Diagnostic Imaging of Bones and Joints

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Diagnostic Imaging of Bones and Joints

• Introduction to Orthopedic Radiology

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Why PTs Need to Know About Medical Imaging

• To correctly interpret radiologists written
  report
• To speak the same language as physicians
• To enhance awareness of patients condition
• Radiologist reports are often written for the
  MDs and may not take into account information
  the PT needs to treat the patient and to
  adequately formulate a prognosis

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Important Facts About Xrays

• Plain film radiography remains as the 1rst order
  diagnostic imaging modality
• Xrays are a form of electromagnetic radiation
  similar to visible light but of shorter
  wavelength
• Xray tube generates xrays and beams them toward
  the patient. Some of the energy is absorbed
  rest passes through patient and hits the film
  plate.
• Shades of gray on film are a representation of
  the different densities of the anatomic tissues
  through which the xrays have passed.

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• Tissues with greater density will absorb more of
  the xray so less of the beam reaches the film
  plate. The resultant image is therefore lighter.
  Tissues with less density will allow more xray
  to reach the film so it will be darker. This is
  called radiodensity and is determined by
• composition of the structure
• thickness of the structure

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BODY COMPOSITION

• AIR Black
• Examples- trachea, lungs, stomach,
• digestive tract
• FAT Gray black
• Examples- subcutaneously along
• muscle sheaths
  around
• viscera

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• WATER Gray
• Examples Muscles, nerves, tendons,
• ligaments, vessels
• (All of these structures have the same density
  and therefore are hard to distinguish on plain
  xrays.)

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• BONE Gray/White
• CONTRAST MEDIUM White Outline
• HEAVY METALS White Solid

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PERCEIVING 3 DIMENSIONS

• The center of the xray beam is always
  perpendicular to the film plate. The position of
  the body will determine the outline of the image.
• SEE FIGURES 5 -6

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ROUTINE RADIOLOGIC EVALUATION

• Consists of the angles of projection that best
  demonstrate the anatomy while utilizing the least
  amount of exposures.
• Common Views
• Anteroposterior (AP)
• Lateral (R and L)
• Oblique (R and L)
• (See Figure 7)
• Patient positioning for each projection is
  standardized throughout the USA

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VIEWING RADIOGRAPHS

• In AP and Lateral views, the film is always
  positioned on the view box with the patient
  positioned as if facing the viewer in anatomical
  position.
• Hands and feet are placed with fingers or toes
  pointing up
• Lateral views are placed on the box in the
  direction that the beam traveled.
• Magnetic markers are used for R and L. Use this
  as the reference to place the patient facing the
  viewer in anatomical position (Fig 8)

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FACTORS INFLUENCING QUALITY OF XRAYS

• Detail Geometric sharpness. Can be
  affected by
  movement
• Distortion Difference between the actual
  imagery and the recorded image. Geometric
  distortion occurs as the beam progresses away
  from the perpendicular. Fig. 9

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• Contrast Difference between adjacent images.
  It is controlled by adjusting the energy of the
  beam.

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ANATOMY OF BONE

• Compact Bone forms outer shell or cortex
• of bone dense
• Cancellous Bone forms the inner aspect of
• bone except for the
  marrow
• cavity spongy

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• FIGURE 10
• Periosteum Covers the cortex fibrous layer
  which contains blood vessels, nerves and
  lymphatics.
• Endosteum Membrane lining the inner aspect of
  the cortes and medullary (marrow) cavity
• Diaphysis Shaft
• Metaphysis Flared part at either end of shaft
• Epiphysis Either end of the bone

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PROCESSES OF BONE GROWTH

• Ossification Process of replacing cartilagenous
  model with bone
• Endochondral Ossification How bones grow in
  length
• Intramembraneous Ossification How bones grow in
  width
• Physis The growth plate evidenced by the open
  space Fig 11 and 12

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10 yo male normal AP and mortise view
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REMODELING OF BONE

• WOLFFS LAW
• Bone will be deposited in sites subjected to
  mechanical stress with trabeculae aligning in
  ways that best absorb stress. Bone will resorb
  from sites deprived of stress.
• Clinical Relevance As soon as it is safe,
  weight bearing should be allowed through the bones

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ABCS OF VIEWING FILMS

• A ALIGNMENT
• 1. Assess the size of the bones
  gigantism,
• dwarfism, etc
• 2. Assess the number of bones
• 3. Assess each bone for normal shape
  and
• contour irregularities can be from
  
• trauma, congenital, developmental
  or
• pathological
• 4. Assess joint position trauma,
  inflammatory
• or degenerative disease (Fig 13)

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• B. BONE DENSITY
• 1. Assess general bone density
• contrast between soft tissues
  and bone
• contrast between cortical
  margin and the
• cancellous bone and medullary
  cavity
• loss of contrast means loss of
  bone density
• ie osteoporosis
• labeled as osteopenia,
  demineralization or
• rarefaction

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Originally coined for the changes of senile
osteoporosis, biconcave deformities of the
vertebral bodies ("fish vertebrae") are
characteristic of disorders in which there is
diffuse weakening of the bone. The name is
derived from the actual appearance of a fish
vertebrae which normally has depressions in the
superior and inferior surfaces of each vertebral
body. This sign is typically used for osteopenia.
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• 2. Assess local bone density looking for
  sclerosis
• sign of repair in the bone.
  Excessive sclerosis is
• indicative of DJD. (Fig 15)
• Bone Lesions
• Osteolytic- bone destroying so
  appear radiolucent
• as in RA or Gout
  (Fig 16)
• Osteoblastic- bone forming
  osteoblastomas,
• osteoid
  osteomas
• 3. Assess texture abnormalities looking at
  trabeculae
• 
  appearance

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• C. CARTILAGE SPACES
• 1. Assess joint space width
• 2. Assess subchondral bone
• 3. Assess the epiphysis and growth
• plates

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• s SOFT TISSUES
• 1. Assess the gross size of the musculature
• (Fig 17)
• 2. Assess outline of joint capsules
  normally
• indistinct become obvious during
  episodes
• of increased joint volume from
  infection,
• hemorrhage or inflammation
• 3. Assess the periosteum normally
  indistinct
• (Fig 18)

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XRAYS
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Sunrise view
AP View
Lateral view
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AP Ankle xray
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Lateral View
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Oblique