Imaging Studies in Orthopaedics

1
Chapter 31

• Imaging Studies in Orthopaedics

2
Overview

• 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

3
Imaging Studies

• 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)

4
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.

5
Radiology

• 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

6
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

7
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

8
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

9
Radiology

• Contrast-enhanced radiography procedures involve
  the use of a contrasting agent to highlight
  different structures. Examples include
• Arthrography
• Angiography

10
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

11
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

12
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

13
CT Myelogram

• A diagnostic tool that uses radiographic contrast
  media (dye) to illuminate the spinal canal, cord,
  and nerve roots during imaging

14
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

15
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

16
Diagnostic Ultrasound

• 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

17
Radionuclide Scanning

• 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