Foot and Ankle cases 43
A 28-year-old man falls from a ladder at work from approximately 12 feet, injuring his right ankle. He is taken by ambulance to the emergency room where radiographs of the right ankle are obtained (Fig. 5–89). A closed reduction is attempted in the emergency room.
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Figure 5–89 A: Lateral ankle radiograph. B: AP ankle radiograph.
What is the most likely structure to block a successful closed reduction of the joint?
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Extensor digitorum brevis muscle
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Posterior tibial tendon
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Peroneal tendons
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Flexor hallucis longus tendon
Discussion
The correct answer is (B). This patient has sustained a closed lateral subtalar dislocation. The vast majority of subtalar dislocations (85%) occur when the calcaneus and remaining foot displace medially, and the talar head is left prominent dorsolaterally. The talar head may even buttonhole through the extensor digitorum brevis muscle/tendon unit leaving that structure and the capsule of the talonavicular joint to interpose between the talus and navicular blocking a successful attempt at closed reduction. The lateral subtalar dislocation is more likely to have the reduction attempt blocked by an interposed posterior tibial tendon or flexor digitorum longus tendon.
The joint is successfully reduced and splinted in the ER and the patient is now comfortable, without any signs of compartment syndrome or open wounds.
What is the most appropriate next step in treatment?
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Measurement of ankle brachial index (ABI)
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Referral for ligament reconstruction
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Referral to physical therapy
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CT scan of the ankle
Discussion
The correct answer is (D). A postreduction CT scan (Fig. 5–90) is recommended to evaluate for congruency of the joints, incarcerated bone fragments in the subtalar and talonavicular joints, and associated fractures. Vascular compromise is not a frequent complication in subtalar dislocation, and the ABI is measured above the most significant zone of injury. The ligaments about the subtalar joint are significantly injured in a subtalar dislocation, but stiffness, rather than instability, is a more common sequela of the injury. The patient will likely benefit from therapy to
combat stiffness, but the postreduction CT scan is more appropriate in the acute setting.
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Figure 5–90 A: Sagittal CT reconstruction of the ankle after reduction showing fracture of the lateral process of the talus with fragmentation. B: Coronal CT reconstruction of the ankle after reduction.
Objectives: Did you learn...?
Describe which structures often block reduction of a subtalar dislocation? Discuss the importance of a CT scan after reduction?