Applied Evidence

Not just a sprain: 4 foot and ankle injuries you may be missing

J Fam Pract. 2012 April;61(4):198-204

Author(s):

Sprained ankle is common—and commonly overdiagnosed by clinicians who fail to consider these subtle fractures and tendon injuries. Here are 4 to keep in mind.

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References

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4. Stiell IG, Greenberg GH, McKnight RD, et al. Decision rules for the use of radiography in acute ankle injuries. JAMA. 1993;269:1127-1132.

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7. Torg JS, Balduini FC, Zelko RR, et al. Fractures of the base of the fifth metatarsal distal to the tuberosity. J Bone Joint Surg Am. 1984;66:209-214.

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10. Pao DG. Avulsion fracture of the base of the fifth metatarsal not seen on conventional radiography of the foot: the need for an additional projection. Am J Roentgenol. 2000;175:549-552.

11. Egol K. Avulsion fractures of the fifth metatarsal base: a prospective outcome study. Foot Ankle Int. 2007;28:581-583.

12. Jones MH, Amendola AS. Navicular stress fractures. Clin Sports Med. 2006;25:151-158.

13. Fitch KD, Blackwell JB, Gilmour WN. Operation for non-union of stress fracture of the tarsal navicular. J Bone Joint Surg Br. 1989;71:105-110.

14. Judd DB, Kim DH. Foot fractures frequently misdiagnosed as ankle sprains. Am Fam Physician. 2002;66:785-794.

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16. Koslowsky TC, Gausepohl T, Mader K, et al. Treatment of displaced proximal fifth metatarsal fractures using a new one-step fixation technique. J Trauma. 2010;68:122-125.

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PRACTICE RECOMMENDATIONS

• 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

Table 1
Ottawa ankle and foot rules^2-4

Ankle
X-rays are required only if the patient has pain near the malleolus and one or more of the following: Bone tenderness along the distal 6 cm of the posterior edge of the tibia or tip of the medial malleolus Bone tenderness along the distal 6 cm of the posterior edge of the fibula or tip of the lateral malleolus Inability to bear weight for 4 steps, both immediately after the injury and in the emergency department
Foot
X-rays are required only if the patient has pain in the midfoot and one or more of the following: Bone tenderness at the base of the fifth metatarsal Bone tenderness at the navicular bone Inability to bear weight for 4 steps, both immediately after the injury and in the emergency department

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

FIGURE 1
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.

FAST TRACK

Consider these 4 injuries in the differential:

fifth metatarsal fracture
navicular fracture
talar dome injury
peroneal tendon injury

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