Ankle fracture, Weber B

The most common ankle fracture: a short oblique fracture of the fibula starting at the level of the joint and running from anterior-inferior to posterior-superior. Stability depends on the medial side: if the deltoid ligament or the medial malleolus is broken, the talus shifts out of the mortise.

Mechanism

Supination–external rotation (Lauge-Hansen SER): the foot is fixed and the leg rotates internally.

Clinical findings

• Swelling over both malleoli. Medial tenderness, bruising or a medial malleolar fracture suggests instability.
• Check the skin: fracture-dislocations must be reduced immediately to save the skin.

Imaging

• AP, mortise and lateral of the ankle.
• If the medial side looks intact: weight-bearing (or gravity stress) mortise view. Medial clear space ≤ 4 mm and equal to the superior clear space = stable, treat in a boot.
• CT if a posterior malleolar fragment is seen.

• AP, mortise and lateral views. Measure the medial clear space (> 4–5 mm = deltoid injury). If unclear, a weight-bearing or gravity stress view decides.
• Lateral view: look for a posterior malleolus fragment; CT if it looks large.

Classification

44B1

Isolated lateral malleolus (B1.1) or with deltoid rupture.

44B2

With a medial malleolus fracture (bimalleolar).

44B3

With medial and posterior malleolus (trimalleolar).

Lauge-Hansen SER I–IV

I anterior syndesmosis, II fibula, III posterior malleolus/posterior syndesmosis, IV medial malleolus or deltoid.

Types shown in 3D

44B1

Isolated transsyndesmotic fibula fracture, medial side intact: the mortise is stable. Walking boot; stress view if in doubt.

44B2

With a medial lesion: medial malleolus fracture (bimalleolar) or deltoid rupture. The talus follows the fibula out of the mortise: fix.

44B3

With a medial lesion and a posterolateral fracture of the tibia (posterior malleolus, Volkmann): trimalleolar. The talus can sublux posteriorly; fix large posterior fragments.

Treatment

Stable (isolated, stress-negative)

Walking boot, weight bearing as tolerated for 6 weeks. Repeat X-ray at 1–2 weeks to confirm the mortise.

Unstable (bi-/trimalleolar or deltoid-equivalent)

Open reduction and internal fixation: lag screw plus one-third tubular neutralisation plate (lateral) or posterolateral antiglide plate on the fibula; medial malleolus with two partially threaded cancellous screws or a tension band. Test the syndesmosis intraoperatively (hook/Cotton test) and fix it if unstable. Fix large posterior malleolus fragments.

Aftercare

Protected or early weight bearing depending on bone quality and fixation; diabetic and neuropathic patients need longer protection.

Complications

• Wound problems and infection (diabetes, smokers)
• Malreduction of the fibula (shortening, rotation) or of the syndesmosis
• Post-traumatic arthritis
• Symptomatic hardware