Transcript Document
Gerrit Engelbrecht
Definitions
Osteopenia
Poverty of bone
Decreased quality or quantity of bone
Radiologically identified as radiolucency
Causes
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
(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
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
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
trabecular,
endosteal,
intracortical
subperiosteal
osteocytic resorption (15%)
Etiology of osteoporosis
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:
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
Axial skeleton
Ends of long bones
Cortical thinning
Cause: osseous
resorption
Endosteal
Intracortical
Scalloping
Longitudinal striations(
cortical tunneling )
Periosteal
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
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
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
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
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