An older patient falls, cannot weight-bear comfortably, and the anteroposterior pelvis and lateral hip films are read as normal. Discharged with analgesia, a proportion return days later with a displaced femoral neck fracture that was undisplaced and fixable on the first visit. The difference between a screw fixation and a hemiarthroplasty is often that missed film.
Some things help before any further imaging. Look at the lesser trochanter on the anteroposterior view: a prominent, fully profiled lesser trochanter means the leg is externally rotated, which in a patient with hip pain is a positive sign rather than a positioning artefact. Follow the trabecular lines across the femoral neck and compare them with the other side; an undisplaced fracture usually shows a break or a step in that pattern before it shows a lucent line. Check Shenton's line is smooth. Ask for a true lateral rather than accepting a frog-leg view, which rotates the neck out of profile.
If the patient cannot straight-leg raise or cannot bear weight and the films are normal, the films are wrong until proven otherwise. Magnetic resonance imaging is the test — it detects the marrow oedema of an incomplete fracture that computed tomography can miss, and it will also show the pubic ramus fracture or the greater trochanteric avulsion that explains the pain instead. Where magnetic resonance imaging is not available the same day, keep the patient non-weight-bearing and repeat the films rather than discharging.
- Treat inability to weight-bear or straight-leg raise with normal films as an indication for magnetic resonance imaging, not reassurance
- Check the lesser trochanter profile — external rotation on the film is a sign, not a positioning error
- Trace the femoral neck trabeculae and Shenton's line and compare with the contralateral side
- Ask for a true lateral; a frog-leg view can hide an undisplaced neck fracture
- If imaging must wait, keep the patient non-weight-bearing and admitted rather than discharged with analgesia
Why it matters
The undisplaced femoral neck fracture that is missed becomes the displaced one that needs a replacement instead of two screws.
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