Avulsion Fracture of Base of 5th Metatarsal & Os Peroneum

Figure: Oblique radiograph of the foot shows a transverse avulsion fracture (arrow) of the 5th metatarsal bone with displacement and extension into the cuboid-metatarsal joint. Note a nearby 'os peroneum' (arrowhead).

Avulsion Fracture of Base of 5th Metatarsal

• Most common fracture at this location
• Usually extra-articular
• Due to sudden contraction of peroneus brevis muscle or lateral band of plantar fascia during inversion
  
• Treated conservatively, unless there is displacement or large fragment involving cuboid-metatarsal joint
  
• Other two types of fractures (at proximal 5th metatarsal) are Jones (AKA fracture at metadiaphyseal junction within 1.5 cm distal to tuberosity of 5th metatarsal), and stress fracture.

Key Things to Include in Report

1. Location (tip, tuberosity, metadiaphyseal junction, diaphysis)(to distinguish between different types of proximal 5th metatarsal fractures)
   
2. Joint involvement (cuboid-metatarsal, 4th-5th intermetatarsal)
3. Displacement

Os Peroneum = ossicle in peroneus longus, seen at the tip of 5th metatarsal base, common

Reference:
Nunley JA. Fractures of the base of the fifth metatarsal. Orthopedic Clinics of North America (January 2001)