Avulsion fractures of the 5th metatarsal tuberosity or styloid process are one of the more common foot avulsion injuries and account for over 90% of fractures of the base of the 5th metatarsal.
On this page:
Terminology
The terms ‘tuberosity’ and ‘styloid process’ are synonyms and refer to the portion of the fifth metatarsal proximal to the inter-metatarsal joint. The confusing term ‘pseudo-Jones fracture’ is also used to refer to these avulsion fractures and is superfluous since ‘avulsion fracture of the fifth metatarsal tuberosity’ perfectly describes the mechanism and anatomical location.
The distinction is clinically important; Jones fractures and stress fractures of the fifth metatarsal often heal poorly due to an insufficient blood supply.
The term ‘dancer’s fracture’ is sometimes used to refer to an avulsion fracture but is best avoided: the original Jones fracture was sustained while dancing and the term is also used to refer to a shaft fracture.
Pathology
The lateral band of the plantar aponeurosis (fascia) is attached to the plantar aspect of the tuberosity 2 and the peroneus brevis tendon inserts into the lateral aspect; both probably contribute to the avulsion injury which is caused by a combination of plantarflexion of the forefoot and forced inversion of the hindfoot. This can occur when running on an uneven surface or when landing awkwardly from a jump.
The fifth metatarsal base should be included in the lateral projection of a trauma ankle series and is an important review area, especially because specific symptoms may be absent.
Radiographic features
Avulsion fractures of the tuberosity of the 5th metatarsal are typically oriented transversely in contrast to the unfused apophysis in children which parallels the shaft. The fracture may reach the cuboid-metatarsal joint.
Treatment and prognosis
These fractures can usually be treated conservatively and commonly heal well due to the robust blood supply 2. Functional weight-bearing in a Robert Jones bandage or elastic strapping together with stiff-soled shoes gives better outcomes compared to immobilization 5. Delayed union may occur in older adults, noncompliant patients and in patients with diabetes or peripheral vascular disease.
Follow-up radiographs between 2 and 4 weeks commonly demonstrate osteoclastic resorption which widens the fracture line; this should not be mistaken for displacement.
Large or displaced fragments with intra-articular extension can be fixed surgically.
Differential diagnosis
Other fractures of the proximal fifth metatarsal and normal structures:
Jones fracture: level with the fourth-fifth inter-metatarsal articulation
stress fracture of the 5th metatarsal: in the proximal diaphysis distal to the level of the fourth-fifth inter-metatarsal articulation
os peroneum, corticated
os vesalianum pedis, corticated
normal apophysis of the proximal 5th metatarsal, seen between 10 and 16 years of age
Unable to process the form. Check for errors and try again.