Ianthe E. Jones

More Broken Bones: A 4‐Year Double Cohort Study of Young Girls With and Without Distal Forearm Fractures

Predictors of childhood fractures have not been investigated previously. This study was undertaken to determine whether a previous history of forearm fracture, low bone mineral density (BMD; both areal bone mineral density [aBMD, g/cm2] and volumetric bone mineral apparent density [BMAD, g/cm3]), or anthropometry, influence fracture risk in young girls. At baseline, two cohorts of girls, aged 3–15 years, were evaluated: 100 had recently broken a forearm (group 1) and 100 were fracture free (group 2). Four years later we restudied 170 of these girls (82 from group l and 88 from group 2). We now report the relationships of previous fracture history, baseline BMD (measured by dual‐energy X‐ray absorptiometry), baseline weight, and height to risk of new fracture. More new fractures occurred in group l (37 fractures in 24 girls) than in group 2 (8 fractures in 7 girls; p = 0.0007). The independent predictors for occurrence of a new fracture at any skeletal site in a multivariate model adjusting for age, weight, total body aBMD, and fracture history were previous fracture (hazard ratio [HR], 3.28; 95% CI, 1.41‐7.64); age (HR per l‐year increase, 0.91; 95% CI, 0.84‐0.99); total body aBMD (HR per l SD decrease, 1.92; 95% CI, 1.31‐2.81); and body weight (HR per l SD increase, 1.49; 95% CI, 1.06‐2.08). Girls with two risk factors together had substantially greater fracture risk: previous fracture and low spinal BMAD (HR, 9.4; 95% CI, 2.8‐32.0), previous fracture and high body weight (HR, 10.2; 95% CI, 2.8‐37.6), or previous fracture and low total body aBMD (HR, 13.0; 95% CI, 3.9‐43.1). We conclude that previous forearm fracture, low total body aBMD, low spinal BMAD, and high body weight each increase risk of new fractures within 4 years in young girls. Interventions to reduce the risk of fractures, particularly forearm fractures, in girls warrant further study.

Overweight and obese children have low bone mass and area for their weight

OBJECTIVES: To determine whether girls and boys categorized from body mass index (BMI) values as overweight or obese for their age have lower bone mineral content (BMC) or lower bone area in relation to total body weight than children of normal adiposity.DESIGN: Cross-sectional study in a university bone research unit.SUBJECTS: Two hundred girls and 136 boys aged 3–19 y recruited from the general population by advertisement.MEASUREMENTS: Total body BMC (g) and bone area (cm2) measured by dual energy X-ray absorptiometry (DXA) in relation to body weight (kg), lean tissue mass (kg) and fat mass (kg) in boys and girls of three different BMI percentile groupings: normal weight (BMI<85th percentile); overweight (85 to 94th BMI percentile); obese (≥95th BMI percentile).RESULTS: Obese children had higher BMC, bone area, and fat mass for chronological age than those of normal body weight (P<0.001). In spite of this the observed values for age-adjusted total body BMC and bone area relative to body weight were each lower than predicted values, in both overweight and obese children (2.5–10.1% less, P<0.05) than in children of lower adiposity.CONCLUSION: In overweight and obese boys and girls there is a mismatch between body weight and bone development during growth: their bone mass and bone area are low for their body weight.

Dynamic and static tests of balance and postural sway in boys: effects of previous wrist bone fractures and high adiposity

Ninety-three males aged 10-21 years undertook the Bruininks-Oseretsky balance test and two computerized posturography tests to evaluate the effects of (a) previous forearm fracture and (b) high body weight on balance and postural sway. Body composition was measured by dual energy X-ray absorptiometry. Fracture history did not affect balance measures. However, Bruininks-Oseretsky balance scores were negatively correlated with body weight, body mass index, percentage fat and total fat mass. Overweight subjects (n=25) had lower scores (P<0.05) than boys of healthy weight (n=47), supporting the view that overweight adolescents have poorer balance than those of healthy weight.

How Many Children Remain Fracture-Free During Growth? A Longitudinal Study of Children and Adolescents Participating in the Dunedin Multidisciplinary Health and Development Study

Abstract: While much is known regarding the incidence and pattern of fractures during growth, information is sparse as to how many children fracture repeatedly and how many remain fracture-free during growth. The Dunedin Multidisciplinary Health and Development Study, a birth cohort, whose members were questioned regularly throughout growth (at ages 5, 7, 9, 11, 13, 15 and 18 years) concerning injuries including fractures, has provided a unique opportunity to answer these questions. Life-table analysis showed that approximately half the children remained fracture-free throughout growth [girls 60.1%, (95% CI 54.7–65.0) and boys 49.3% (95% CI 44.0–54.4)]. Data on fracture history, for participants seen at every phase, was available for 601 members through to the age of 18 years (61.1% of the cohort seen at age 5 years). Two hundred and ninety-one of these 601 participants reported 498 fractures, with 172 sustaining a single fracture, and 119 more than one fracture (15.8% girls and 23.4% boys). The most common site of fracture was the wrist/forearm (24.1% of all fractures). We conclude that although bone fractures are a common adverse event in childhood, half of all children remain fracture-free throughout growth.

