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•the medial joint space must be restored to its normal width, i.e. the same width as the tibiotalar space (about 4 mm)

•oblique X-rays must show that there is no tibiofibular diastasis.

Ankle fractures are often unstable. Whatever the method of reduction and fixation, the position must be checked by X-ray during the period of healing.

UNDISPLACED FRACTURES

The first step is to decide whether the injury is stable or unstable (Figure 32.6).

Isolated undisplaced Danis–Weber type A fractures These fractures are stable and will need minimal splintage: a firm bandage or stirrup brace is applied mainly for comfort until the fracture heals.

Undisplaced type B fractures These are potentially unstable only if the tibiofibular ligament is torn or avulsed, or if there is a significant medial-sided injury. X-rays will show if the syndesmosis or mortise is intact; if it is, a below-knee cast is applied with the ankle in the neutral (anatomical) position. The plaster may need to be split and, if so, it must be completed or replaced when swelling has subsided. A check X-ray is taken at 2 weeks to confirm that the fracture remains undisplaced. An overboot is fitted and the patient is taught to walk correctly as soon as possible. The cast can usually be discarded after 6–8 weeks. Ankle and foot movements are regained by active exercises when the plaster is removed. As with any lower limb fracture, the leg must not be allowed to dangle idly – it must be exercised and elevated.

accompanied by disruption of the medial joint structures as well as the tibiofibular syndesmosis and interosseous membrane. These defects may become apparent only when the fracture displaces in a cast; arguably, therefore, type C fractures are better fixed from the outset.

DISPLACED FRACTURES

Reduction of these joint disruptions is a prerequisite to all further treatment; knowledge of the causal mechanism (and this is where the Lauge-Hansen classification is useful) helps to guide the method of closed reduction. Although internal fixation is usually performed to stabilize the reduction, not all such fractures require surgery.

Displaced Danis-Weber type A fractures The medial malleolar fracture is nearly vertical and after closed reduction it often remains unstable; internal fixation of the malleolar fragment with one or two screws directed almost parallel to the ankle joint is advisable. A perfect reduction should be aimed for, with accurate restoration of the tibial articular surface. Loose bone fragments are removed. The lateral malleolar fracture, unless it is already perfectly reduced and stable, should be fixed with a plate and screws or tension-band wiring (Figure 32.7). Postoperatively a ‘walking cast’ or removable splintage boot is applied for 6 weeks; the advantage of removable splintage is that early physiotherapy can be commenced.

Displaced Danis-Weber type B fractures The most common fracture pattern is a spiral fracture of the fibula and an oblique fracture of the medial malleolus. The causal mechanism is external rotation of the ankle when the foot is caught in a supinated position.

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Incomplete reduction Incomplete reduction is common and, unless the talus fits the mortise accurately, degenerative changes may occur. This can sometimes be prevented by a corrective osteotomy.

Non-union The medial malleolus occasionally fails to unite because a flap of periosteum or other tissue is interposed between it and the tibia. It should be prevented by operative reduction and screw fixation.

Joint stiffness Swelling and stiffness of the ankle are usually the result of the soft-tissue injury. Optimal treatment can help to mitigate these potential problems. The patient must walk correctly in plaster and, when the plaster is removed, he or she must, until circulatory control is regained, wear a support bandage and elevate the leg whenever it is not being used actively. Physiotherapy is always helpful.

Complex regional pain syndrome (CRPS) This often follows fractures of the ankle. The patient complains of pain in the foot; there may be swelling and diffuse tenderness, with gradual development of trophic changes and severe osteoporosis. Management is discussed in Chapter 10.

Osteoarthritis Malunion and/or incomplete reduction may lead to secondary osteoarthritis of the ankle in later years. Unless the ankle is unstable, symptoms can often be managed by judicious analgesic treatment and the use of firm, comfortable footwear. However, in the longer term, if symptoms become severe, arthrodesis may be necessary.

PILON FRACTURES

Unlike the twisting injuries that cause the common ankle fractures, pilon injury to the ankle joint occurs when a large force drives the talus upwards against the tibial plafond, like a pestle (pilon) being struck into a mortar. There is considerable damage to the articular cartilage and the subchondral bone may be broken into several pieces; in severe cases, the comminution extends some way up the shaft of the tibia.

