The fifth metatarsal is the most commonly fractured metatarsal. The fifth metatarsal can be divided anatomically into tubercle, base, shaft, head, and neck. Distal fifth metatarsal fractures involve the distal shaft, head, and neck region. Fractures of the base of the fifth metatarsal are more common than distal fractures. Proximal fifth metatarsal fractures are separated into three zones: (zone 1) tuberosity avulsion fracture; (zone 2) Jones fracture; and (zone 3) diaphyseal stress fracture.
Tuberosity avulsion fracture of the fifth metatarsal is also known as the “tennis fracture.” It is the most common type of proximal fifth metatarsal fracture. The mechanism of this fracture pattern remains controversial; it may be caused by a violent contracture of the peroneus brevis muscle during sudden inversion or by avulsion by the lateral band of the plantar fascia.
Jones fracture mechanism of injury is an adduction force applied to the foot while the ankle joint is plantar flexed. Jones fracture occurs in a vascular watershed area, which is at a higher risk for nonunion than the zone 1 fracture. A Jones fracture has a higher incidence in the athletic (ie, football or basketball) or active population. It generally presents acutely in nature and has a nondisplaced fracture pattern.
Diaphyseal fifth metatarsal fractures are most commonly stress induced. The mechanism of injury is from repeated distractive forces, increase in activity, or extensive sports practice. Both structural and biomechanical abnormalities can lead to the repetitive load concentrations. Diaphyseal stress fractures also have an increased risk of nonunion due to a close proximity to the watershed area of the fifth metatarsal. A higher incidence of stress fractures can be seen in patients with pes cavus, metatarsus adductus, Charcot foot, and Charcot-Marie-Tooth disease.