Update of the previous presentation of the topic of bone mineral densitometry in children. HAZ method (height for age Z-score) for height adjustment was introduced in this version.

1. BONE MINERAL
DENSITY IN CHILDREN
Ramin Sadeghi, MD
Associate Professor of Nuclear Medicine,
Mashhad University of Medical Sciences

2. Specific issues associated with bone
densitometry in children
• DXA BMD measurements are two-dimensional
• they represent a composite of bone size and bone density and are
highly related to body size.
• Children may have low bone mineral content (BMC) or aBMD
either because they have smaller bones, and/or because they have
less mineral than expected for the size of their bones (that is,
reduced bone density).
• There are several methods for adjustment for bone and/or
body size in order to avoid perhaps the most worrying
potential pitfall of diagnosing ‘low bone mass’ or
‘osteoporosis’ in a sick child who is merely very small for
his or her age.

3. Indicators for BMD scanning in children

4. Clinical situations in which bone densitometry
scanning is inappropriate in children

5. Systemic long term corticosteroids
• It is currently not possible to define the dosage and
duration of corticosteroid treatment which would warrant a
bone density scan in a child.
• It is also difficult to separate the impact of the
corticosteroids on bone from the effects on the skeleton of
the chronic inflammatory condition for which they are
being used for therapy.

6. Chronic Inflammatory disease
• Rheumatological conditions
• Juvenile idiopathic arthritis
• Systemic lupus erythematosis
• Dermatomyositis.
• Inflammatory bowel disease
• Particularly Crohn’s disease.
• Chronic liver disease, particularly cholestatic liver disease

7. Hypogonadism
• Primary hypogonadism e.g. ovarian or testicular failure
• Secondary to a failure to secrete gonadotrophins from the
pituitary gland.
• Hypopituitarism
• Galactosaemia in teenage girls
• Klinefelter’s Syndrome
• Thalassaemia Major.

8. Prolonged Immobilisation
• There are several examples of conditions in children that
can result in immobilisation such as severe cerebral palsy
and spinal cord injuries.

9. Osteogenesis Imperfecta
• As medical treatment with bisphosphonates has become
available in this condition in recent years, with evidence of
improved bone density and a reduction in fractures, it is
appropriate to perform a bone density scan, particularly
when treatment is being considered

10. Idiopathic Juvenile Osteoporosis
• It characteristically appears during early puberty with
evidence of back pain, difficulty walking and vertebral
compression fractures
• There are a number of documented reports of such
children being treated with bisphosphonates or active
vitamin D analogues

11. Recurrent low trauma fractures
• It is difficult to define precisely what constitutes a ‘low
trauma fracture’ other than one where the degree of force
involved appears inappropriate for the fracture.
• Children in this category may have a condition such as a
mild form of osteogenesis imperfecta

12. Apparent osteopenia on radiographs
• If osteopenia has been identified on radiographs, it is
worth documenting if there are any additional features
which may predict abnormal bone density such as
fractures, back pain, skeletal deformity or malnutrition
prior to a bone density scan.

13. Frequency of scans
• In clinical practice generally an interval of at least 18 to 24
months should be made between scans

14. Radiation Burden

16. Special considerations of BMD in children

17. Reference data
• The interpretation of DXA results relies upon the source of
reference data used
• Most often manufacturer specific data are used
• Other sources include locally derived data or that published in the
literature.
• The reference database used can significantly affect the
standard deviation scores (SDS) obtained from a scanner and
may therefore lead to misclassification of a child as osteopenic.
• While age, sex and ethnicity are known to affect BMD many of these
databases combine gender and ethnic groups
• were performed on previous releases of scanner models and software
• or include insufficient subjects.
• Interpreting results based on these databases may cause inaccuracies
when assessing an individual child’s bone status

20. Software
• The algorithms that separate bone from soft tissue have
been designed to optimise measurements in adults.
• Because of the changing body size and low mineralisation of the
bones, especially in smaller children, this may cause problems with
bone-edge detection and hence affect results.

22. Size dependence
• The most significant limitation of DXA is the size
dependence of the measurement.
• DXA provides a bone mineral density (BMD) based on a two-
dimensional projection of a three-dimensional structure. By doing
this, it does not account for the depth of the bone being measured.
The resultant BMD is called ‘areal’ BMD (aBMD) and is measured
in g/cm2.
• The net result of this is that the BMD of small bones is
underestimated and in large bones BMD is overestimated.
• In a growing child this will cause inaccuracies and it is
imperative that the size dependence of the technique is
accounted for when interpreting results.

24. How to perform DXA scans in children

25. Patient preparation
• Preparing a child for a DXA scan follows the same basic
principles as that for an adult. The operator will need to
record the child’s height and weight (in light indoor
clothes) and remove any metal objects which may cause
image artifacts, such as clothes with zips or buckles.
• To achieve optimum scan quality it is recommended that
the child is scanned in light indoor clothes or a hospital
gown.

