Transcript Document

Gerrit Engelbrecht
Definitions
 Osteopenia
 Poverty of bone
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Decreased quality or quantity of bone
 Radiologically identified as radiolucency
 Causes
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Diffuse
Regional osteopenia
 Osteosclerosis
 Increased density of bone
Diffuse osteopenia
 Osteoporosis
 osteomalacia
 hyperparathyroidism
 multiple myeloma
 diffuse metastases
 drugs,mastocytosis
 osteogenesis imperfecta
Regional osteopenia
 Disuse osteoporosis / atrophy
 Etiology: local immobilization secondary to
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(a) fracture (more pronounced distal to fracture site)
(b) neural paralysis
(c) muscular paralysis
 Reflex sympathetic dystrophy = Sudeck dystrophy
 Regional migratory osteoporosis, transient regional
osteoporosis of hip
 Rheumatologic disorders
 Infection: osteomyelitis, tuberculosis
 Osteolytic tumor
 Lytic phase of Paget disease
 Early phase of bone infarct and hemorrhage
 Burns + frostbite
Osteosclerosis
 Diffuse Osteosclerosis
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Metastases
Myelofibrosis
Mastocytosis
Melorheostosis
Metabolic: hypervitaminosis
D, fluorosis, hypothyroidism,
phosphorus poisoning
Sickle cell disease
Tuberous sclerosis
Pyknodysostosis, Paget disease
Renal osteodystrophy
Osteopetrosis
Fluorosis
 Constitutional Sclerosing
Bone Disease
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Engelmann-Camurati disease
Infantile cortical hyperostosis
Melorheostosis
Osteopathia striata
Osteopetrosis
Osteopoikilosis
Pachydermoperiostosis
Pyknodysostosis
Van Buchem disease
Williams syndrome
Osteoporosis
WHO
 Osteoporosis, the most
common of all metabolic
bone disorders, is defined by
the World Health
Organization (WHO) as “a
skeletal disease,
characterized by low bone
mass and micro-architectural
deterioration of bone tissue,
with a consequent increase in
bone fragility and
susceptibility to fracture”
 Reduced bone mass of
normal composition
secondary to
 osteoclastic resorption (85
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trabecular,
endosteal,
intracortical
subperiosteal
 osteocytic resorption (15%)
Etiology of osteoporosis
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A. CONGENITAL DISORDERS
B. IDIOPATHIC
C. NUTRITIONAL DISTURBANCES
D. ENDOCRINOPATHY
E. RENAL OSTEODYSTROPHY
F. IMMOBILIZATION
G. COLLAGEN DISEASE, RHEUMATOID ARTHRITIS
H. BONE MARROW REPLACEMENT
I. DRUG THERAPY
J. RADIATION THERAPY
K. LOCALIZED OSTEOPOROSIS
Role of diagnostic imaging
 Two principal aims:
 Identify the presence of osteoporosis
 Quantify bone mass with use of:
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Semiquantitative (conventional radiography)
Quantitative (densitometry) methods.
Conventional radiography
 Radiologic appearance stay the same whatever the
cause.
