Weight-bearing physical activity has beneficial effects on bone health across the age spectrum. Physical activities that generate relatively highintensity loading forces, such as plyometrics, gymnastics, and high-intensity resistance training, augment bone mineral accrual in children and adolescents. Further, there is some evidence that exercise-induced gains in bone mass in children are maintained into adulthood, suggesting that physical activity habits during childhood may have long-lasting benefits on bone health. It is not yet possible to describe in detail an exercise program for children and adolescents that will optimize peak bone mass, because quantitative dose-response studies are lacking. However, evidence from multiple small randomized, controlled trials suggests that the following exercise prescription will augment bone mineral accrual in children and adolescents:

Physical Activity and Bone Health

Epidemiology of hip fractures

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(12)61263-X.pdf

Video capture of the circumstances of falls in elderly people residing in long-term care: an observational study

ContextOsteoporosis causes substantial morbidity and costs $13.8
billion annually in the United States. Measurement of bone mass by densitometry
is a primary part of diagnosing osteoporosis and deciding a preventive
treatment course. Bone mineral densitometry has become more widely available
and commonly used in practice.ObjectiveTo review evidence about the value of various clinical applications of bone densitometry.Data SourcesA MEDLINE search was performed to update previous meta-analyses of
the relationship between various measurements of bone density and risk of
vertebral and hip fracture. We used data from the prospective Study of
Osteoporotic Fractures to estimate risk of fracture from bone density and age
in postmenopausal women.Study Selection and Data ExtractionWhen available, meta-analyses and systematic reviews are emphasized in the review.Data SynthesisBone mineral density (BMD) predicts fracture and can be
used in combination with age to estimate absolute risk of fractures in
postmenopausal white women. Hip BMD predicts hip fracture more strongly than
other measurements of BMD. There are insufficient data to translate BMD results
into risk of fracture for men and nonwhite women. The benefits of treatments to
prevent fractures depend on BMD: women with osteoporosis have a greater risk of
fractures and greater benefit from treatments than women without osteoporosis.ConclusionsGuidelines based on systematic reviews and a
cost-effectiveness analysis have suggested that it is worthwhile to measure BMD
in white women older than 65 years and perhaps to use risk factors to select
younger postmenopausal women for densitometry. Other potential clinical
applications of BMD that have not yet been adequately studied include screening
men or nonwhite women, monitoring BMD in patients receiving treatment, and
using BMD to identify patients who should be evaluated for secondary causes of
osteoporosis.

https://jamanetwork.com/journals/jama/articlepdf/195421/JSR20013.pdf

Clinical use of bone densitometry: scientific review.

OSTEOPOROSIS IS IMPORtant because it is common and often occult, yet it causes substantial morbidity and costs $13.8 billion a year (1995 dollars) in the United States alone. Hip fractures account for most of the costs and deaths due to osteoporosis, but vertebral fractures also cause substantial pain and disability, and only about a third of these fractures are recognized clinically. Osteoporosis is defined by low bone mass and increased fragility of bone that increases the risk of fracture. Measurement of bone mass by densitometry has become central to the diagnosis of osteoporosis and decisions about treatment to prevent fracture.

Clinical Use of Bone DensitometryScientific Review

Etiology and prevention of age-related hip fractures.

To assess age-related changes in femoral strength as a component in the risk of fracture of the hip, we compared the loads at fracture of the proximal aspects of femora from the cadavera of older and younger individuals, as tested in a fall-loading configuration. To provide a basis for non-invasive in vivo estimates of femoral strength, we also determined the correlations between variables measured with dual-energy x-ray absorptiometry and these loads. Femora from the cadavera of eight older individuals (mean age, seventy-four years) and nine younger individuals (mean age, thirty-three years) were scanned with a Hologic QDR-2000 densitometer to obtain densitometric and geometric information. The femora were then tested mechanically in a loading configuration that simulated a fall on the greater trochanter. The femora from the older group were half as strong as those from the younger group (p < 0.001), and they absorbed one-third as much energy (p < 0.001). The area bone-mineral density of the femoral neck correlated strongly with the load at fracture (r2 = 0.92). CLINICAL RELEVANCE: The prevalence of fracture of the hip increases exponentially with age. 90 percent of those fractures are the result of a simple fall from a standing height.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related reductions in the strength of the femur tested in a fall-loading configuration

