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1. Diagnostic Imaging of Bones
and Joints
Introduction to Orthopedic
Radiology

2. Why PT’s 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
MD’s and may not take into account
information the PT needs to treat the patient
and to adequately formulate a prognosis

3. 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.

4.  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

5. BODY COMPOSITION
AIR: Black
Examples- trachea, lungs, stomach,
digestive tract
FAT: Gray black
Examples- subcutaneously along
muscle sheaths; around
viscera

6. Continued
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.)

7. Continued
BONE: Gray/White
CONTRAST MEDIUM: White Outline
HEAVY METALS: White Solid

11. 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

12. 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

13. 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)

15. 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

16. Continued
 Contrast: Difference between adjacent
images. It is controlled by adjusting the
energy of the beam.

17. 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

18. 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

20. 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

22. 10 yo male normal
AP and mortise view

23. REMODELING OF BONE
WOLFF’S 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

24. ABC’S 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)

28. 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

29. 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.

32. 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

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

41. 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)

43. XRAYS

61. Lateral view
AP View
Sunrise view

64. AP Ankle xray

65. Lateral View

66. Oblique