 Most common modality to diagnose osteoporosis
 Drawback: Start picking up bone loss at 30 % and
more
Generalized osteoporosis
 Increased radiolucency
 Cause: resorption and
thinning of trabeculae
 Trabeculae respond
faster to metabolic bone
changes
 Prominent
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Axial skeleton
Ends of long bones
 Cortical thinning
 Cause: osseous
resorption
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Endosteal
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Intracortical
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Scalloping
Longitudinal striations(
cortical tunneling )
Periosteal
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Irregular definition of the
outer bone surface(Most
specific for high bone
turnover)
Osteoporosis in the axial skeleton
 Picture framing ( loss of the trabeculae in relation to
cortex )
 Loss of horizontal trabeculae
 Compression fractures
 Usually lumbothoracic junction
 Number
 Degree
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Wedge ( anterior height reduce > 4mm : posterior height )
Endplate ( midheight : posterior height )
Crush ( all the heights in relation to neighbouring vertebrae)
Osteoporosis in a vertebrae
• Radiolucency
• Well demarcated
cortical rim
• Verticalization of
trabeculae
Saville index
Genant fracture definition
 Vertebral deformity between T4 and L4
 Height loss > 20 %
 Area reduction 10-20 %
Genant scoring system
 Severity index of vertebral fractures
 Grades:
 Grade 0: No fracture
 Grade 1: Mild fracture ( 20 -25 %reduction in height
compared to neighbouring vertebrae )
 Grade 2: Moderate fracture ( 25 -40 % reduction )
 Grade 3: Severe fracture ( > 40 % )
 Index = Sum Grades/ Number of vertebrae
Point to remember
 Isolated fractures above the T7 level are rare in
osteoporosis and should alert clinicians to a cause
other than osteoporosis
Genant ( semiquantitative)
Examples of wedge fractures
Appendicular skeleton
 Changes first apparent : Ends of long and tubular
bones
 Main sites:
 Hand
 Proximal femur
 Calcaneus
Hand
 Metacarpal bones ( second, third and fourth )
 Corticomedullar index
 Second metacarpal ( accurate)
 Longest established quantitative methods ( > 70 years)
 Automated ( digital x-ray radiogrammetry)-2001
 Converted to BMD
 High reproducibility
 Capacity to help predict future fracture
 Potential to provide a simple, widely available, and
inexpensive method of assessing patients who are at risk for
osteopenia or osteoporosis and might appropriately be
referred for central DXA
Trabecula of the femur
Jhamaria
calcaneal
index
Dual – energy Absorptiometry(DXA)
In 1994, the WHO defined the
threshold levels for the diagnosis of
osteopenia and osteoporosis with
DXA.
As a consequence, DXA
measurements are currently the
standard of reference for the clinical
diagnosis of osteoporosis with bone
densitometry.
Principles of DXA
 Mobile x-ray source
 Two different photon
energies ( constant and
pulsed )
 Attenuation difference
between the soft tissue
and mineralized bone is
used to identify the soft
tissue attentuation
which is then
substracted leaving only
the attentuation values
of the bone
Principles of DXA
 The attenuation is compared to known standard
attenuation values from phantoms => relation
between atenuation and BMD.
 Newer developments lateral scanners
BMD
 Measurements:
 BMD = Bone mineral content ( grams )/Projected area of
the measured site ( cm 2 )
 Overestimation with increased bone size
 Underestimation with decreased bone size
Interpretation of DXA
 BMD expressed in terms of standard deviation
 T score: dev from mean BMD standard young adult
population ( 20- 30 years )
 Z score: Dev. from mean BMD of age and gender
match controls ( NB in 75 years or older )
 WHO( T score in Lumbar spine, proximal femur and
forearm)
Normal
≥ -1.0
Osteopenia
< - 1.0 , > - 2.5
Osteoporosis
≤ - 2.5
Severe osteoporosis
≤ - 2.5
With fragility fracture
 Advantages of DXA
 Low radiation dose
 Low cost
 Ease of use
 Rapidity of measurement
 Limitations
 Two dimensional technique
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Cannot discriminate between cortical and trabecular bone
Cannot discriminate between geometry and increased bone
density
Axial DXA
 Areas were it can be used
 Lumbar spine
 Proximal femur
 Total hip
 Femoral neck
 Trochanter
 Ward area
 Cannot completely discriminate between patients that have
fractures or not
 The lower the BMD the higher is the risk of a fracture
Pitfalls of DXA
 Scanner and soft ware
 Technologist, patient positioning, analysis of scans
 Patient related artefacts
Pitfalls of DXA
 Proper calibration: Phantoms scanned at least once a week
 Positioning
 Improper centering of the lumbar spine
 Abduction or external rotation of the hip
 Analytical pitfalls
 Spine
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Numbering of vertebrae
Placement of intervertebral markers
Detection of bone edges
 Hip
 Placement of ROI
 Detection of bone edges
Pitfalls of DXA
 Anatomic artefacts
 Degenerative disk disease
 Compression fractures
 Post surgical defects
 Atherosclerotic artefacts
 Motion artefacts
 Medical devices: Prosthesis, cement etc
 Personal belongings and clothes: wallets, coins
 Results from different machines not interchangeable.