Clinical features

There may be little swelling initially but this rapidly changes and fracture blisters are common. The ankle may be deformed or even dislocated; prompt approximate reduction is mandatory.

Imaging

This is a comminuted fracture of the distal end of the tibia, extending into the ankle joint. The fracture may be classified according to the amount of displacement and comminution, but in all cases assessment is far better

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Figure 32.11 Same case as Figure 32.10 – outcome At 3 months after minimal approach reduction and fixation with distal locking plates the fractures have healed and the joint is congruent and normally aligned.

however, a challenging problem with poor functional results in these complex fractures, which represent a significant soft tissue injury as well as bony jigsaw. Although bony union may be achieved, the fate of the joint is decided by the degree of cartilage injury – the ‘invisible’ factor on X-rays. Secondary osteoarthritis, stiffness and pain are still frequent late complications in these injuries.

ANKLE FRACTURES IN CHILDREN

Mechanism of injury

The foot is fixed to the ground or trapped in a crevice and the leg twists to one or the other side. The tibial (or fibular) physis is wrenched apart, usually resulting in a Salter–Harris type 1 or 2 fracture. With severe external rotation or abduction the fibula may also fracture more proximally. The tibial metaphyseal spike may come off posteriorly, laterally or posteromedially; its position is determined by the mechanism of injury and suggests the method of reduction. With adduction injuries the tip of the fibula may be avulsed.

Type 3 and 4 fractures are uncommon. They are due to a supination–adduction force. The epiphysis is split vertically and one piece of the epiphysis (usually the medial part) may be displaced.

Two unusual injuries of the growing ankle are the Tillaux fracture and the notorious triplane fracture. The Tillaux fracture is an avulsion of a fragment of tibia by the anterior tibiofibular ligament (Figure 32.13); in the child or adolescent this fragment is the lateral part of the epiphysis and the injury is therefore a Salter–Harris type 3 fracture.

The triplane fracture occurs on the medial side of the tibia and is a combination of Salter–Harris type 2 and 3 injuries. Fracture lines appear in the coronal, sagittal and transverse planes. Injury to the physis may result in either asymmetrical growth or arrested growth.

Clinical features

Following a sprain the ankle is painful, swollen, bruised and acutely tender. There may be an obvious deformity, but sometimes the injury looks deceptively mild.

Imaging

Physeal injuries are quite common in children and almost a third of these occur around the ankle (Figure 32.12).

Undisplaced physeal fractures – especially those in the distal fibula – are easily missed. Even a hint of physeal widening should be regarded with great suspicion and

Figure 32.13 Tillaux fracture Diagram illustrating the elements of this unusual injury.

the child X-rayed again after 1 week. In an infant the state of the physis can sometimes only be guessed at, but a few weeks after injury there may be extensive periosteal new bone formation.

In triplane fractures the tibial epiphysis may be split in one plane and the metaphysis in another, thus

Figure 32.14 Ankle fractures in children (a) Salter– Harris type 2 injury; after reduction (b) growth has proceeded normally. (c) Salter–Harris type 3 injury;

(d) the medial side of the physis has fused prematurely, resulting in distorted growth.

making it difficult to see both fractures in the same X-ray. CT scans are particularly helpful in these and other type 3 injuries.

Treatment

Salter–Harris types 1 and 2 injuries are treated closed. If it is displaced, the fracture is gently reduced under general anaesthesia; the limb is immobilized in a full length cast for 3 weeks and then in a below-knee walking cast for a further 3 weeks. Occasionally, surgery is needed to extract a periosteal flap, which prevents an adequate reduction (Figure 32.14).

Type 3 or 4 fractures, if undisplaced, can be treated in the same manner, but the ankle must be re-X-rayed after 5 days to ensure that the fragments have not slipped. Displaced fractures can sometimes be reduced closed by reversing the forces that produced the injury. However, unless reduction is near-perfect, the fracture should be reduced open and fixed with interfragmentary screws, which are inserted parallel to the physis. Postoperatively the leg is immobilized in a below-knee cast for 6 weeks.

Tillaux fractures are treated in the same way as type 3 fractures (Figure 32.15). Triplane fractures, if undisplaced, can be managed closed but require vigilant monitoring for late displacement (Figure 32.16). Displaced fractures must be reduced and fixed.