26. Performing the scan
• Different age groups require different considerations and
particular attention is necessary when scanning children
with special needs.
• It is relevant to assess the child’s cooperation before
starting the scan to avoid any unnecessary radiation
exposure by having to repeat an unusable scan.

29. Official Pediatric Positions of the ISCD as
updated in 2013.

30. Fracture Prediction and Definition of
Osteoporosis
• The finding of one or more vertebral compression (crush)
fractures is indicative of osteoporosis, in the absence of local
disease or high-energy trauma. In such children and
adolescents, measuring BMD adds to the overall assessment of
bone health.
• The diagnosis of osteoporosis in children and adolescents
should not be made on the basis of densitometric criteria alone.
• In the absence of vertebral compression (crush) fractures, the
diagnosis of osteoporosis is indicated by the presence of both a
clinically significant fracture history and BMD Z-score ≤ -2.0.
• A clinically significant fracture history is one or more of the following:
• 1) two or more long bone fractures by age 10 years;
• 2) three or more long bone fractures at any age up to age 19 years.
• A BMC/BMD Z-score > -2.0 does not preclude the possibility of
skeletal fragility and increased fracture risk.

31. DXA Interpretation and Reporting in
Children and Adolescents
• DXA is the preferred method for assessing BMC and areal
BMD.
• The posterior-anterior (PA) spine and total body less head
(TBLH), are the preferred skeletal sites for performing BMC
and areal BMD measurements in most pediatric subjects.
• Other sites may be useful depending on the clinical need.
• The hip is not a preferred measurement site in growing children due to
variability in skeletal development.
• If a follow-up DXA scan is indicated, the minimum interval
between scans is 6-12 months.
• In children with short stature or growth delay, spine and TBLH
BMC and areal BMD results should be adjusted. For the spine,
adjust using either BMAD or the height z-score. For TBLH,
adjust using the height z-score..

34. Subtotal vs. Total

35. Terminology
• T-scores should not appear in pediatric DXA reports.
• The term “osteopenia” should not appear in pediatric DXA
reports.
• The term “osteoporosis” should not appear in
pediatric DXA reports without a clinically significant
fracture history.
• “Low bone mass or bone mineral density” is the preferred
term for pediatric DXA reports when BMC or areal BMD Z-
score are less than or equal to -2.0 SD.

36. Densitometry in Infants and Young
Children
• DXA is an appropriate method for clinical densitometry of infants and young
children.
• DXA lumbar spine measurements are feasible and can provide reproducible
measures of BMC and aBMD for infants and young children 0-5 years of
age.
• DXA whole body measurements are feasible and can provide reproducible
measures of BMC and aBMD for children ≥ 3 years of age.
• DXA whole body BMC measurements for children < 3 years of age are of
limited clinical utility due to feasibility and lack of normative data.
• Areal BMD should not be utilized routinely due to difficulty in appropriate positioning.
• Forearm and femur measurements are technically feasible in infants and
young children, but there is insufficient information regarding methodology,
reproducibility and reference data for these measurements sites to be
clinically useful at this time.
• In infants and children below 5 years of age, the impact of growth delay on
the interpretation of the DXA results should be considered, but it is not
quantifiable presently.

37. DXA Nomenclature
• DXA – not DEXA.
• T-score – not T score, t-score, or t score
• Z-score – not Z score, z-score, or z score

38. DXA Decimal Digits
• BMD:
• (example, 0.927 g/cm2) 3 digits
• T-score:
• (example, -2.3) 1 digit
• Z-score:
• (example, 1.7) 1 digit
• BMC:
• (example, 31.76 g) 2 digits
• Area:
• (example, 43.25 cm2) 2 digits
• % reference database:
• (example, 82%) Integer

39. Interpretation of bone mineral density
measured by DXA
• The T-score is completely meaningless in a growing
• child and must not be used for the interpretation of
aBMD in children
• The DXA manufacturer’s software packages usually
include paediatric aBMD reference databases which
enable an individual patient’s aBMD to be expressed as
SDS.
• However, such databases should be used with caution as Leonard
et al38 have shown that the use of different published paediatric
DXA reference databases for assessment of aBMD in children with
chronic diseases leads to significant inconsistencies in the
diagnosis of osteopenia, arbitrarily defined as an aBMD of less
than 2 SDS below the mean for age

40. What are the available databases in Iran
• Local database for Iranian population is very limited.
• The only available database is by Jeddi et al.
• Arch Osteoporos. 2013;8:114. doi: 10.1007/s11657-012-0114-z.
Epub 2013 Jan 8. Normative data and percentile curves of bone
mineral density in healthy Iranian children aged 9-18 years.
Jeddi et al
• Jeddi M, Bagheri Z, Dabbaghmanesh MH, Omrani GR,
Bakhshayeshkaram M. Revised reference curves of bone mineral
density according to age and sex for Iranian children and
adolescents. Arch Osteoporos. 2018;13(1):132. Published 2018
Nov 19. doi:10.1007/s11657-018-0546-1

43. Group work
• Use Jeddi et al database to provide Z-score for the
following total body BMD

46. Methods of correcting DXA results for
size
• Areal BMD is a function of a bone’s size and vBMD;
aBMD increases with bone size, due to the greater
thickness of larger bones.
• Thus, an increase in a child’s aBMD might reflect an
increase in bone size or vBMD, or a mixture of both. The
interpretation of aBMD poses major challenges in healthy
children, due to changes in bone size related to age and
puberty, and in children with chronic diseases in whom
poor growth and delayed puberty adversely affect bone
size.