Positional problems with DEXA
Normal
External rotation
Degenerative changes
DXA of the lumbar spine
Good scan
Problem scan
Peripheral DXA
 Small portable
scanner
 Distal radius :
predicative of wrist
fractures ( T ≤ -2.5)
 Calcaneus: predicative
of spine fractures ( T 1.0 to – 1.5 )
 Especially in elderly
with degenerative
disease
Fracture Risk Assessment Tool
 Based on
 BMD of the femur neck
 Age
 Sex, height and weight
 Seven clinical risk factors
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Previous fracture
Hip fracture
Current smoking
Glucocorticoid use
RA
Secondary osteoporosis
3 or more unit of alcohol daily
 Enter the name of the scanner
 10 year probability of a major osteoporotic fracture
Quantitative CT
 Separate estimates of
 Cortical BMD
 Trabecular BMD
 True volumetric density in mg/cm3
Axial Quantitative CT
 2 to 4 consecutive vertebrae ( T12 – L4 )
 Commercial CT scanners
 Bone mineral reference standard
 8-10 mm thick slices, parallel to vertebral endplate
 Midplane of each vertebrae
 ROI anterior portion of trabecular bone in vertebral body.
 Automatic edge detection software then takes over and
calculate the correct ROI with anatomical landmarks
 Compare attenuation values to a calibration standard
 Conversion to calcium hydroxy apatite/ cm 3
Values
• Absolute
• T or Z scores
• Race dependant
• Compared to healthy population
Advantages of Axial Quantitative
CT
 Better than DXA at predicting vertebral fractures
 Good sensitivity measurement of age related bone loss
after menopause
 Exclude measurement of structures that does not
contribute to spine mechanical resistance but to BMD
values
 Selective measurement of trabeculae which is the most
metabolic active part of bone and main determinant of
the compressive strength of bone
 Allow evaluation of the macro architecture of the
vertebrae
New developments of quantitative
CT
 Volumetric quantitative CT encompass the entire
object of interest with stacked sections or spiral CT
 BMD of entire structure
 Separate analysis of trabecular and cortical
components
 Dual energy CT is currently used to study the bone
marrow adipocytes for effects of aging, drugs and
disease.
Disadvantages of axial quantitative
CT
 High radiation dose
 Poor precision for objects that is complex instead of
longitudinal.
 High costs
 Operator dependance
 Space
 Limited scanner access.
Peripheral quantitative CT
 Separate accessments of cortical and trabecular bone
 Bone geometry at appendicular sites.
 Indexes of bone stability in response to bending and
torsion which are the most important biomechanical
measures of susceptibility fracture and may improve
accuracy in the prediction of fractures.
Peripheral quantitative CT
Peripheral quantitative CT
Peripheral quantitative CT
Morphometry
 Digitising
vertebral height
 Ratios compared
to normal values
 > 15 % abnormal
 Cannot
differentiate
from other
reason for
deformities (
degeneration,
congenital)
Ultrasound
 Screening tool with confirmation by DXA
 Not sensitive enough for long term followup of
osteoporosis.
 Calcaneus, distal metaphysis of the phalanx, radius
and tibia
Newer advances
 Aim to better identify the macro and micro anatomy of
bone to improve prediction of fracture risk.( imaging of
trabeculae )
 MRI
 3 tesla systems
 Calcaneus, knee and wrist
 Several studies but no clinical guidelines yet
 CT
 clinical systems not yet able to detect true trabecular
networks but the texture
 Micro CT with resolutions of 6 micrometer currently used
with in vitro studies.
CT
MRI
References
 Ortopedic imaging, A practical approach, Adam
Greenspan
 Fundamentals of Diagnostic Radiology, Brant and
Helms
 Integrated imaging approach to osteoporosis: State of
the art review and update. Guiseppe Guglielmi et al,
Radiographics 2011; 31:1343
 The trabecular pattern of the calcaneus as index of
osteoporosis; NL Jhamaria et al., British editorial
society of bone and joint surgery, vol 65-B, No2 March
1983