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)

http://medgen.genetics.utah.edu/photographs/diseases/high/peri220.jpg

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