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Diagnostic Imaging of Bones and Joints
Introduction to Orthopedic Radiology
Why PT’s Need to Know About Medical Imaging
To correctly interpret radiologists written report
To speak the same language as physiciansTo enhance awareness of patients conditionRadiologist 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
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.
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
BODY COMPOSITION
AIR: Black
Examples- trachea, lungs, stomach,
digestive tract
FAT: Gray black
Examples- subcutaneously along
muscle sheaths; around
viscera
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.)
Continued
BONE: Gray/White
CONTRAST MEDIUM: White Outline
HEAVY METALS: White Solid
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
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
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)
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
Continued
Contrast: Difference between adjacent images. It is controlled by adjusting the energy of the beam.
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
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
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
10 yo male normal AP and mortise view
REMODELING OF BONEWOLFF’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
ABC’S OF VIEWING FILMSA: 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)
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
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.
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
C. CARTILAGE SPACES
1. Assess joint space width
2. Assess subchondral bone
3. Assess the epiphysis and growth
plates
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)
XRAYS
Lateral view
AP View
Sunrise view
AP Ankle xray
Lateral View
Oblique
