Transcript No Slide Title

Bone Health and
Assessment in Children
Virginia Stallings, MD
The Children’s Hospital of Philadelphia
University of Pennsylvania School of Medicine
Overview
 Assessing bone health in children:

Quantitative Ultrasound (QUS)

Dual Energy Xray Absorptometry (DXA)

Peripheral Quantitative Computed Tomography (pQCT)

DXA – Distal Femur site
 Body Composition
 Development of a Calcium Food Frequency Questionnaire
 Vitamin D status
Bone Health Assessment
Children
are not
little adults!
http://www.bowhouse.com.au
Ultrasound Sites and Techniques
Phalanges – IGEA
Tibia – Sunlight Omnisense
Calcaneus – Sahara, Cuba
From Baroncelli 2008, Pediatric
Research 62(3): 220-228.
Principles of QUS
 Properties of the ultrasound wave (shape,
amplitude) are altered by the material through
which it passes in a way that is characteristic
of the structural properties of the material
 Material density and biomechanical
properties (elastic modulus, compressive
strength) of bone influence QUS waves
Principles of QUS
 Trabecular bone
scatters energy of
ultrasound waves
 Cortical bone
absorbs energy of
ultrasound waves
Principles of QUS
 QUS applied to peripheral sites (calcaneus,
phalanges, patella, radius, tibia)
 Most ultrasound devices use a transmitter
and detector to measure attenuation of the
ultrasound wave
 Critical angle reflectometry uses a single
probe to measure the reflected wave as it
travels along cortical bone and determine the
speed of sound
Speed of Sound
SoS – speed of sound; AD-SoS – amplitude dependent SoS;
BTT – Bone transmission time (independent of soft tissue)
From Baroncelli 2008, Pediatric
Research 62(3): 220-228.
Sunlight Omnisense
 Portable
 Versatile – can
measure radius or tibia
 Probe sizes for different
ages/sizes
 Pediatric reference data
from Israel
QUS Pediatric Reference Data
Tibia
Radius
From Zadik et al. Osteoporosis International (10):857-62, 2003
Quantitative Ultrasound (QUS)
 Advantages:
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Rapid assessment
Radiation-free
Inexpensive and portable
Easily accessible measurement sites
Can be used in subjects without sleep/sedation
Limitations:
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What are the bone properties (cortical vs
trabecular) being measured?
Is it stable within an individual, and predictive of
fracture?
Dual energy x-ray absorptiometry - DXA
• Bone Mass, gm
• Bone area, cm2
• Bone Density, gm/cm2
Advantages of DXA
 Non-invasive test for measurement of BMD
 Rapid, safe, easily tolerated, very low
radiation exposure
 Can assess bone density at different skeletal
sites, both axial and peripheral
 Widely available (100,000 in operation)
 Excellent precision in children and adults
Pediatric Applications for DXA
 Hologic infant software - Whole Body Scan
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Requires no movement (sleep or sedation)
Clothing / swaddling material can affect body
composition results
No reference data for current generation of
DXA scanners
Pediatric Applications for DXA
 Infant Spine scans
 Not traditionally used for infants
 Rapid scan time
 Doesn’t require sedation
 No body composition data, but clothing less of an issue
Success Rate for Infant DXA Measurements
Cincinnati Children's Medical Center
All Study
Last 100
Age
Subjects
Subjects
6-12 mo
46/62 = 74% 25/31 = 81%
12-18 mo
26/35 = 74% 13/14 = 93%
18-24 mo
34/39 = 87% 25/26 = 96%
24-30 mo
34/36 = 94% 20/21 = 95%
30-36 mo
32/33 = 97% 15/16 = 94%
Why do both DXA and QUS
 Tibia QUS is a measure of cortical bone
 DXA spine scan is an integrated measure of
cortical and trabecular bone
 Studies of cortical and trabecular bone
density changes during puberty stage
suggest different effects in the 2 bone
compartments
Why do both DXA and QUS
 DXA can also be used for non-traditional
measurement sites like the tibia to validate
tibia QUS measurements
 DXA is widely available and used clinically for
