those who did not.
Taken together, these figures also indicate an increased risk of ischemic heart disease, in which the artery walls are thickened and hardened by fat deposits.
The authors state that this might help explain the increased risk of cardiovascular disease among patients with rheumatoid arthritis. They also speculate that a poorer blood fat ratio might make a person more susceptible to inflammation or inflammatory diseases, such as rheumatoid arthritis.
Source: Annals of the Rheumatic Diseases. June 2006.
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