Melonie Burrows

University of British Columbia - Vancouver, Vancouver, British Columbia, Canada

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Publications (14)42.01 Total impact

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    ABSTRACT: People with neurofibromatosis 1 (NF1) have low bone mineralization, but the natural history and pathogenesis are poorly understood. We performed a sibling-matched case-control study of bone mineral status, morphology, and metabolism. Eighteen children with NF1 without focal bony lesions were compared to unaffected siblings and local population controls. Bone mineral content at the lumbar spine and proximal femur (dual energy X-ray absorptiometry (DXA)) was lower in children with NF1; this difference persisted after adjusting for height and weight. Peripheral quantitative computed tomography (pQCT) of the distal tibia showed that trabecular density was more severely compromised than cortical. Peripheral QCT-derived estimates of bone strength and resistance to bending and stress were poorer among children with NF1 although there was no difference in fracture frequencies. There were no differences in the size or shape of bones after adjusting for height. Differences in markers of bone turnover between cases and controls were in the directions predicted by animal studies, but did not reach statistical significance. Average serum calcium concentration was higher (although within the normal range) in children with NF1; serum 25-OH vitamin D, and PTH levels did not differ significantly between cases and controls. Children with NF1 were less mature (assessed by pubertal stage) than unaffected siblings or population controls. Children with NF1 have a generalized difference of bone metabolism that predominantly affects trabecular bone. Effects of decreased neurofibromin on bone turnover, calcium homeostasis, and pubertal development may contribute to the differences in bone mineral content observed among people with NF1. © 2013 Wiley Periodicals, Inc.
    American Journal of Medical Genetics Part A 05/2013; · 2.30 Impact Factor
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    ABSTRACT: Physical activity (PA) has positive effects on bone accrual and geometry in children during growth. However, we do not know how PA influences adaptations in bone architecture during growth. We evaluated the contribution of PA to bone density, architecture and strength in adolescents. We used HR-pQCT (XtremeCT, Scanco Medical) to assess cross-sectional moments of inertia [Imin, Imax (mm⁴)], total bone density (Tt.Dn, mg HA/cm³), total bone area (Tt.Ar, mm²), cortical bone density (Ct.Dn, mg HA/cm³), cortical thickness (Ct.Th, μm), trabecular bone density (Tb.Dn, mg HA/cm³), trabecular number (Tb.N, mm⁻¹) and trabecular thickness (Tb.Th, μm) at the distal tibia in 146 male and 132 female participants (15-20 years). We evaluated the contribution of impact loading PA (ImpactPA) and non-impact loading PA (NoimpactPA) on bone (p < 0.05). ImpactPA explained 10% of variance in Imin (p = 0.000), and 12% of variance in Imax (p = 0.000) in male participants. In male participants, ImpactPA explained 6% of variance in Tt.Ar (p = 0.003). In female participants, ImpactPA explained 4% of variance in Tt.Dn (p = 0.011), 5% of variance in Tb.Dn (p = 0.004) and 8% of variance in Tb.N (p = 0.001). Our findings suggest that ImpactPA is significantly associated with bone architecture and bone strength in adolescent males and females.
    Acta Paediatrica 01/2011; 100(1):97-101. · 1.97 Impact Factor
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    ABSTRACT: High-resolution quantitative computerized tomography permits evaluation of site specific differences in bone architecture. The purpose of this study was to compare bone architecture between distal radius and distal tibia. We present bone architecture at the distal radius and distal tibia in 151 male and 172 female participants, as follows: total bone area (mm(2)), total bone density (mg HA/cm(3)), trabecular bone density (mg HA/cm(3)), cortical bone density (mg HA/cm(3)), cortical thickness (μm), trabecular number (1/mm), trabecular thickness (μm), and trabecular separation (μm). We evaluated differences in and correlations between bone variables (absolute values) across sites. We calculated individual z scores and used regression to assess discordance between sites. In pubertal and postpubertal male and female participants, absolute values of total bone area, cortical bone density, cortical thickness, and trabecular thickness were significantly lower at the radius compared with the tibia (P < 0.01). Absolute values for trabecular bone density were significantly lower at the radius compared with the tibia in postpubertal male and female participants (P < 0.01). Absolute values for trabecular separation was significantly lower at the radius compared with the tibia in pubertal female participants (P < 0.01). Bone architecture was moderately to highly correlated between sites (r = 0.34-0.85). There was discordance between z scores at the radius and tibia within male participants (pubertal R (2) between 36 and 64%; postpubertal R (2) between 22 and 77%) and female participants (pubertal R (2) between 10 and 44%; postpubertal R (2) between 25 and 62%). In conclusion, it is vital to evaluate bone architecture at the specific skeletal site of interest.
