Musculoskeletal X-ray - General principles
Viewing principles

Key points

  • 2 views are better than 1
  • Check all available images
  • Compare with the other side (if imaged)
  • If available ALWAYS compare with old X-rays

Confidence in assessing musculoskeletal system X-rays comes from experience and a knowledge of normal appearances. All patients are different, so being sure of the distinction between normal and abnormal is often difficult.

Here are some principles that may help you to determine if a finding is normal.

2 views

In the context of trauma at least 2 views of the body part in question are usually required. If looking for specific disease entities, for example erosions in rheumatoid arthritis, this may be less important. In some cases, such as possible scaphoid injury, more than 2 images are required.

2 views are better than 1

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2 views are better than 1

  • The Anterior-Posterior (AP) view shows only minor cortical bone irregularity
  • The Lateral view shows an obvious bone injury

Clinical information

  • Twisting injury to left ankle
  • Patient unable to bear weight
  • Lateral malleolus bone tenderness

Diagnosis

  • Oblique fracture of the distal fibula at the level of the ankle joint
  • (Weber type B injury)

Compare with other side

Images of the asymptomatic contralateral side to a suspected abnormality are not routinely acquired for assessment of all bones or joints.

If an old image of the contralateral side is available, or if the other side is included as standard (for example hip/pelvis), then comparison between symptomatic and asymptomatic appearances can be very helpful.

Right v left example - Pelvis and hips

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Right v left example - Pelvis and hips

  • This image of the pelvis shows subtle irregularity of the cortical outline of the right femoral neck
  • Comparison with the other side - which is asymptomatic - increases confidence of a genuine abnormality
  • There is also loss of the normal trabecular pattern indicating a fracture (#)

Clinical information

  • Right groin pain after a fall
  • Shortened and externally rotated right leg

Diagnosis

  • Fractured neck of right femur

Compare current with previous images

The 'old X-ray' is said to be the 'cheapest test in radiology.'

If you are uncertain of an abnormality and there is an old image available of the area in question, then ALWAYS look at it. Doing this often increases diagnostic confidence, and can show progression of pathology over time.

New v old

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New v old

  • The current X-ray shows an obvious displaced fracture(#) of the femoral shaft
  • The old X-ray demonstrates the cause of the fracture - the bone has been weakened by a lytic bone lesion

Clinical information

  • Minor trauma to the thigh area - (femoral shaft fractures are usually the result of extreme force)

Diagnosis

  • Metastatic disease of bone with pathological femoral shaft fracture

Keep your eye on the ball

When looking at an X-ray always keep the current clinical features at the forefront of your mind.

Remember - 'Treat the patient and not the X-ray!'

Keep your eye on the ball

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Keep your eye on the ball

  • Large calcified uterine fibroid
  • Loss of normal cortical contour of the femoral neck

Clinical information

  • Elderly woman - mechanical fall
  • Right hip pain
  • Shortened and externally rotated right leg

Diagnosis

  • Fractured neck of right femur (#)
  • Asymptomatic incidental uterine fibroid

Look for the unexpected

Not all disease that presents with musculoskeletal symptoms is primarily related to pathology of the bones or joints. Very often pain is referred to the symptomatic area and is explained by disease of another system.

For example, shoulder pain is usually due to shoulder pathology, but always keep in mind that pain may be referred to the shoulder from the cervical spine, brachial plexus or diaphragm.

Look for the unexpected

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Look for the unexpected

  • Minor narrowing of the subacromial space (arrowheads) - suggesting rotator cuff disease which is a very common cause of shoulder pain
  • It would be easy to consider this the only abnormality if not checking the image systematically
  • Unexpected apical lung mass!

Clinical information

  • Clinically suspected rotator cuff disease
  • Pain distal to the elbow - rarely if ever caused by shoulder pathology

Diagnosis

  • Minor rotator cuff disease
  • 'Pancoast' tumour - apical lung cancer (cause of distal pain - referred from brachial plexus)

Image quality

The acquisition of many X-ray images requires careful patient positioning which may not be possible due to pain or reduced patient co-operation. High quality images may not be achievable, in which case you will have to work with the images provided. If an image is sub-optimal you can ask the radiographer if there were particular technical reasons for this. Requesting a repeat image may be reasonable, if clinically justified.

Artifact

Musculoskeletal system X-rays may demonstrate internal artifact, for example due to previous orthopaedic surgery or foreign bodies relating to an injury.

If there is external artifact that obscures the area of anatomical interest, then if possible this should be removed.

Artifact

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Artifact

  • Metallic bangles were not removed prior to acquiring the X-ray
  • The carpal bones are obscured

Clinical information

  • Wrist pain after a fall
  • Suspected carpal bone fracture

Diagnosis

  • The jewellery artifact makes it impossible to exclude bone injury