Fifth metatarsal base fractures

• Commonest fracture of the lower limb.
• Tuberosity fractures:The commonest form. Secondary to an inversion injury in the plantar flexed foot. Originally thought to be an avulsion fracture at the site of insertion of peroneus brevis, although more recently the lateral band of the plantar aponeurosis has been implicated. The types of injury ranges from a small avulsion to fracture of the entire tuberosity.
• Jones’ fracture: Diaphyseal fracture occurs approximately 1.5cm from the base (metaphyseal–diaphyseal junction). More serious than tuberosity fractures. Usually caused by combination of forces produced during running or jumping.
• Always look at the base of 5th metatarsal in an ankle view.
• The fracture line appears transverse at right angles to the axis of the metatarsal.
• If the fragment is small, the fracture will often involve the joint with the cuboid.
• Fragment separation may be evident.
• A Jones’ fracture classically extends into the inter-metatarsal joint.
• Never be confused with the epiphyseal plate in children. This is aligned parallel to the shaft.With this in mind a fracture through the epiphysis can occur.

Fifth metatarsal base fractures.(A) Base of 5th metatarsal fracture.

(B) Partial avulsion of the apophysis at the base of 5th metatarsal.

(C) Always remember to examine the base of the 5th metatarsal on an ankle X-ray.

(D) Spiral fracture of the fifth metatarsal bone.