The ABCs of Extremity X-Ray Interpretation for NPs

I’ve previously discussed the ABCDEFGHI’s of chest X-ray interpretation, but today wanted to tackle a topic somewhat simpler. Fortunately for nurse practitioners, interpretation of orthopedic extremity X-rays involves fewer steps as there is generally not quite so much anatomy to consider compared with the trunk. While not all NPs interpret their own radiography, it’s still essential to have a basic understanding of how the process works. What exactly should you be looking for when you interpret an extremity X-ray?

When interpreting an extremity X-ray, at the most basic level, remember your ABCs. Here’s a breakdown of the mnemonic.

A – Adequacy and Alignment

The first thing you should analyze with any X-ray is the adequacy of the film. For example, does the image portray the correct side of the body? Is the penetration of the image appropriate? Is there any artifact obscuring the image? If you can’t see what you’re looking at, or are using an image that doesn’t show the entire or correct portion of the anatomy you need to view, the X-ray isn’t going to help you.

When it comes to orthopedics, always get at least two views of the extremity in question (anterior-posterior and lateral). Three views is even better, in some cases essential. Adding an oblique view can help visualize difficult to see fractures and other bony abnormalities that might otherwise have been missed. X-rays aren’t always adequate. CT or MRI may be required to visualize certain orthopedic conditions. Know when more advanced imaging is your best bet.

Finally, assess the alignment of bones. As you look at the relationship of the bones to one another, does anything look out of place? In the case of an orthopedic injury, for example, you may noticed displacement associated with a fracture, or a dislocation (here are some splinting tips if you note an abnormality). Misalignment can also be a result of chronic conditions such as degenerative bone disease.

B – Bones

And now for the obvious – when interpreting an extremity X-ray, assessing the bones is a clear must. As you review the films, pay special attention to the cortical outline of each bone and also look for abnormalities in bone density and texture. A breach in the cortical outline signals a fracture whereas changes in bone density may be a sign of a chronic problem like osteopenia or demineralization. Know how to recognize bony lesions, which may be benign or malignant.

If you note a bony abnormality on an image, don’t stop there. Remember, your patient may have more than one injury or radiographic abnormality. The entire film must be reviewed, even if you note an obvious fracture.

C – Cartilage

While cartilage itself is not readily visible on an X-ray, radiographic imaging does allow for evaluation of joint spaces. Abnormally wide spaces, for example, could signal a ligament injury or distracted fracture. Narrow spaces may be a sign of degenerative processes and thinning cartilage, as in the case of osteoporosis. You must also assess the growth plates in your imaging of pediatric patients. Injuries involving the growth plate are prone to complication and should be carefully treated and followed up closely.

Not sure if the joint spaces look correct on your image? Do a side-by-side comparison. Image the unaffected side of the anatomy. Are the films symmetrical? Comparing images will help you decide what’s normal and what’s not for your patient.

*BONUS: S – Soft Tissue

Finally, check out the soft tissue. Note the size of musculature, any swelling, joint effusion, or other abnormalities like a foreign body. In cases where bony abnormalities aren’t obvious, soft tissue changes like swelling or effusion can clue you in to a problem. This is often the case in elbow injuries and fractures, for example, where a fracture may not be well visualized on X-ray, but a “fat pad sign” or “sail sign” clues you in to a possible intra-articular injury or fracture.