Complications

Malunion Imperfect reduction may result in angular deformity of the ankle – usually valgus. In children under 10 years old, mild deformities may be accommodated by further growth and modelling. In older children the deformity should be corrected by a supramalleolar closing-wedge osteotomy.

Asymmetrical growth Fractures through the epiphysis (Salter–Harris type 3 or 4) may result in localized fusion of the physis. The bony bridge is usually in the

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medial half of the growth plate; the lateral half goes on growing and the distal tibia gradually veers into varus. MRI and CT are helpful in showing precisely where physeal arrest has occurred. If the bony bridge is small (less than 30% of the physeal width), it can be excised and replaced by a pad of fat in the hope that physeal growth may be restored. If more than half of the physis is involved, or the child is near the end of the growth period, a supramalleolar closing-wedge osteotomy is indicated.

Shortening Early physeal closure occurs in about 2% of children with distal tibial injuries. Fortunately, the resulting limb length discrepancy is usually mild. If it promises to be more than 2 cm and the child is young enough, proximal tibial epiphysiodesis in the opposite limb may restore equality. If the discrepancy is marked, or the child near the end of the growth period, leg lengthening is indicated.

PRINCIPLES IN MANAGING INJURIES

OF THE FOOT

Injuries of the foot are apt to be followed by residual symptoms and loss of function that seem out of proportion to the initial trauma. Severe injuries affect the foot as a whole, whatever the particular bone that might be fractured. A global approach is therefore essential in dealing with these injuries, the objective being a return to full weight-bearing without pain, with an appropriate propulsive gait.

Identification of these injuries is particularly challenging in the patient with multiple trauma, where the more subtle foot injuries might be missed as the life-threatening truncal injuries and limb-threatening long bone injuries distract attention from the more subtle injuries to the foot, which may nonetheless impair eventual function.

Clinical assessment

Figure 32.16 Triplane fracture The three fracture planes may not be seen in a single X-ray, but can be visualized from a combination of images (a,b). In this case the epiphyseal fracture is clearly seen only in the coronal plane CT scan (c).

to one spot. Multiple fractures, or combinations of fractures and dislocations, are easily missed. The circulation and nerve supply must be carefully assessed; a well-reduced fracture is a useless achievement if the foot becomes ischaemic or insensate. Similarly, attention must be paid to the soft tissues and functional movement of the foot; the stiff, painful foot is impaired for propulsion, and maybe even for stance.

Fractures and dislocations may cause tenting of the skin; this is always a bad sign because there is a risk of skin necrosis if reduction is delayed.

Imaging

Imaging routinely begins with anteroposterior, lateral and oblique X-rays of the foot. If a fracture of the talus or calcaneum or fracture-dislocation of the midtarsal joints is suspected, a CT scan of the foot should be obtained.

CT is especially useful for evaluating fractures of the calcaneum, and MRI is helpful in diagnosing osteochondral fractures of the talus. Familiarity with the talocalcaneal anatomy is essential if fractures of the hindfoot are to be diagnosed properly (Figure 32.17).

Body

Figure 32.17 Talus and calcaneum The main features of these two bones, and their relationship to each other, are shown here.

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to diagnose on plain X-ray examination; the deformity is best visualized by 3D CT reconstruction.

Fractures of the lateral and posterior processes These are usually associated with ankle ligament strains. It is sometimes difficult to distinguish between a fracture of the posterior process and a normal os trigonum. A simple rule is, ‘If it’s not causing symptoms, it doesn’t really matter.’

Osteochondral fractures Osteochondral fractures following acute trauma usually occur on the lateral part of the dome of the talus. The diagnosis is often missed when the patient is first seen and may come to light only after CT or MRI scan.

tight, reduction becomes urgent because of the risk of skin necrosis (Figure 32.19). Reduction must be perfect: (1) in order to ensure that the subtalar joint is mechanically sound; and (2) to lessen the chance – or at any rate lessen the effects – of avascular necrosis.

With type II fractures, closed manipulation under general anaesthesia can be tried first. Traction is

(c) (d)

Figure 32.19 Fractures of the talus – treatment

(a) This displaced fracture of the body was reduced and fixed with a countersunk screw (b), giving a perfect radiological result. Fractures of the neck, even if well reduced (c) are still at risk of developing ischaemic necrosis (d). The stabilization with K-wires would probably now be improved upon by using definitive screw fixation, but the risk of avascular necrosis would be the same.