1. Check you have the right views. There are two views in foot x-rays DP (dorsal-plantar) and oblique. Both should ideally be done when weight-bearing if your patient can manage it.
2. Review the bones.
Work round the bones one by one (including the metatarsals). Start proximally and work your way down, going medial lateral. This will ensure you check them all.
3. Find any bits that aren’t attached.
Consider whether any floaty bits might be an ossicle. Pay particular attention to small avulsions from the bones – these are very easy to miss.
There are a couple of common ossicles that you might see:
Os tibiale externum – this is an ossicle present at the medial aspect of the navicular bone (it appears at adolescence)
Os peroneum – this an accessory bone in the peroneus longus tendon
Avulsions commonly occur on:
The lateral aspect of the cuboid
The dorsal surface of navicular and talus (seen only a lateral ankle view)
4. Check the base of fifth.
Most fractures here are avulsions of the metatarsal tuberosity. This is where peroneus brevis attaches and an inversion injury can cause the fracture.
A Jones fracture is a transverse fracture at the proximal shaft of the fifth metatarsal. It is managed differently (non-weight bearing).
Also, don’t confuse a base of fifth fracture with an unfused apophysis or vice versa. An unfused apophysis runs longitudinally, whereas fractures are usually transverse. The apophysis appears at age 12 for boys and age 10 for girls, and it usually fuses over the next few years.
5. Check for calcaneus fractures. Look for an avulsion of the anterior process of the calcaneum (oblique view). Look lateral to the calcaneum where extensor digitorum brevis inserts (on the DP view). You can also get injuries to the anterio-lateral aspect of the calcaneus.
6. Check for Lisfranc injuries. Normally aligned bones should have the second metatarsal aligning with the intermediate cuneiform on the DP view; and the third metatarsal aligning with the lateral cuneiform on the oblique view. The Lisfranc ligament connects the cuneiforms and the second metatarsal. Disruption of this ligament leaves an unstable foot and so it’s an important one not to miss.
To see more about Lisfranc injuries, check out Andy Neill’s great video on this here.
7. Consider stress fractures
These commonly occur on the second or third metatarsals. Sometimes they just present with callous formation or sometimes cannot be seen on plain x-ray and require further imaging (e.g. MRI) to diagnose.