What causes a nutcracker fracture on foot radiography and CT?
Let me know in the comments.
Click to reveal the answer
Answer:
A nutcracker fracture is a compression fracture of the cuboid, crushed between the anterior process of the calcaneus behind and the bases of the fourth and fifth metatarsals in front. The mechanism is forced abduction of the forefoot with axial loading and midfoot plantar flexion, classically in a fall from horseback with the foot caught in the stirrup, and also in sport and road traffic injury. It is rarely isolated: it belongs to a complex midfoot injury pattern and is commonly accompanied by medial column injury, navicular or cuneiform fracture and Lisfranc disruption, so the whole midfoot must be assessed. Radiographs in AP, lateral and 45-degree oblique projections may show comminution, articular incongruity and, importantly, shortening of the lateral column, but they underestimate the injury; CT is mandatory to define articular displacement and plan fixation, because unrestored lateral column length leads to painful planovalgus deformity and midtarsal arthritis. It is unrelated to nutcracker syndrome, compression of the left renal vein between the aorta and the superior mesenteric artery.
Why is it called so?
The cuboid is crushed between the calcaneus and the metatarsal bases as a nut is cracked between the two arms of a nutcracker.
Pathophysiology
The cuboid is the keystone of the lateral column of the foot, articulating with the calcaneus proximally and the fourth and fifth metatarsals distally. Forced forefoot abduction swings the distal lateral column laterally while the hindfoot is fixed, so the two articulating surfaces are driven towards each other with the cuboid interposed. Axial load through the lateral column at the same moment converts this into a direct crushing force, and the relatively soft cancellous bone of the cuboid impacts and comminutes, losing height. Because the lateral column is thereby shortened, the forefoot abducts further and the medial column is stressed, which is why associated medial injuries are the rule rather than the exception.
Alternative names: Cuboid nutcracker fracture, lateral column compression fracture
Other associated named signs: Lisfranc injury and the fleck sign, and the Chopart fracture-dislocation
References
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
Improve Content And Help Your Colleagues!
Found an error in the post? Please let us know using our contact page and we will update it with due credits!
If you wish to contribute radiological images for this case (or any other article on the website), you can submit them here and you will be duly credited: Submit radiology case