children and adults, so study results may
have greater clinical utility
1,200
900
1,000
1,100
Cortical Density, gm/cm3
150
200
250
300
350
1,300
Puberty Effects on Tibia Trabecular and
Cortical Bone Density in Girls and Boys
FM
1
FM
FM
FM
FM
2
3
4
5
Breast / Genital Stage
FM
1
FM
FM
FM
FM
2
3
4
5
Breast / Genital Stage
Other Measurement Sites
Radius
Distal
Femur
Distal
Femur
Peripheral Quantitative Computed
Tomography
Peripheral Quantitative CT
Total Density
Total Area
Cortical Density
Cortical Area
Bone Strength
Bone Strength Index =
(Moment of Inertia x Density)
Cortical Density
Cortical Area
Trabecular Density
Trabecular Area
Peripheral Quantitative CT
Muscle Cross
Sectional Area
66%
Cortical vBMD,
dimensions and
strength
38%
3%
Trabecular &
Total vBMD
Distal Femur DXA Scan
 Indicated for:
Children with contractures
 Indwelling hardware that would
interfere with a spine or total
body scan
 Anomalies that would interfere
with scan analysis or
interpretation at standard sites
 Might be especially useful for
immobilized children who may be
at increased risk of femur
fractures
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Zemel et al J Clin Dens 2009 (in press)
Henderson et al AJR Am J Roentgenol ;178:439
Development of the Calcium Counts
Questionnaire
 Conducted by interview with the assistance of food
models and probing by interviewer
 Recall over the previous 4 weeks because of the high
intra-individual variability in calcium intake
 Quantitative FFQ based on serving size and
frequency of intake
 First generation questionnaire:
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Modified an existing calcium food-frequency
questionnaire to capture foods that children usually eat
based on recommendations of experienced pediatric
research dietitians
Zemel et al (in review)
Development of the Calcium Counts
Questionnaire
 Second generation questionnaire
 Reviewed results of several hundred first
generation questionnaires
 Dropped items that were never selected
 Reviewed the CSFII data for African
Americans and Caucasians children –
identified the top 50 sources of dietary calcium
and added them to the questionnaire
 Panel of pediatric research dietitians reviewed
several nutrient content sources and assigned
calcium values to items by consensus
Zemel et al (in review)
Validation of the Calcium Counts
Questionnaire
 Compared results of the CCFFQ to 7-d
weighed food diaries in 139 children 7 to 10
years of age
 Conducted a test-retest over a 1 month
interval to determine reproducibility
 Concurrent validity was moderate (r=0.61)
and test-rest reliability was high (r=0.74)
 CCFFQ, like most FFQs, overestimated
calcium intake compared to weighed food
record
Zemel et al (in review)
Radiation Exposure
Source
Natural Radiation Sources
Natural background radiation at sea level
Roundtrip transcontinental airplane flight
QCT
Peripheral QCT (Stratec 2000)
Spine QCT
DXA (Hologic QDR-4500)
Lumbar spine
Lateral spine
Whole body
Hand-wrist x-ray
Ultrasound
Effective Dose
Equivalent (Sv)
3,000 per year
60
< 0.01
30 – 100
3.8
1.4
2.6
1
0
Gender differences in body
composition
From Butte et al. 2000 Ped Research 47(5):578-85
Pea Pod
(Air Displacement Plethysmograph)
Pea Pod Infant Body Composition
 Uses air displacement to determine body
volume
 With an accurate weight and volume
measurement →body density
 If assume that fat tissue has a constant
density, → body composition derived from
body density → fat-free mass, fat mass and
percent body fat
Pea Pod Infant Body Composition
 Rapid assessment
 Safe, reliable, accurate, provides immediate
results
 Used up to measure infants up to ~4 to 6
months of age (1 to 8kg 1kg)
 Length is the usual limtation
SUMMARY
 Major advances in technology support bone
health assessment in all ages
 Optimal reference data are limited
 Interpretation of results are complex in
children with illness
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Stature, FFM, velocity
Not just age and gender