Unusual associated postero-medial process of the talus fracture with medial malleolus and cuboid

1. Introduction 

The fracture of the postero-medial process of the talus is very rare. It is caused by the avulsion of the posterior talo-tibial ligament. The diagnosis is usually missed in favor of distortion of the ankle. Treatment depends on the fragment's dimensions and its displacement.

2. Observation 

A 16-year-old girl fell from a height of 5m and sustained trauma to the right ankle and other injuries. The patient suffered from pains and swelling. The inspectionshowed ecchymosis under the lateral malleolus, the palpation revealed pain in sub-malleolar side. The X-rays showed a displaced postero-medial process fracture of the talus, associated with undisplaced medial malleolar and cuboid fractures (Fig. 1). The CT-scan confirmed the postero-medial fracture with 3mm displacement (Fig. 2). Under anesthesia, the ligament testing showed lateral laxity III c. Open reduction and internal fixation using 3.5 cortical screw was performed through a postero-medial approach (Fig. 3). The medial malleolus and cuboid did not require either reduction or fixation. After 6 weeks of immobilization (Fig. 4), followed by functional rehabilitation, a good result was achieved. The ankle is now pain free, stable with good motion. This was expressed as 15° dorsal flexion, 10° plantar flexion, 10° inversion and 5° for eversion.

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Fig. 1. Pre-operative X-rays showing a displaced postero-medial fracture of the talus, with medial malleolus and cuboid fracture.

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Fig. 2. CT-scans of ankle.

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Fig. 3. X-rays showing fixation of the postero-medial process using the 3.5 screw.

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Fig. 4. X-ray after consolidation.

3. Discussion 

The fracture of the postero-medial process of the talus is extremely rare. Only one case in immature bone is reported in the literature [1]. The most frequent configuration runs through the neck [2]. The association with fracture of the medial malleolus and cuboid has never been reported. This raised questions about the mechanism of injury. Initially the indirect mechanism was considered by the avulsion of the posterior talo-tibial ligament which follows a movement by pronation and dorsiflexion [2], [3], [4]. A pure pronation causes direct trauma which is associated with fracture of the sustentaculum tali and the lateral malleolus [5]. In our case, the medial malleolus fracture associated with comminuted fracture of the postero-medial tubercle indicated predominant inversion. This lesion suggests an impingement with medial malleolus. The inversion is supported by the presence of lateral ligament rupture and cuboid avulsion by the peroneal longus tendon. Conservative treatment has yielded positive results [5]. Nevertheless, successful anatomic and functional results were reported using surgical treatment [1], [6]. Continuing pain has led to resection of small fragments [2], [3], [7]. The only solution of our comminuted fracture consisted of an open reduction and internal fixation. The postero-medial approach was used [1], [8] for controlling the reduction and osteosynthesis. This was done to ensure restoration of joint integrity [9].

According to all reported cases in the literature, we can classify these fractures as the type 1. These consist of partial postero-medial tubercle fractures containing the subtalar joint which could be undisplaced or displaced. We would also classify the total postero-medial fracture as type 2; these may be undisplaced, displaced or comminuted.

This classification system can clarify the treatment methods. Open reduction and internal fixation are logically indicated in displaced and comminuted fracture.