    Calcified Tissue International 10/2010; 87(4):314-23. · 2.75 Impact Factor
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    ABSTRACT: We examined the use of high-resolution peripheral quantitative computed tomography (HR-pQCT [XtremeCT; Scanco Medical, Switzerland]) to assess bone microstructure at the distal radius in growing children and adolescents. We examined forearm radiographs from 37 children (age 8-14 yr) to locate the position of the ulnar and radial growth plates. We used HR-pQCT to assess bone microstructure in a region of interest (ROI) at the distal radius that excluded the growth plate (as determined from the radiographs) in all children (n=328; 9-21 yr old). From radiographs, we determined that a ROI in the distal radius at 7% of bone length excluded the radial growth plate in 100% of participants. We present bone microstructure data at the distal radius in children and adolescents. From the HR-pQCT scans, we observed active growth plates in 80 males (aged 9.5-20.7 yr) and 92 females (aged 9.5-20.2 yr). The ulnar plate was visible in 9 male and 17 female participants (aged 11.2 ± 1.9yr). The HR-pQCT scan required 3 min with a relatively low radiation dose (<3 μSv). Images from the radial ROI were free of artifacts and outlined cortical and trabecular bone microstructure. There is currently no standard method for these measures; therefore, these findings provide insight for investigators using HR-pQCT for studies of growing children.
    Journal of Clinical Densitometry 01/2010; 13(4):451-5. · 1.71 Impact Factor
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    ABSTRACT: To render a diagnosis pediatricians rely upon reference standards for bone mineral density or bone mineral content, which are based on cross-sectional data from a relatively small sample of children. These standards are unable to adequately represent growth in a diverse pediatric population. Thus, the goal of this study was to develop sex and site-specific standards for BMC using longitudinal data collected from four international sites in Canada and the United States. Data from four studies were combined; Saskatchewan Paediatric Bone Mineral Accrual Study (n=251), UBC Healthy Bones Study (n=382); Penn State Young Women's Health Study (n=112) and Stanford's Bone Mineral Accretion study (n=423). Males and females (8 to 25 years) were measured for whole body (WB), total proximal femur (PF), femoral neck (FN) and lumbar spine (LS) BMC (g). Data were analyzed using random effects models. Bland-Altman was used to investigate agreement between predicted and actual data. Age, height, weight and ethnicity independently predicted BMC accrual across sites (P<0.05). Compared to White males, Asian males had 31.8 (6.8) g less WB BMC accrual; Hispanic 75.4 (28.2) g less BMC accrual; Blacks 82.8 (26.3) g more BMC accrual with confounders of age, height and weight controlled. We report similar findings for the PF and FN. Models for females for all sites were similar with age, height and weight as independent significant predictors of BMC accrual (P<0.05). We provide a tool to calculate a child's BMC Z-score, accounting for age, size, sex and ethnicity. In conclusion, when interpreting BMC in pediatrics we recommend standards that are sex, age, size and ethnic specific.
    Bone 10/2009; 46(1):208-16. · 4.46 Impact Factor
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    Melonie Burrows, Danmei Liu, Sarah Moore, Heather McKay
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    ABSTRACT: Bone is a complex structure with many levels of organization. Advanced imaging tools such as high-resolution (HR) peripheral quantitative computed tomography (pQCT) provide the opportunity to investigate how components of bone microstructure differ between the sexes and across developmental periods. The aim of this study was to quantify the age- and sex-related differences in bone microstructure and bone strength in adolescent males and females. We used HR-pQCT (XtremeCT, Scanco Medical, Geneva, Switzerland) to assess total bone area (ToA), total bone density (ToD), trabecular bone density (TrD), cortical bone density (CoD), cortical thickness (Cort.Th), trabecular bone volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular spacing standard deviation (Tb.Sp SD), and bone strength index (BSI, mg2/mm4) at the distal tibia in 133 females and 146 males (15 to 20 years of age). We used a general linear model to determine differences by age- and sex-group and age x sex interactions (p<0.05). Across age categories, ToD, CoD, Cort.Th, and BSI were significantly lower at 15 and 16 years compared with 17 to 18 and 19 to 20 years in males and females. There were no differences in ToA, TrD, and BV/TV across age for either sex. Between sexes, males had significantly greater ToA, TrD, Cort.Th, BV/TV, Tb.N, and BSI compared with females; CoD and Tb.Sp SD were significantly greater for females in every age category. Males' larger and denser bones confer a bone-strength advantage from a young age compared with females. These structural differences could represent bones that are less able to withstand loads in compression in females.
    Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research 10/2009; 25(6):1423-32. · 6.04 Impact Factor
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    ABSTRACT: We investigated the contribution of ethnicity, physical activity, body composition, and calcium intake to bone accrual across 7 years of growth. We assessed 80 Caucasian and 74 Asian boys and 81 Caucasian and 64 Asian girls at baseline and retained 155 children across all 7 years. Ethnicity, physical activity, and calcium intake were assessed by questionnaire; fat mass, lean mass, and bone mineral content (BMC) of the whole body (WB), lumbar spine (LS), total proximal femur (PF(TOT)), and femoral neck (FN) were measured using DXA (Hologic QDR 4500). We aligned children on peak height velocity and utilized multilevel modeling to assess bone mineral accrual. Height and lean mass accounted for 51.8% and 44.1% of BMC accrual in children. There was a significant difference in physical activity, calcium intake, and lean mass between Asians and Caucasian boys and girls at baseline and conclusion (p < 0.05). In boys, physical activity and ethnicity significantly predicted BMC accrual at the FN. In girls, Asians had significantly lower PF(TOT) and FN BMC. Calcium was a significant predictor of WB BMC accrual in boys and girls. In conclusion, our findings highlight the importance of accounting for ethnicity in pediatric studies. Physical activity, dietary calcium, and lean mass positively influence bone accrual and are lower in Asian compared to Caucasian children from a very young age.
    Calcified Tissue International 04/2009; 84(5):366-78. · 2.75 Impact Factor
  • M Burrows, D Liu, H McKay
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    ABSTRACT: We examined the feasibility of high-resolution peripheral quantitative computed tomography (HR-pQCT) to assess bone microstructure in adolescents. Low radiation doses and clear images were produced using a region of interest (ROI) at 8% of tibial length. Active growth plates were observed in 33 participants. HR-pQCT safely assessed important elements of bone microstructure in adolescents. We examined the feasibility and safety of HR-pQCT to assess tibial bone microstructure in adolescents. We used XtremeCT (Scanco Medical) to assess bone microstructure at the distal tibia in 278 participants (15-20 years old). The 2.8-min scan resulted in a relatively low radiation dose (<3 microSv) while producing artifact clear images in all participants. An 8% scan site was equivalent to 33 +/- 2 mm of total tibial length (400 +/- 30 mm). We observed active growth plates in 33 participants. The growth plate was located at 13 +/- 2 mm of total tibial length and was not included in the ROI for any participant. HR-pQCT safely assessed important elements of bone microstructure in adolescents. Given the important contribution of bone geometry and structure to bone strength, it is essential to better understand the development and adaptation of these parameters in cortical and trabecular bone compartments.
    Osteoporosis International 04/2009; 21(3):515-20. · 4.04 Impact Factor
  • Bone 01/2009; 44. · 4.46 Impact Factor
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    ABSTRACT: Peripheral quantitative computed tomography is a valuable tool to assess bone in children across growth, with long-term studies capturing nuances missed in cross-sectional studies. As children grow, a change from XCT 2000 to a XCT 3000 may be required to accommodate the increasing size of the lower limbs. We examined the precision and agreement between the Stratec XCT 2000 and 3000 on selected bone and muscle parameters. Twenty-eight participants (mean+/-SD; age 27.5+/-6.5 yr) underwent scans at the distal (8%), mid (50%), and proximal (66%) tibia sites, to assess total bone area, total bone density, and trabecular density (8% site); and total bone area, cortical area, cortical density (CoD), polar strength-strain index, and muscle cross-sectional area (50% and 66% sites). Outcomes between instruments were highly correlated; r=0.90-0.99 for CoD across sites, with r=0.97-0.99 for all other measures. Bland and Altman plots showed excellent agreement between instruments for all variables. Regression indicated no significant relationship between instrument and size of measurement (p>0.05). Coefficients of variation were lower than previously reported (0.4-2.4%). For longitudinal studies, the XCT 3000 can replace the XCT 2000 with minimal influence on bone and muscle parameters.
    Journal of Clinical Densitometry 11/2008; 12(2):186-94. · 1.71 Impact Factor
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    Karen Hind, Melonie Burrows
    Bone 06/2007; 41(5):906-907. · 4.46 Impact Factor
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    K Hind, M Burrows
