A 37-year-old man inverted his ankle while playing basketball with his teenagers in their driveway. He felt a pop and had immediate pain. He had tenderness over the base of his fifth metatarsal. Having met the Ottawa ankle rules for radiographs (see later), a radiograph was obtained, which revealed a nondisplaced fracture at the base of the fifth metatarsal (Figure 106-1).
Fifth metatarsal tuberosity avulsion fracture (dancer fracture). (Reproduced with permission from Simon RR, Sherman SC, Koenigsknecht SJ. Emergency Orthopedics, 5th ed. New York, NY: McGraw-Hill Education; 2007.)
Most metatarsal fractures involve the fifth metatarsal and include avulsion fractures at the base, acute diaphyseal fractures (Jones fracture), and diaphyseal stress fractures. Fractures of the first through fourth metatarsals are less common but can be associated with a Lisfranc injury. Diagnosis is based on the mechanism of injury or type of overuse activity and radiographic appearance. Treatment depends on the type of fracture. Most metatarsal fractures have a good prognosis; however, Jones fractures have a high rate of nonunion, and Lisfranc injuries can result in chronic symptoms.
Avulsion fracture at base of fifth metatarsal: fifth metatarsal tuberosity fracture, dancer fracture, pseudo-Jones fracture.
Jones fracture: acute diaphyseal fracture of the fifth metatarsal.
Foot fractures are common injuries among recreational and serious athletes; however, incidence and prevalence in most populations is unknown.
In women older than age 70 years, the incidence of foot fractures is 3.1 per 1000 woman-years, and more than 50% of these are fifth metatarsal fractures.1
Fifty percent of metatarsal fractures in adults ages 16 to 75 years involve the fifth metatarsal.2
The majority of fifth metatarsal fractures are avulsion injuries (see Figure 106-1).
Twenty-three percent of elite military personnel sustain metatarsal stress fractures; most of these occur after 6 months of training.3
ETIOLOGY AND PATHOPHYSIOLOGY
Avulsion fractures result when the peroneus brevis tendon and the lateral plantar fascia pull off the base of the fifth metatarsal, typically during an inversion injury while the foot is in plantar flexion.
Jones (acute diaphyseal) fracture results from landing on the outside of the foot with the foot plantar flexed.
Diaphyseal stress fractures are caused by chronic stress from activities such as jumping and marching.
Fractures of the first through fourth metatarsals are caused by direct blows or falling forward over a plantar-flexed foot. These fractures may be associated with a Lisfranc injury.
The diagnosis of avulsion or Jones fractures is made on plain radiographs in a patient with a history of injury and acute lateral foot pain. Diaphyseal stress fractures may require CT imaging.