47. HAZ: Height for age Z-score
• The most accurate method for height adjustment.
• In Iranian children can be done for Hologic device using
Jeddi et al database.
• The Z-score of height for age is calculated and then used for Z-
score adjustment

48. Jeddi et al Database for HAZ

49. Height or weight adjusted for age
• The least accurate method
• The height or weight of the patient is interpolated for the
appropriate age and a new Z-score for that age is
calculated.

53. Bone mineral apparent density (BMAD)
• One approach involves the calculation of bone mineral
apparent density (BMAD) by dividing BMC by the three-
dimensional bone volume derived from its two-
dimensional projected BA.
• The BMAD of the lumbar spine (LS) is estimated by
modelling it as a cube (BMADLS = BMCLS/BALS
1.5) or as
cylinder (BMADLS = BMCLS x [4/(π x bone width of LS)]).
• We still need a normal database for BMAD according to
age in order to be able to give a meaningful Z-Scores.

55. Bone mineral apparent density (BMAD)
• The only available Iranian database for BMAD in children
is by Jeddi et al.
• They used the following formulae

58. Molgaard method
• Mølgaard et al have proposed a three-step approach for
the evaluation of whole body BMC in children, which seek
to determine the following:
• (1) Is the child’s height appropriate for age? (‘short bones’);
• (2) Is the bone size (bone area) appropriate for height? (‘narrow
bones’);
• (3) Is the BMC appropriate for bone area? (‘light bones’).
• Once these analyses have been performed they are used to
calculate SDS by reference to local gender and ethnic specific
reference data for these parameters.

59. Molgaard method
• The only available database for Molgaard method in Iran
is Jeddi et al again.

62. Clinical examples
• Norland devices
• The main database is Zanchetta
• It has database for 2-20 y/o
• It has database for lumbar spine, femoral neck, total body, and
forearm.
• For lumbar spine the database uses L2-L4 for measurements
• Height adjustment can only be done by height adjustment for age
• No Iranian database is available

63. A 5 y/o male patient with OI

65. Clinical examples
• Hologic devices
• The device own database gives Z-values for
• Lumbar spine 3 y/o onward
• Femoral neck 5 y/o onward
• Total body less head 8 y/o onward

67. 9 y/o onward Hologic devices
• There is an Iranian database available (Jeddi et al) for
lumbar spine, femoral neck, and total body less head.
• It also provides normal values for BMAD and Molgaard method
(BMC of total body for body area)

68. A 16 y/o male patient with OI

69. Same patient femoral neck

70. Same patient total body

71. Same patient HAZ method

72. A 16 y/o male patient with lipopolysacaridosis
Height: 135 cm

73. The same patient femoral neck

74. The same patient lumbar spine

75. Adjustment for Tanner stage
• There is a very important database for Hologic devices
which provide adjustment for weight and Tanner stage
• Southard et al. Bone Mass in Healthy Children: Measurement with Quantitative DXA
• Can be used for 3 y/o onward
• We use this database for 3-9 y/o patient to generate Z-
Score

76. A 14 y/o female patient with growth
retardation and OI, Tanner stage II

77. A 4 y/o female patient with OI

78. The same patient
• Femoral neck area
processing is not
possible!

79. A 1 y/o male patient with OI
• No database is
available for whole
body measurement

80. The same patient lumbar spine
• Salle et al. Acta Paediatr
81: 953-8. 1992 database
should be used.
• A block of L1-L5 in whole
should be measured
• The exact age in months
is needed.

82. Follow up
• BMD in children is highly age dependent.
• Any significant decreased in Z-score should be
considered important even if in the normal range.
• Even increase in BMD in the presence of decreased Z-score
denotes to a deterioration.

84. A patient with OI: baseline and follow up

85. Another patient with OI with a follow up
scan

86. Same patient after two years

87. Follow up
Despite 3.2%
increase in
BMD, Z-score
decreased
denoting to a
deterioration

88. VFA
• Vertebral Fracture Assessment (VFA) is a useful method
for evaluation of lumbar spine fractures.
• Can be done with ease and takes only couple of seconds
with minimal exposure

89. A 18 y/o male patient with history of long
term corticosteroid therapy

90. A 16 y/o male patient with adrenal
insufficiency and steroid therapy

91. Metal device problem
• If possible the limbs without metal device should be used
and copied to the side with metal device

92. A 16 y/o female patient with