Examining bone surfaces across puberty: A 20-month pQCT trial

This follow-up study assessed sex differences in cortical bone growth at the tibial midshaft across puberty. In both sexes, periosteal apposition dominated over endosteal resorption. Boys had a greater magnitude of change at both surfaces, and thus, a greater increase in bone size across puberty. Relative increase in cortical bone area was similar between sexes

Accuracy and precision of internal displacement and strain measurements in long human bones using HR-pQCT and digital volume correlation

Digital volume correlation (DVC) is a technique for measuring 3D, internal displacements and strains in loaded structures. One application of DVC is the study of internal bone mechanics and the validation of subject-specific finite element (FE) models. While micro-computed tomography (µCT) is a common choice for DVC studies of small samples of bone, long human bones such as the tibia may exceed the spatial limitations of conventional µCT. High resolution peripheral quantitative CT (HR-pQCT) scanners, with their large bore and open-ended design, may be a viable option for long-bone DVC. However, HR-pQCT is afflicted by stitching artefacts, caused by the stacking of scan blocks to form the large scan volume, resulting in erroneous steps in DVC displacements and bands of increased strain error. This study proposed a modified HR-pQCT scanning protocol and stitching methodology to mitigate the effects of stitching artefacts on DVC measurements of displacement and strain. With the application of the proposed scanning/stitching methodology, displacements greater than 11.7µm (0.29 voxels) and strains greater than 1633µε could be repeatedly measured by DVC. These results show that HR-pQCT combined with DVC is suitable for measuring internal bone displacements in long human bones with sub-voxel precision and strains greater than 1633µε.</p

A longitudinal study of the relationship of physical activity to bone mineral accrual from adolescence to young adulthood

Physical activity in adolescence is beneficial for increasing bone mineral accrual; however, it's unclear whether these benefits persist into adulthood. This prospective study investigated whether physically active adolescents maintained their higher bone mineral content (BMC) into the third decade of life when compared to their less active peers. Data were from 154 subjects (82 females and 72 males) who participated in the University of Saskatchewan's Pediatric Bone Mineral Accrual Study (1991–1997), entry age 8 to 15 years. Participants returned for follow-up as young adults (2002–2006), follow-up age 23 to 30 years. Dual energy X-ray absorptiometry was used to measure BMC of total body (TB), lumbar spine (LS), total hip (TH) and femoral neck (FN) annually from 1991 to 1997 and from 2002 to 2006. Peak height velocity (PHV) was determined for each child as a measure of maturity. Age and gender-specific activity Z-scores were calculated for each participant based on the mean physical activity scores obtained from bi-annual questionnaire data during childhood and adolescence. Subjects were ranked into three adolescent activity groups: active, average and inactive (top, middle two, and bottom quartiles, respectively). Analysis of covariance (ANCOVA) was used to compare adjusted TB, LS, TH and FN BMC across the three adolescent activity groups at 1 year post PHV and in young adulthood. When compared to the inactive group, active males had 8% greater adjusted BMC at the TB, 13% at the LS and 11% at the TH (p 0.05). It was found that active adolescent males had 8–10% more adjusted BMC at the TB, TH and FN (p < 0.05) in young adulthood and that active adolescent females had 9% and 10% more adjusted BMC at the TH and FN. These results suggest that the skeletal benefits of physically activity in adolescents are maintained into young adulthood

Moderate to vigorous physical activity and impact loading independently predict variance in bone strength at the tibia but not at the radius in children

