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Chapter 31
Imaging Studies in Orthopaedics
Overview
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The availability of diagnostic images to
physical therapists greatly depends on
the practice setting.
Outside of the United States military
health system, the ordering of imaging
studies is not within the scope of
physical therapy practice
Imaging Studies
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The results from imaging studies
should be used in conjunction with
other clinical findings
In general, imaging tests have a high
sensitivity (few false negatives), but
low specificity (high false-positive rate)
Radiology

Conventional (plain film) radiography is
generally considered to be the first order
diagnostic imaging modality.
– X-rays are part of the electromagnetic spectrum
and have the ability to penetrate through body
tissues of varying densities
– Exposure to the x-ray particles causes the film to
darken, while those areas of absorption appear
lighter on the x-ray film or radiograph

The denser a tissue is, the lighter it appears on the
film or radiograph.
Radiology
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The following structures are in order of
descending density:
– Metal
– Bone. Bone can have varying densities within the
body. For example, cancellous bone is less
dense than cortical bone, and will thus appear
lighter than the cortical bone
– Soft tissue
– Water or body fluid
– Fat
– Air. As air is the least dense material in the
body, it absorbs the least amount of x-ray
particles, resulting in the darkest portion of the
film
Radiology

Plain-film, or conventional, radiographs
are relatively inexpensive and give an
excellent view of cortical bone
– May be more specific than MRI in
differentiating potential causes of bony
lesions
– Not considered sensitive to the early
changes associated with tumors,
infections, and some fractures
Radiology

When evaluating radiographs, a
systematic approach such as the
mnemonic ABCS is recommended;
– A = Architecture or alignment
– B = Bone density
– C = Cartilage spaces
– S = Soft tissue evaluation
Radiology

A stress radiograph is a procedure
using radiographs taken while stress is
applied to a joint
– Can be helpful in assessing spinal
stability

Video fluoroscopy procedures involve
the use of x-rays to evaluate the
quality and quantity of joint motion
Radiology

Contrast-enhanced radiography
procedures involve the use of a
contrasting agent to highlight different
structures. Examples include:
– Arthrography
– Angiography
Computed Tomography
(CT)

Also known as computerized axial
tomography (CAT) and computerized
transaxial tomography (CTI).
– Uses a fan-like beam of x-rays to provide
an almost three-dimensional or
tomographic image
– Helpful in the examination of acute
fractures, aneurysms, infections,
hematomas, cysts and tumors
Computed Tomography
(CT)

Image quality in CT imaging depends on a
variety of factors which are mostly selected
by the operator. Two parameters are used to
define the image quality of a given system:
– Spatial resolution: the ability of the system to
distinguish between two closely spaced objects.
– Contrast resolution: the ability of the system to
discriminate between two adjacent areas with
different attenuation values
Computed Tomography
(CT)

CT scan provides good visualization of
the shape, symmetry, and position of
structures by delineating specific areas
– This information can be helpful in the
examination of acute trauma, aneurysms,
infections, hematomas, cysts, and tumors
CT Myelogram

A diagnostic tool that uses
radiographic contrast media (dye) to
illuminate the spinal canal, cord, and
nerve roots during imaging
Magnetic Resonance
Imaging (MRI)


MRI images are the result of the
interaction of body tissues with
electromagnetic forces
Commonly used to assess the central
nervous system, and soft tissue
injuries
Magnetic Resonance
Imaging (MRI)

The advantages of MRI include its
excellent tissue contrast, ability to
provide cross-sectional images,
noninvasive nature, and complete lack
of ionizing radiation. MRI provides an
excellent view of anatomic and
physiologic tissues
Diagnostic Ultrasound

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Based on the transmission of sound
waves through tissue and the time it
takes for the waves to be reflected
back to the transducing probe
Currently used to help detect soft
tissue injuries, tumors, bone
infections, bone mineral density, and
arthropathy
Radionuclide Scanning
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Involve the diagnostic use of
radioactive material or isotopes that
are administered orally or
intravenously
This test is used to detect particular
areas of abnormal metabolic activity
within a bone