Spinal Overload: A Concern for Obese Children and Adolescents?

Abstract: Heavy children require stronger bones than leaner children. The present cross-sectional observational study was undertaken to examine the magnitude of compensatory increases in the spinal bone mineral content (BMC) and area shown by overweight and obese children and adolescents. Vertebral area and BMC of lumbar vertebrae L2–L4 were measured by dual-energy X-ray absorptiometry in 202 boys and 160 girls aged 3–19 years. Subjects were categorized as of normal weight, overweight or obese using international cutoffs for body mass index. Compared with children of healthy weight our overweight and obese children had lower vertebral BMC for their bone area, body height, body weight and pubertal development: ratios and 95% CI for overweight and obese groups were 0.92 (95% CI 0.87–0.97) and 0.88 (95% CI 0.80–0.96) for girls and 0.96 (95% CI 0.91–1.02, NS) and 0.87 (95% CI 0.78–0.96) for boys, respectively. Spinal area was low in overweight and obese girls compared with girls of healthy weight but overweight and obese boys had enlarged their vertebral area appropriately for their increased body size. We conclude that during growth overweight and obese children do not increase their spinal BMC to fully compensate for their excessive weight. Limiting excessive adiposity in childhood and adolescence should help to avoid excessive loading and stresses on the lumbar spine.

Four-Year Gain in Bone Mineral in Girls With and Without Past Forearm Fractures: A DXA Study†

We have previously shown that girls with a recent distal forearm fracture have weaker skeletons than girls who have never fractured. This could be a transient or persistent phenomenon. The present study was undertaken to determine whether the bone mineral content (BMC) of girls with previous distal forearm fractures remains lower 4 years postfracture or if catch‐up gain has occurred. We report baseline and follow‐up dual energy X‐ray absorptiometry (DXA) results for 163 girls: 81 girls from the original control group who remained free of fracture (group 1) and 82 girls from the original group with distal forearm fractures (group 2). In data adjusted for bone area, height, weight, and pubertal status, group 2 girls had 3.5‐8.5% less BMC at the total body, lumbar spine, ultradistal radius, and hip trochanter than group 1 at baseline, and 2.4‐5.7% less BMC at these sites at follow‐up. Even girls from group 2 who did not experience another fracture after baseline (n = 58) did not display greater BMC at follow‐up compared with baseline values at any site, indicating that the decreased BMC at the time of fracture had persisted. In group 2, the relative gain in BMC after adjusting for the initial BMC and current bone area, height, weight, and pubertal stage was less than or similar to, but not greater than that of group 1 (ratio [95% CI]: total body, 0.985 [0.972‐0.998]; lumbar spine, 0.961 [0.935‐0.987]; ultradistal radius, 0.968 [0.939‐0.998]; hip trochanter, 0.955 [0.923‐0.988]; femoral neck, 0.981 [0.956‐1.007]; and 33% radius 0.999 [0.977‐1.021]). These findings indicate that girls with distal forearm fractures do not improve their gain of BMC. We conclude that girls who have sustained a distal forearm fracture maintain their lower BMC at most sites for at least 4 years.

Body composition of 4- and 5-year-old New Zealand girls: a DXA study of initial adiposity and subsequent 4-year fat change

BACKGROUND: Dual-energy X-ray information (DXA) quantitating body fat mass and percentage fat in healthy children of preschool age is scarce.OBJECTIVE: To study the initial variability in body composition and subsequent longitudinalchanges in absolute fat mass (kg) and relative adiposity (fat percentage) in a sample of contemporary young New Zealand girls.DESIGN: Cross-sectional study with a longitudinal component.SETTING: University research unit.SUBJECTS: A total of 89 Caucasian girls aged 4–5 y were recruited by advertisement at baseline and 4-y changes in body composition were evaluated in 23 of these girls.METHODS: Total body composition was measured by DXA, height and weight by anthropometry.RESULTS: Baseline values for fat mass varied more than values for lean mass or bone mass. Girls from the upper third of our fat percentage distribution (% fat >19.2%) had more than twice the fat mass (5.34 vs 2.31 kg, P<0.001) of those from the lowest third (% fat <15.4%). The percentage gain in fat mass over 4 y (124 (95% CI 90–163) also exceeded the percentage gain of lean mass (55 (95% CI 51–59). In data adjusted for age and height, 63.5% of the variance in percentage body fat at time 2 was explained by fat mass at time one.CONCLUSIONS: In girls, the trajectory of fat gain appears to be established at a young age. Our results support the view that body fatness tracks strongly before puberty. Since preventing the accumulation of excessive fat is preferable to reduction of existing excessive fat stores, it is important to put in place strategies to limit excessive fat gain early in life.