1. Interpretation of DEXA
Bone Densitometry
Interpretation of DEXA

2. in the absence of other recognizable causes of bone loss.
Osteoporosis
Osteoporosis is the most common metabolic bone disorder. It has been defined by the National Institutes of Health as an age-related disorder characterized by decreased bone mass and increased susceptibility to fractures
in the absence of other recognizable causes of bone loss.

3. Osteoporosis
Type 1. involutional osteoporosis affects mainly trabecular bone, occurs in women during the years after the menopause, and is related to a lack of estrogen. This is thought to account for wrist and vertebral crush fractures, which occur through areas of principally trabecular bone.
Type 2. senile involutional osteoporosis. The fractures of old age seen at the hip, proximal humerus, pelvis and asymptomatic vertebral wedge fractures. This affects both trabecular and cortical bone and represents progressive loss of bone mass from the peak around the age of years.
Secondary osteoporosis is due to an underlying medical condition, such as renal disease, malabsorption, or hormonal imbalance, or to medical treatment such as steroids or certain anticonvulsants

4. Osteoporosis Risk factors
may be superimposed upon either involutional or secondary osteoporosis, including
smoking, alcohol, poor diet, lack of exercise, an early menopause, strong family history and small frame.

5. Osteoporosis
The normal rate of bone loss is 2% per year, hence 20-40% of the female bone mass is already lost by the age of 65 years of age, beginning before the menopause and accelerating afterwards

6. Osteoporosis
Bone mass is the major determinant of bone strength that can be measured by non-invasive techniques, and accounts for 75-85% of this parameter

7. Osteoporosis
Bone densitometry is clinically indicated for the detection and assessment of osteoporosis and for the evaluation and monitoring of several diseases and therapies. These include:
The detection of osteoporosis and assessment of its severity.
Evaluation of perimenopausal women for the initiation of estrogen therapy.
Evaluation of patients with metabolic diseases that affect the skeleton.
Monitoring of treatment and evaluation of disease course.
In addition it may be useful as an epidemiological tool and possibly in the future for screening
American Society of Bone and Mineral Research

8. Osteoporosis Measurement
Plain film, Subjective, Radiogrammetry, Osteogram
SPA
DPA
DEXA
QCT US
MRI

9. DEXA
Because photons of different energy are differentially attenuated by bone and soft-tissues, by measuring the percentage of each transmitted beam and then applying simple simultaneous equations, the absorption by bone alone and hence bone density can be calculated.
This measurement is not a true density but rather an areal density, represented in gms/cm2

10. DEXA y x

11. DEXA
DEXA has very high
accuracy (the difference in the measurement from a known standard) and
precision (observed deviation of serial measurements with time),
both short and long term, to within 1% at the hip and spine

12. DEXA DXA is at present the most precise measurement of BMD
QCT is more sensitive to change

13. DEXA
Interpretation

14. Find out as much
relevant information
as possible

15. Find out as much
relevant information
as possible

16. Bone Densitometry DEXA spine check list
Note the age, sex, ethnicity and weight
Does this match the reference ranges?
Is the bottom of L4 roughly at the level of the iliac crests
Are there any ribs on L1
Scoliosis
Are the vertebrae correctly divided
Anything in the soft tissue

18. Vertebroplasty

20. Calcium
Tablets

21. Wrong levels
Transitional vertebrae

22. Bone Densitometry DEXA spine check list
Look for significant level to level variations
15-20% difference between adjacent levels

23. DEXA, what makes a good scan?
5-15 Lines of Iliac Crest. I recommend 1/2 of L5.
5-10 Lines of T12.
2 cm of tissue on both sides of the spine.
Spine should be straight.
No metal in spine.

24. Common problems with spine scans.
Spine isn’t straight.
Scan starts in sacrum.
Scan stops too soon.
Wrong scan mode.
Scan doesn’t include L5.

25. What is a scan mode?
This determines the speed the arm travels, and how much radiation the patient receives.
The bigger the patient, the more radiation you’ll require.
The smaller the patient, the less radiation you’ll require.

26. IQ Scan Modes

27. IQ Patient Thickness 12-15 cm is Medium 750 15-22 cm is Fast 3000
Most patients fall in the Fast 3000 range.

28. Bone Densitometry
In preventing Fxs it is the worst scenario that matters.
Generally a slight increase in density as descend the L spine. Approx 6% increase between L1 and L4.

29. Typical Spine scan

30. What’s wrong with this scan?

31. What’s wrong with this scan?
L1 is really T12

32. What’s wrong with this scan?

33. What’s wrong with this scan?
Divisions don’t account for scoliosis

34. What’s wrong with this scan?
Everything

35. DEXA Femur check list Hints for a good scan.
Patient should be straight on table.
Pack patient with rice bags.
Shaft of femur should be straight.
Rotate leg inward, this will hide the lesser Trochanter.

36. DEXA Femur check list Hints for a good scan.
The Wards area is roughly half the neck area
Trochanteric area 8-14cm2 in women, 10-16cm2 in men
Check left and right and state side being used in report.

37. nonIQ DPX scanning Show 15-30 scan lines prior to seeing ischium.
There should be little or no lesser Trochanter.
Straight shaft.
25 lines or more above the Greater Trochanter.

