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A 26-year-old man twisted his left ankle while sliding into home plate during a baseball game.

The ankle swelled immediately. He was able to bear weight, but could walk only two steps without assistance.

On examination, the ankle was moderately swollen and tender. The swelling and tenderness were greater on the medial than the lateral side of the ankle. There was ecchymosis over the medial malleolar area, but no deformity. Plantar and dorsiflexion were limited due to pain. There was no tenderness over the mid-foot (navicular or base of the fifth metatarsal).

Ankle radiographs were obtained (Figure 1).

  • How would you manage this patient’s ankle sprain?

Three radiographic views are included in a standard ankle series: AP and lateral views and a mortise view (AP view with 15° internal rotation).

The mortise view shows the entire mortise joint space between the talar dome and the medial malleolus, tibial plafond and lateral malleolus (Figures 1B and 2). On the AP view, the lateral malleolus overlaps and obscures the lateral joint space (Figure 1A).

Figure 2

Normal mortise view.

The entire mortise joint space should be of uniform width, ≤4 mm (light gray).

The distal tibiofibular joint (dark gray) should be only slightly wider than the mortise joint space, ≤5.5 mm.

The tibiofibular overlap should be >1 mm on the mortise view.

The mortise view is key to assessing the structural integrity of the ankle. The entire mortise joint space adjacent to the talar dome should be of uniform width. The distal tibiofibular joint space should be only slightly wider than the mortise joint space. Tibiofibular overlap should be at least 1 mm on the mortise view (Figure 2). Lack of overlap implies disruption of the distal tibiofibular joint. The distal tibiofibular joint is also referred to as the ankle syndesmosis.

The tibia and fibula are held rigidly together by the distal and proximal tibiofibular joints and the interosseus ligament. Separation of the distal tibiofibular joint, even if slight, must therefore be accompanied by a second injury, usually a fibular fracture. If a fibular fracture is not seen on the ankle radiographs, radiographs of the entire fibula should be obtained because a proximal fibular fracture is likely to be present.

Clinically, all patients with ankle injuries should be examined for tenderness along the length of the fibula, up to the knee. The “squeeze test” (mediolateral compression of the tibia and fibula at the ...

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