Mechanism of Injury:
Fractures of the ankle can result from low-or high-energy forces. Fractures due to low-energy forces may be caused by one of the following mechanisms:
1. Rotational stresses to the ankle caused by twisting forces at the ankle joint while walking, running etc. This is the most common mode of injury.
2. Axial stress on the ankle joint results in fracture involving tibial plafond
(i) The position of the foot at the time of injury
(ii) The deforming force.
The position of the foot at the time of injury can be supination or pronation and is described first. The deforming force, which can be adduction, abduction, external rotation and vertical loading; is described next. Twisting force produces external rotation. Fall to one side produces adduction or abduction injury. The four most common deforming forces are: supination/external rotation, pronation/external rotation, supination/adduction and pronation/abduction.
Classifications of Ankle Fractures
Lauge-Hansen classified the ankle fractures based on the pathogenesis or the deforming force (i.e. the mechanism of injury). This classification helps in the manipulative reduction of the fracture, if the displacement is understood correctly. The first part of the classification specifies the position of foot during injury and second part of the title specifies the deforming force, for example:
1. Supination-external rotation injury (most common mechanism of injury)
2. Supination-adduction injury
3. Pronation-external rotation injury
4. Pronation-abduction injury
5. Vertical-compression injuries.
However, there is another classification by Danis and Weber which is relatively simple.
Modified Danis-Weber classification: This is based upon the level of fibular fracture and is purely a radiological classification. In this classification, the fibula is considered as the key to the ankle stability. The higher the fibular fracture, the more extensive is the damage to the tibiofibular ligaments and thus greater the instability of the ankle mortise.
Type A: Fibular fractures below the level of inferior tibiofibular syndesmosis
Fibula: Transverse avulsion fracture at or below the level of ankle joint: or rupture of the lateral ligament complex.
Medial malleolus: Intact or sheared, with almost a vertical fracture.
Posterior malleolus: As a rule intact.
Syndesmosis (Tibiofibular ligament complex): Always intact.
Type B: Fractures at the level of inferior tibiofibular fibular syndesmosis.
Fibula: Oblique fracture of the fibula at the level of the ankle joint.
Medial malleolus: Avulsion fracture (fracture line horizontal) or rupture of the deltoid ligament.
Posterior malleolus: Either intact or sheared off as a posterior lateral fragment.
Syndesmosis: Usually, intact or partial rupture.
Type C: Suprasyndesmotic fibular fractures unstable injury.
Fibula: Shaft fracture anywhere between the syndesmosis and the head of fibula.
Medial malleolus: Avulsion fracture or rupture of the deltoid ligament.
Posterior malleolus: Either intact or pulled off.
Syndesmosis: Always disrupted.
The patient typically present s with a twisting injury to the foot following which they com plain of inability to bear weight, pain around the ankle and very often swelling around the ankle. Clinically the stability of the ankle joint must be tested by valgus and varus stress under anesthesia. Associated injury to the tendons and the neurovascular bundles, which run in close vicinity to the joint, has to be ruled out. The state of the skin must be checked. The skin over the deformed ankle may get unduly stretched, resulting into necrosis, if not reduced immediately.
Antero posterior, lateral and mortise view must be taken to define the exact fracture pattern.
The ankle fractures must be reduced accurately. Since ankle is a major weight joint, any incongruity of the articular surface, or tilt or disruption of the ankle mortise can lead to early osteoarthritis. The aim of the treatment in ankle fractures therefore is:
1. Anatomical positioning of the talus.
2. To obtain a smooth articular alignment of the ankle mortise.
For management and prognosis, ankle fractures may be grouped into stable and unstable fractures, depending upon the position and the talus, and its instability on light stress. This classification is of importance in treatment and prognosis.
Conservative treatment is suggested in treating stable fractures viz. isolated fibular fractures without a medial side injury. These fractures can be treated by below-knee plaster casts for 4-6 weeks followed by graduated weight bearing In unstable fractures with displaced talus closed reduction is achieved by manipulating talus under anesthesia and protecting it with above knee plaster cast for 4-6 weeks.
Open reduction and fixation: This is advocated in unstable injuries and in those injuries where the ankle joint is not properly aligned.
Internal fixation is achieved by
1. Tension band wiring
2. Malleola screws
3. Plate and screw fixation for lateral malleolus.
Major injuries of the ankle may be associated with the following complications:
1. Non union: Neglected fracture of the medial malleolus may go into nonunion. In old injuries reduction of the fracture and the ankle mortise may be difficult impossible.
3. Osteoarthritis: If the fracture has not been treated properly leading to incongruity of the articular surface, early osteoarthritis may set in. The patient has chronic pain and swelling of the ankle necessitating ankle arthrodesis.