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    ABSTRACT: Osteoporosis is a serious skeletal disease and as there is currently no cure, there is a large emphasis on its prevention, including the optimisation of peak bone mass. There is increasing evidence that regular weight-bearing exercise is an effective strategy for enhancing bone status during growth. This systematic review evaluates randomised and non-randomised controlled trials to date, on the effects of exercise on bone mineral accrual in children and adolescents. An online search of Medline and the Cochrane database enabled the identification of studies. Those that met the inclusion criteria were included in the review and graded according to risk for bias. Twenty-two trials were reviewed. Nine were conducted in prepubertal children (Tanner I), 8 in early pubertal (Tanner II-III) and 5 in pubertal (Tanner IV-V). Sample sizes ranged from n=10 to 65 per group. Exercise interventions included games, dance, resistance training and jumping exercises, ranging in duration from 3 to 48 months. Approximately half of the trials (n=10) included ground reaction force (GRF) data (2 to 9 times body weight). All trials in early pubertal children, 6 in pre pubertal and 2 in pubertal children, reported positive effects of exercise on bone (P<0.05). Mean increases in bone parameters over 6 months were 0.9-4.9% in prepubertal, 1.1-5.5% in early pubertal and 0.3-1.9% in pubertal exercisers compared to controls (P<0.05). Although weight-bearing exercise appears to enhance bone mineral accrual in children, particularly during early puberty; it remains unclear as to what constitutes the optimal exercise programme. Many studies to date have a high risk for bias and only a few have a low risk. Major limitations concerned selection procedures, compliance rates and control of variables. More well designed and controlled investigations are needed. Furthermore, the specific exercise intervention that will provide the optimal stimulus for peak bone mineral accretion is unclear. Future quantitative, dose-response studies using larger sample sizes and interventions that vary in GRF and frequency may characterise the most and least effective exercise programmes for bone mineral accrual in this population. In addition, the measurement of bone quality parameters and volumetric BMD would provide a greater insight into the mechanisms implicated in the adaptation of bone to exercise.
    Bone 02/2007; 40(1):14-27. · 4.46 Impact Factor
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    Melonie Burrows
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    ABSTRACT: Osteoporosis is a serious skeletal disease causing an increase in morbidity and mortality through its association with age-related fractures. Although most effort in fracture prevention has been directed at retarding the rate of age-related bone loss and reducing the frequency and severity of trauma among elderly people, evidence is growing that peak bone mass is an important contributor to bone strength during later life. Indeed, there has been a large emphasis on the prevention of osteoporosis through the optimization of peak bone mass during childhood and adolescence. The prepubertal human skeleton is sensitive to the mechanical stimulation elicited by exercise and there is increasing evidence that regular weight-bearing exercise is an effective strategy for enhancing bone mineral throughout growth. Physical activity or participation in sports needs to start at prepubertal ages and be maintained through pubertal development to obtain the maximal peak bone mass achievable. High strain eliciting sports like gymnastics, or participation in sports or weight bearing physical activity like soccer, are strongly recommended to increase peak bone mass. Many other factors also influence the accumulation of bone mineral during childhood and adolescence, including heredity, gender, diet and endocrine status. However, this review article will focus solely on the effects of physical activity and exercise providing a summary of current knowledge on the interplay between activity, exercise and bone mass development during growth. Due to the selection bias and other confounding factors inherent in cross-sectional studies, longitudinal and intervention studies only will be reviewed for they provide a greater opportunity to examine the influence of mechanical loading on bone mineral accretion over time. Key pointsPre-pubertal children's ability to thermoregulate when exposed to hot and humid environments is deficient compared to adults.Research into the severity of heat-related illness in pre-pubertal children is inconclusive.Discretion should be used in applying findings from indoor studies to outdoor activities due to the influence of the velocity of circulating air on thermoregulation.
    Journal of sports science & medicine 01/2007; 6(3):305-312. · 0.89 Impact Factor
  • Osteoporos Int. 21(Suppl1):S45-S46.

Publication Stats

264 Citations
42.01 Total Impact Points

Institutions

  • 2007–2011
    • University of British Columbia - Vancouver
      • • Department of Orthopaedics
      • • Faculty of Medicine
      Vancouver, British Columbia, Canada
    • University of Leeds
      Leeds, England, United Kingdom
    • University of Exeter
      • Department of Sport and Health Sciences
      Exeter, England, United Kingdom
  • 2009
    • Centre for Hip Health and Mobility
      Vancouver, British Columbia, Canada
    • Vancouver Coastal Health
      Vancouver, British Columbia, Canada
    • University of Saskatchewan
      • College of Kinesiology
      Saskatoon, Saskatchewan, Canada