38. Typical Femur Scan

39. What’s wrong with this scan?

40. What’s wrong with this scan?
Too much shaft

41. What’s wrong with this scan?

42. What’s wrong with this scan?
Insufficient tissue below neck

43. What’s wrong with this scan?
Set up for wrong leg

44. What’s wrong with this scan?

45. Bone Densitometry WHO uses T scores
Normal
> -1 SD below young adult
Osteopenia SD
Osteoporosis
<-2.5 SD
Established Osteoporosis
+ Fxs, usually spine, hip, proximal humerus, wrist, rib

46. Template

47. Bone Densitometry Never round up figures
-1 is osteopenia, is normal
-2.5 is osteoporosis, is osteopenia

48. Bone mass in healthy children
Increases with age, weight and pubertal Tanner stage.
Tanner stage and weight are best predictors of bone mass.
Age, sex, race, activity and diet are not good predictors, when weight and Tanner stage are controlled.
Radiology 1991;179:

49. Bone mass in healthy children
Make sure we have at least the age and weight of the child, if not the Tanner stage.
Radiology 1991;179:

50. BMD in children
and adolescents

51. BMD in children and adolescents
Girls

52. BMD in children and adolescents
Males

53. Bone Densitometry
T score is compared to reference population, years, same sex, any race, any weight.
Z score is matched for age, sex, weight and ethnicity.

54. Two possible reasons for this lady’s Z score being
worse than the T score?

55. Two possible reasons for this lady’s Z score being
worse than the T score? Obesity and race

56. The T score is based on a white, same sex, age 20-40 population
The T score is based on a white, same sex, age population. The patient's BMD is compared to this population's BMD. A lower T score means that the patient BMD is low compared to this young, healthy normal weight population The Z score compares the patient to an adjusted population, it adjusts for age, weight, and ethnic background. The Z score can be lower for the patient, if the average patient in this population has a higher BMD than the average in the T score population. This can be seen in patients with higher weights, (which increases bone density), and in African American groups, (which show increased bone density).
If the patients comparison group has a generally higher bone density, then it is possible to have a poorer comparison to others of same age, than to younger comparisons in generally lower density group.

57. 260 lb man, young Z above young T

58. Black as
Black as
White

59. Black as
Black as
White
T same
Z up

60. Bone Densitometry Weight gain/loss and Z
Weight gain (or loss) will not affect Z score comparison, since Z scores are weight matched.but should cause an increase (or decrease) in absolute BMD.
An increase in weight, pushes up the reference range, and therefore the Z score may seem reduced, and vice versa.
2.2lbs=1Kg

61. Bone Densitometry Weight gain/loss and T
Weight gain (or loss) should cause an increase (or decrease) in absolute BMD.
Weight gain (or loss) will affect T score comparison, since reference range will not have changed.
Hence an increase in weight with a corresponding increase in bone density, will look like a good improvement in T score, but fracture risk is unchanged.

62. 51F
90Kg
53F
51Kg

63. = significant increase in fracture risk
1.172
1.176
SD = 0.1 both between -2 and -3
1Y, 16lb gain, 5% BMD loss
= significant increase in fracture risk

64. Bone Densitometry Comparison with previous
Are the studies comparable
Always compare like with like
Thornton L1-4
4th and Lewis L2-4
Any intervening events
Cannot compare Hologic and Lunar

65. Bone Densitometry Comparison with previous
David Sartoris’s previous studies that do not mention the region or levels measured, were standardized for L1-4 and the femoral neck.
He usually did not quote BMD.
Many previous studies were prior to the current database.
Use the percent young adult as a guide to percentage change.

66. Bone Densitometry Comparison with previous
If over a period of time there is an increase in BMD in the lower lumbar spine and decrease in the upper lumbar spine, it is likely there is OA of the lower facet joints, and the upper lumbar spine is a truer reflection of useful BMD.

67. Bone Densitometry Comparison with previous
Increase in BMD of the femoral neck can be due to calcar buttressing with OA of the hip.

68. Bone Densitometry Comparison with previous
If you want to eyeball the % for a comparison, use the young adult since the reference range will not change with age.
A static bone density is actually a good result over a significant period of time
If a test is 1% precise, then a change has to be greater than 2% to be significant

69. Bone Densitometry Comparison with previous
If you would have expected the bone density to have fallen 4% in 2 years, and it is static, then this is a positive response to RX

70. Bone Densitometry Comparison with previous
Generally Rx affects all levels equally. OA does not.

71. Cases

72. 63F

73. 63F

74. 63F

75. 63F

76. 63F

77. 63

78. 63F

79. 63F

80. Report
Because of the previous laminectomy at L4, which may also be affecting the reading on the inferior aspect of L3, the BMD is averaged at L1-2. Note is also made of mild decrease in the L4 vertebral height.

81. 35F White 242lbs 62in

82. 35F White 242lbs 62in

83. 35F White 242lbs 62in

84. Report
Because of the patients weight, the T score may not fully represent the fracture risk, and note should be made that the Z score is xSD below age and weight matched.

85. 39M
.1551

86. 39M OGI
.1551

87. 46 F
Calcified bile

88. 46 F
Calcified bile

89. 46 F Calcified bile

90. 47F
Black

91. 49F 2Y8M gap Lx spine up, Fem neck down

92. 49F

93. T
49F Sacral agenesis

94. 50F

95. 50F dense R femoral neck

96. 50F dense R femoral neck

97. 2d earlier
51F
2d later

98. 2d earlier
51F
2d later

99. 51F
Barium in diverticulum from recent enema

100. 53F
51Kg
47F
59Kg

101. 53F
51Kg
6 yr later, 8Kg wt loss
47F
59Kg

102. 47F
59Kg
53F
51Kg

103. 60F

104. 60F

105. 60F OA

106. 54M
ESLD
s/p trans
Rec. repeat

107. 76F
response to Rx
15m earlier
15m later

108. 85M
Bil THR

109. 85M
Bil THR