Fractures And Injuries Of The Ankle

Fractures and Injuries of the Ankle

Reference: Geissler, Tsao, Hughes, in Rockwood & Green, Chapter 31. 1996

Main Message – a review of ankle fracture concepts

Points of Interest

Fractures of the Ankle

Anatomy

– there is no articular surface between the distal tibia and fibula, even though there is a small amount of motion between these two bones
– the talus has a curved head, an intermediate neck, and a large tapezoidal body; the body is almost entirely covered by articular cartilage. The dome is trapezoidal, and its anterior surface is wider than the posterior surface by about 2.5 mm. Hence, the talus is more securely locked into the mortise in DORSIFLEXION.
– Syndesmotic Complex: anterior talofibular ligament, posterior talofibular ligament, interosseous ligament, transverse tibiofibular ligament (?!). The anterior talofibular ligament comes off the Tubercle of Chaput (antero-inferior aspect of the tibia). Avulsions of this cause Tillaux (peds) or tubercle of Chaput fractures, or if pulls off the anterior tubercle of the fibula, cause a Lefort/Wagstaffe fracture
– Medial Ligament Complex – 4 parts: superficial and deep deltoid ligament. The superficial is made of 3 portions in a fan-like distribution: tibionavicular, tibiocalcaneal, posterior tibiotalar. The tibionavicular ligament suspends the spring ligament (plantar calcaneonavicular ligament) and holds the talar head from inverting. The deep ligament is a tibiotalar ligament that inserts into the entire nonarticular surface of the medial talus.
– Lateral Ligament Complex – 3 parts: anterior talofibular ligament, posterior talofibular ligament, and calcaneo-fibular ligament (this is not really an ankle stabilizer, as it is lax in weightbearing stance. It really is more of a subtalar stabilizer). The anterior talofibular is weaker than the posterior, which is the strongest of the lateral ligaments and prevents posterior and rotatory subluxation of the talus. The anterior talofibular ligament prevents anterior subluxation when the ankle is plantaflexed.
– the anterior neurovascular bundle passes between tib ant and EHL – therefore, anterior surgical exposures can go either lateral to EHL between EHL and Ext. Dig, mobilizing EHL and the bundle medially, or they can go medial to tib ant and pull tib ant with the bundle laterally.

Biomechanics

– at least 10o of dorsiflexion and 20o of plantarflexion are needed for normal ankle function during gait.
– in sectioning studies, if the syndesmosis and fibula are disrupted, the talus can shift despite the stability of the medial side. Securing the fibula in anatomic position is essential!

Mechanisms of Injury

Lauge Hanson Classification

– Supination/Adduction – leads to a transverse fracture of the lateral malleolus, vertical fracture of the medial (or medial dome impaction)
– Supination/External Rotation – leads to an anterior tibiofibular ligament injury FIRST, then spiral fracture of the fibula, then continuation posteriorly to posterior ligaments or malleolus, then on to the medial side.
– Pronation/Abduction – leads to transverse fracture of the medial malleolus, then syndesmotic injury, then short oblique lateral malleolar fracture
– Pronation/External Rotation – leads to a medial malleolar fracture FIRST, then syndesmotic injur, then spiral fibular fracture, then posterior malleolar or ligament injury

AO Classification

– A – infrasyndesmotic (1 – isolated, 2 – with medial injury, 3 – with posteromedial injury)
– B – trans-syndesmotic (1 – isolated, 2 – with medial injury, 3 – with posterolateral injury)
– C – supra-syndesmotic (1 – simple, 2 – complex, 3 – Maissoneuve (proximal))

X-rays

Talar tilt – the talus and mortise should be parallel – up to 5o of tilt is normal in stress views.
Tibiofibular clear space – the distance between the groove formed by the anterior and posterior tubercles of the tibia and the fibula – should be less than 5 mm.
Talocrural angle – between distal tibia and intermalleolar line – 8-15o.

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