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.
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.
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.
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.
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.
