• Treat a nondisplaced shaft fracture of the fifth metatarsal conservatively, with 6 to 8 weeks of immobilization with a protective orthosis. B
• Suspect a navicular fracture in patients who describe a gradual onset of vague, dorsal midfoot pain associated with athletic activity. C
• Order magnetic resonance imaging when you suspect osteochondritis dissecans, as radiographs are insensitive for identifying these lesions. C
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
Ankle sprain, one of the more common injuries that primary care physicians evaluate, is usually managed with conservative treatment. Not uncommonly, however, lateral ankle sprain is diagnosed without consideration of a broader differential diagnosis.
Contributing to the problem is the fact that the clinical presentation of some fractures and tendon injuries is similar to that of a routine sprain. In some cases, the mechanism of injury—sprains are usually caused by excessive inversion of the ankle on a plantar-flexed foot—is similar, as well. What’s more, radiographs are often omitted or misinterpreted.
In the pages that follow, we highlight 4 commonly misdiagnosed injuries: fifth metatarsal fractures, navicular fractures, talar dome lesions, and peroneal tendon injuries. These injuries should be included in the differential diagnosis of an acute ankle injury—or a subacute foot or ankle injury that fails to respond as expected. Prompt recognition and appropriate treatment result in optimal outcomes. When foot and ankle fractures and tendon injuries are misdiagnosed (or simply missed) and do not receive adequate treatment, long-term morbidity, including frequent reinjury and disability, may result.1
Are x-rays needed? Turn to the Ottawa rules
Ankle sprains represent a disruption in a ligament supporting a joint, and result in pain, edema, and ecchymosis, and often affect a patient’s ability to bear weight. While uncomplicated sprains generally heal with conservative treatment, other common foot and ankle injuries may require a different approach.
The Ottawa foot and ankle rules are an evidence-based guide to the use of initial radiographs after acute ankle injury (TABLE 1).2-4 Pain—near the malleoli (for the ankle) or in the midfoot—is the key criterion, but x-rays are recommended only if at least one other specified criterion is also met. With a sensitivity of nearly 100%, the rules have been shown to reliably exclude, and diagnose, ankle and midfoot fractures in children >5 years and adults.2,5
|X-rays are required only if the patient has pain near the malleolus and one or more of the following:|
|X-rays are required only if the patient has pain in the midfoot and one or more of the following:|
Fifth metatarsal fractures are easily missed
The mechanism of injury for a fifth metatarsal fracture is often similar to that of a lateral ankle sprain. In addition, isolated ankle radiographs may not adequately evaluate the fifth metatarsal, which increases the risk of misdiagnosis.6
3 types of fifth metatarsal fractures
Fifth metatarsal fractures involve one of the following:
- an avulsion fracture, caused by the pull of the plantar aponeurosis and the peroneus brevis tendon at the tuberosity of the bone
- a Jones fracture, at the base of the fourth and fifth metatarsal (FIGURE 1)
- a shaft fracture, distal to the fifth metatarsal joint in the proximal diaphysis.6-8
Jones fractures heal slowly
This 50-year-old patient presented with pain and swelling in the ankle and lateral foot shortly after an inversion ankle injury. A radiograph (A) taken at that time reveals a Jones fracture. The second radiograph (B) was taken 6 weeks later, after continued immobilization with no weight-bearing. Three months after the injury (C), the patient was clinically asymptomatic.
While avulsion fractures are generally the result of an inversion ankle injury, Jones fractures are usually caused by a large adductive force applied to the forefoot on a plantar-flexed ankle.6 Shaft fractures, also known as diaphyseal stress fractures, are overuse injuries from chronic overload, usually after a sudden increase in running or walking.9