Objectives: To assess if daily minutes of moderate-to-vigorous physical activity (MVPA) or vigorous physical activity (VPA) and impact counts (acceleration peaks ≥3.9g) would independently predict variance in bone strength in children and youth. Second, to estimate bone strength gain associated with increases in daily MVPA, VPA or impact counts. Methods: We recorded 7-day activity of 49 participants, mean age 11.0; SD 1.7 years, using accelerometers and estimated radius and tibia bone strength using peripheral quantitative computed tomography. We used linear regression models adjusted for sex, body mass and muscle area to address objectives. Results: Daily MVPA (mean 50, SD 23 min) and VPA (17, 11) or impacts (71, 59 counts) did not predict variance in radius strength. Daily VPA (β=0.24), predicted variance in tibia strength at the distal and shaft sites, shaft strength was also predicted by MVPA (β=0.20) and impact counts (β=0.21). Our models estimated a 3-6%, 4%, and 4-11% gain in tibia strength after increasing daily MVPA by 10-20 min, VPA by 5 min, or impacts by 30-100 counts, respectively. Conclusions: Daily minutes MVPA, VPA and impact counts were independent predictors of tibia but not radius strength. Objective recording of activities associated with forearm bone strength and trials testing efficacy of increasing daily MVPA, VPA and related impacts on bone strength development in children and youth are warranted.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Does childhood and adolescence fracture influence bone mineral content in young adulthood?

Previous fracture may predispose an individual to bone fragility because of impaired bone mineral accrual. The primary objective of the study was to investigate the influence of fractures sustained during childhood and (or) adolescence on total body (TB), lumbar spine (LS), femoral neck (FN), and total hip (TH) bone mineral content (BMC) in young adulthood. It was hypothesized that there would be lower TB, LS, FN, and TH BMC in participants who had sustained a pediatric fracture. Participant anthropometrics, physical activity, and BMC (measured with dual energy X-ray absorptiometry) were assessed longitudinally during childhood and adolescence (from 1991 to 1997), and again in young adulthood (2002 to 2006). Sex, adult height, adult lean mass, adult physical activity, and adolescent BMC adjusted TB, LS, FN, and TH BMC in young adulthood, for those who reported 1 or more fractures (n = 42), were compared with those who reported no fractures (n = 101). There were no significant differences (p > 0.05) in adjusted BMC between fracture and nonfracture groups at the TB, LS, FN, and TH sites in young adulthood. These results suggest that fractures sustained during childhood and adolescence may not interfere with bone mass in young adulthood at clinically relevant bone sites

Maturity- and sex-related changes in tibial bone geometry, strength and bone–muscle strength indices during growth: A 20-month pQCT study

During growth, bone strength is conferred through subtle adaptations in bone mass and geometry in response to muscle forces. Few studies have examined the changes in bone geometry, strength and the bone–muscle strength relationship across maturity in boys and girls. Our aims were to describe (i) 20-month changes in bone geometry and strength at the tibial midshaft across three maturity groups of boys and girls, (ii) differences in these adaptations between sexes at the same approximate level of maturity and (iii) the bone–muscle strength relationship across maturity groups of boys and girls and between sexes. We used peripheral quantitative computed tomography (pQCT, Stratec XCT-2000) to measure change in total bone cross-sectional area (ToA, mm2), cortical area (CoA, mm2), average cortical thickness (C.Th., mm), section modulus (mm3) and muscle cross-sectional area (mm2) at the tibial midshaft (50% site) in 128 EARLY-, PERI- and POST-pubertal girls (n = 69, 11.9 ± 0.6 years) and boys (n = 59, 12.0 ± 0.6 years) across 20 months. We also calculated two bone–muscle strength indices (BMSI) for compression (CoA/MCSA) and bending [strength index/MCSA; where strength index = Z / (tibial length / 2)]. EARLY boys and girls had smaller ToA at baseline than same sex PERI or POST participants. There were no sex differences in ToA or CoA at baseline; however, boys increased both parameters significantly more than girls in every maturity group (8.5–11.1%, P < 0.01). These changes in bone geometry conferred greater gains in bone strength for boys compared with girls in each maturity group (13.8–15.6%, P < 0.01). Baseline BMSIs did not differ between sexes for EARLY and PERI groups, whereas BMSIs were significantly higher for POST boys compared with POST girls (P < 0.05). BMSIs decreased for EARLY and PERI girls (−7.4–(−1.1%)) whereas the ratios remained stable for EARLY and PERI boys (−0.6–2.5%). This sex difference in BMSI change was due to a relatively greater increase in CoA among EARLY and PERI boys compared with same-maturity girls. BMSIs remained stable in POST girls and decreased in POST boys due to relatively greater gains in MCSA. This study provides novel longitudinal descriptions of the maturity- and sex-specific changes in bone geometry, strength and bone–muscle strength indices