Conventional radiography

Conventional radiography

• Bone fractures

• Eliminates bone fractures

• Each film involves irradiation, but generally low dose

• Static images

Conventional radiography is without doubt the most cost-effective and simple way of diagnosing acute fractures. It is also the most specific investigation. It is not, however, the most sensitive so that if a fracture is still clinically suspected in the presence of an apparently normal radiograph further investigation should be

Questions the clinician should ask when considering imaging:

• What is the problem to be solved?

• Is quantification/classification needed?

• Will the imaging result influence treatment?

Table 5.1.2 Survey of indications for diagnostic imaging.

Ordinary X-ray

CT scan

MR scan

Ultrasound

Scintigraphy

Price

x

xx

xxxx

x

x

Waiting time

Low

Moderate

High

Low-moderate

Low-moderate

Bones

Ordinary fractures

+++

If problems

+++(special)

Comminuted or complex fractures

++

+++

Osteochondral fractures

+

+

+++

++

Stress fractures

+

(+)

+++

+++

Shin splints

++

+++

Vascularization

?

+++

Joints

Arthritis

++

+++

++

Meniscus

+++

+

+

Collateral ligaments

+++

++

Cruciate ligaments

+++

+

Cartilage injury

++

Osteochondritis

+

++

+++

++

Coalitio

++

+++

Menisceal cyst

++

+++

Ganglions

++

+++

Baker's cyst

++

+++

Inflammation

++(?)

++

++

Labral injuries

++

++

++

Hill-Sachs lesions

++

+++

Muscle/tendon

Sprain—acute

++

+++

Sprain—chronic

+

+++

Bursitis—acute

+++

+++

Bursitis—chronic

++

+++

Tendon ruptures

+++

+++

Enthesopathies

?

?

++

Myotendinitis

+

+++

Myositis ossificans

++

+

+

+++

+++

considered. The X-ray beam needs to be tangential to an abnormality for it to be visible. Conventionally only two radiographic views tend to be performed: usually a lateral and frontal projection (using an X-ray beam passing either from the front to the back of the patient, i.e. anteroposterior—AP, or from the back to the front, i.e. posteroanterior—PA). Using such orthogonal projections will normally demonstrate most fractures. If the bony anatomy is complex, as occurs in the spine and joints, then fractures may be obscured by overlying bone. Similarly if the structure is cylindrical, as is the case with many bones, small structures such as avulsed bone fragments may be missed as the beam may not be tangential to it if only two projections are used. In such circumstances additional oblique projections may be helpful or alternatively a tomographic technique may be successfully used, e.g. conventional linear tomography, computed tomography (CT), MRI or ultrasound imaging.

Conventional radiographs are also poor at demonstrating marrow pathology as they rely on alteration to cortices or a large area of spongiosa in order for the abnormality to be conspicuous. This inability to demonstrate bone marrow or periosteal edema means that radiographs are only able to demonstrate stress fractures or osteochondritis at a relatively late stage, i.e. when there is cortical breakdown or subchondral bone fragmentation or if sufficient time has occurred for an osteoblastic repair response to have taken place. Accordingly correctly tailored MR imaging is more appropriate for demonstrating these conditions early in their evolution.

Joint radiographs are able to demonstrate degenerative arthrosis but again usually only at a late stage in its evolution. The classical radiographic diagnostic signs are loss of joint space, subchondral cyst formation, marginal osteophytosis and subchondral sclerosis. All of these features when present usually reflect disease of reasonably long duration.

In cases of tarsal coalition specific oblique radiographic projections will often confirm the presence of bony (but not fibrous) bars. In many cases, however, CT or occasionally MR imaging is required for a definitive diagnosis.

Conventional radiographs are good at demonstrating established myositis ossificans but of limited use early in its evolution. The fact that US demonstrates the condition at an earlier phase may be helpful in terms of treatment. If myositis ossificans is present on US then a radiograph should be obtained. If the radiograph is positive then it confirms the diagnosis. If it is negative then the calcification is early and presumably more susceptible to benefit from therapies aimed at halting its progress.

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