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Chapter 31

Imaging Studies in Orthopaedics

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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 ofphysical therapy practice

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Imaging Studies

The results from imaging studiesshould 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)

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Radiology

The following structures are in order ofdescending density: Metal

Bone. Bone can have varying densities withinthe body. For example, cancellous bone is lessdense than cortical bone, and will thus appearlighter than the cortical bone

Soft tissue

Water or body fluid

Fat

Air. As air is the least dense material in thebody, it absorbs the least amount of x-ray

particles, resulting in the darkest portion of thefilm

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Radiology

Plain-film, or conventional, radiographsare relatively inexpensive and give an

excellent view of cortical bone May be more specific than MRI in

differentiating potential causes of bonylesions

Not considered sensitive to the earlychanges associated with tumors,infections, and some fractures

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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

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Radiology

A stress radiograph is a procedureusing radiographs taken while stress is

applied to a joint Can be helpful in assessing spinal

stability

Video fluoroscopy procedures involvethe use of x-rays to evaluate the

quality and quantity of joint motion

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Radiology

Contrast-enhanced radiography

procedures involve the use of a

contrasting agent to highlight differentstructures. Examples include:

Arthrography

Angiography

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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 ortomographic image

Helpful in the examination of acutefractures, aneurysms, infections,hematomas, cysts and tumors

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Computed Tomography

(CT) Image quality in CT imaging depends on a

variety of factors which are mostly selected

by the operator. Two parameters are usedto 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

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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

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Magnetic Resonance

Imaging (MRI)

MRI images are the result of the

interaction of body tissues withelectromagnetic forces

Commonly used to assess the central

nervous system, and soft tissueinjuries

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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 andphysiologic tissues

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Radionuclide Scanning

Involve the diagnostic use of

radioactive material or isotopes thatare administered orally orintravenously

This test is used to detect particularareas of abnormal metabolic activitywithin a bone