Results from previous quasi-static mechanical tests indicate that femurs from elderly subjects fail in vitro at forces 50% below those available in a fall from standing height However, bone is a rate-dependent material, and it is not known whether this imbalance is present at rates of loading which occur in a fall Based on recent data on time to peak force and body positions at impact during simulated falls, we designed a high rate test of the femur in a loading configuration meant to represent a fall on the hip We used elderly (mean age 735±74 (SD) years) and younger adult (327±128 years) cadaveric femurs to investigate whether (1) the strength, stiffness, and energy absorption capacity of the femur increases under high rate loading conditions; (2) elderly femurs have reduced strength, stiffness, and energy absorption capacity compared with younger adult femurs at this loading rate; and (3) densitometric and geometric measures taken at the hip correlate with the measured fracture loads Femurs were scanned using dual-energy X-ray absorptiometry (DXA) and then tested to failure in a fall loading configuration at a displacement rate of 100 mm/second The fracture load in elderly and younger adult femurs increased by about 20% with a 50-fold increase in displacement rate However, energy absorption did not increase with displacement rate because of a twofold increase in stiffness at the higher loading rate Age-related differences in strength and energy absorption capacity were consistent with those found previously for a displacement rate of 2 mm/second There were moderate to strong correlations between fracture load and DXA variables, with the best correlation provided by cross-sectional area (r2=077) and bone mineral density (BMD) (r2=072) at the femoral neck Our results indicate that, even at rates of loading applied during a fall, the estimated impact force in a fall on the hip is 35% greater than the average fracture load of the elderly femur Moreover, the relationship we found between femoral neck BMD and fracture load indicates that an increase in femoral neck BMD of more than 20% would be required to raise the strength of the femur to the level of the impact load As clinical trials of pharmacologic interventions have demonstrated increases in BMD of only a few percent at best, our results emphasize the continuing need for intervention strategies that focus on fall prevention and on reducing the severity of those falls that do occur

Effects of loading rate on strength of the proximal femur.

We assessed the bone mineral density (BMD) of 16 matched sets of cadaveric proximal femurs and feet using dual-energy x-ray absorptiometry (DXA). We also estimated the femoral neck length from the DXA scans. Quantitative ultrasound densitometry was used to measure the velocity of sound and broadband ultrasound attenuation (BUA) in the calcaneus of each foot. The proximal femurs were then tested to failure in a loading configuration designed to simulate a fall with impact to the greater trochanter. Femoral neck BMD and trochanteric BMD were strongly associated with the femoral failure load (r2=0.79 and 0.81, respectively; P<0.001), whereas femoral neck length was modestly correlated with femoral failure load (r2=0.27, P=0.04). Calcaneal BMD (r2=0.63, P<0.001) and BUA (r2=0.51, P=0.002) were also significantly associated with femoral failure load. Given the small sample size, we were unable to detect differences in the strength of the correlations between the independent parameters and femoral failure load. Using linear multiple regression analyses, the strongest predictor of femoral failure load was a combination of femoral neck BMD and femoral neck length (R2=0.85, P<0.001). Thus, it appears that both femoral and calcaneal bone mineral properties may be useful for identifying those persons at greatest risk for hip fracture.

Amy Courtney

Papers

Etiology and prevention of age-related hip fractures.

Age-related reductions in the strength of the femur tested in a fall-loading configuration

Effects of loading rate on strength of the proximal femur.

Ultrasound and densitometry of the calcaneus correlate with the failure loads of cadaveric femurs.

A thoracic mechanism of mild traumatic brain injury due to blast pressure waves.