ESSENTIALS OF DIAGNOSIS
Pain to the lateral border of the foot.
Swelling and ecchymosis to the later aspect of the foot.
Difficulty with weight bearing.
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 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; and (zone 3) diaphyseal stress.
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 acute 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.
All fifth metatarsal fractures present with pain to the lateral border of the forefoot and difficulty with weight bearing. If the fracture is acute, there is associated swelling and ecchymosis.
The symptoms of stress fracture differ from that of a Jones fracture. Stress fracture displays a prodromal symptom of pain that is associated with activity.
Plain radiographs should be obtained to diagnose a fifth metatarsal fracture including anteroposterior, lateral, and oblique foot images.
Zone 1 fracture pattern is extra-articular and involves the tuberosity or styloid process. This fracture pattern is often associated with a lateral ankle sprain. Therefore, the Ottowa rules should be followed, which include obtaining radiographs in patients with ankle inversion injuries who have associated midfoot pain and bony tenderness to the navicular and the base of the fifth metatarsal as well as those who are unable to bear weight.
Zone 2 is a transverse fracture that is located at the diaphyseal-metaphyseal junction approximately 1.5 cm from the tuberosity. It usually involves the fourth and fifth intermetatarsal articular facet.
Zone 3 fracture is located in the proximal diaphysis of the fifth metatarsal and distal to the fourth to fifth metatarsal articulation. However, plain radiographs may not show a fracture early in the process; the fracture may not be evident for up to 3 months. Other imaging modalities, such as MRI and bone scan, can help with earlier detection of a stress fracture.
There is considerable variability in the literature concerning the optimal treatment of fifth metatarsal fractures. Blood supply plays an important role in the healing ability of fifth metatarsal fractures. Perfusion to the fifth metatarsal comes from the metaphyseal arteries at the base of the metatarsal. A nutrient artery also enters at the proximal diaphysis and crosses the watershed area. The watershed area is at the metaphyseal-diaphyseal junction. Most fifth metatarsal fractures that occur outside of the watershed region tend to heal with immobilization or protected weight bearing.
Nondisplaced and minimally displaced distal fifth metatarsal fractures can be treated with weight-bearing immobilization (short leg cast versus boot) for 4–6 weeks.
Treatment for nondisplaced zone 1 fracture consists of a stiff-soled shoe or weight-bearing immobilization (short leg cast versus boot) for 6–8 weeks. Small displaced symptomatic tuberosity fracture fragments may require excision. Larger displaced or intra-articular fractures that are greater than 30% of the articular surface or with an articular step off of 2 mm can be considered for surgical fixation.
Treatment for acute nondisplaced zone 2 fracture is non–weight-bearing immobilization for 6–8 weeks. Prolonged duration of immobilization up to 12 weeks may be required if tenderness persists. For higher performance athletes or in symptomatic fracture patterns with nonunion/sclerosis surgical management should be considered.
Treatment for zone 3 acute nondisplaced fractures is non–weight-bearing immobilization for 6–8 weeks. Prolonged duration of immobilization up to 12 weeks or more may be required if tenderness persists. For higher performance athletes or in symptomatic fracture patterns with nonunion/sclerosis, surgical management can be considered. Early surgical fixation of acute Jones fractures result in shorter times to union, lower incidence of refracture, and return to athletics compared with conservative treatment.
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