injuries around the ankle

Minor injuries around the ankle must be one of the com­monest presenting conditions in a casualty department. Most of these are minor sprains which only require RICE (Rest, Ice, Compression, Elevation). Nonsteroidal anti-inflammatory drugs may help the pain, reduce swelling and speed rehabilitation. A simple sprained ankle is usually the result of a patient going over on their ankle (an inversion and internal rotation of the foot on the tibia). On examination tenderness is confined, to the lateral side of the ankle and is localised over the ligament. The bone itself is not tender. More serious injuries to the ankle have a pattern characterised by the way in which the injury occurred. The injuries caused by inver­sion and external rotation of the foot on the tibia occur in a sequence. First, the posterior part of the distal fibula fractures off (Fig. 23.41). If the injury is more serious then the foot continues to rotate and the medial collateral ligament fails or the tip of the medial malleolus is pulled off. At this stage the ankle becomes unstable. Finally, if the force continues further, the posterior capsule fails by ripping off the posterior malleolus of the tibia, completely disrupting the ankle joint (see Fig. 23.42).

If the deforming force on the foot is pure inversion then it is usual for the lateral structures to fail first. There is either a rupture of the lateral ligament or avulsion of the tip of the fibula. If, however, only the ligament is ruptured the X-ray may look normal as there will be no fracture visible and the ankle at rest will lie in its normal anatomical position. If the ankle is stressed while the X-ray is taken, by holding the foot inverted using lead-protective gloves, the full extent of the injury will be immediately apparent on the X-ray (see Fig. 23.43). If the injury is more serious, and especially if there is a medial compression element to the fracture, then a vertical shear fracture may develop separating off the medial malleolus (see Fig. 23.44). Some of the standard forms of fracture pattern are shown in (Fig. 23.45).

Value of the history

The history may be helpful in defining what type of ankle injury is likely. Remember that the fracture may have occurr­ed because the ankle was held stationary while the body continued to move. The patient’s description of the injury may need translating into the actual movements of the foot on the tibia and fibula.

Examination

The neurovascular status of the foot should always be tested first. In an ankle dislocation, the circulation to the foot may be compromised, as is the viability of the skin over the extruded talus. Reduction of the fracture is an emergency, if skin necrosis is to be avoided (see Fig. 23.46).

Palpation should start at the proximal fibular head. The Maisonneuve-type fracture is an external rotation of the foot on the ankle. The fibula rotates with the talus, avulsing the anterior diastasis but fracturing just below the knee at the fibula neck. The fracture is not normally noticed on an X-ray centred on the ankle, and therefore only clinical examination will reveal the tenderness which warns you to look for this fracture. Careful palpation down the full length of the fibula and on to the lateral collateral ligament will reveal whether there is likely to be a fracture of the fibula or a tear of the liga­ment. Similar palpation of the medial malleolus and deltoid ligament will give information about the medial side of the ankle. It is always worth including the fifth metatarsal head in this examination, as an inversion of the ankle can result in an avulsion fracture of peroneus tertius from the metatarsal head.

Investigation

Two X-ray views of the ankle will be needed. Most fractures are much better seen in one view than another. The posterior malleolar fracture is very difficult to see in the AP X-ray because it is obscured by the talus and the rest of the tibia. The posterior spiral fracture of the fibula is also difficult to see in the AP X-ray as it is hidden by the silhouette of the intact fibula. A very careful check should be made on the AP X-ray to make sure that the talus has not shifted in the mortice (the socket created by the fibula and the medial malleolus). If the joint space between the talus and the medial malleolus is wider than the joint space between the talus and the plafond of the tibia, then the diastasis ligament between the tibia and the fibula is likely to be disrupted or there is an unstable fracture pattern. If this state of affairs is left untreated then early aggressive arthritis of the ankle will result.

Unusual fractures of the ankle

A direct compression force, such as caused by landing on the feet from a height, can drive the talus up into the tibia, destroying the tibial plafond. The principle of management is the same as for any other fracture, reconstruction of a congruent joint surface. However, this can be very difficult to achieve.

Twisting injuries to the ankle in unusual positions such as full plantar flexion may produce a chip fracture of the talus (see Fig. 23.47). These fractures can be difficult to see as they can be very posterior and lie hidden behind the rest of the talus in a normal X-ray. A shoot-through view of the ankle joint in full plantar flexion should reveal the injury.

Footballers who use the front of the foot for kicking a ball can develop a prominent osteophyte on the front of the tibia, which can then fracture. The appearance of the ankle joint even before a fracture has occurred can be quite unusual because of the prominent osteophyte.

Management

If the injury to the ankle joint is stable with the foot plantigrade then the fracture can be treated in a simple plaster. This should be split for the first 24 hours to allow for swelling, but can then be closed. A very careful check should be made that the talus is stable within the mortice. If you are dealing with an unstable fracture pattern, then the plaster will need changing regularly to maintain a close fit as the swelling goes down. Regular checks using X-rays will also be necessary to make sure that displacement has not occurred.

It is important to keep the foot dorsiflexed in plaster, otherwise a fixed flexion deformity of the ankle may develop within a few weeks. If the fracture pattern is stable then weight-bearing can be allowed, but the plaster will need to be reinforced with a foot piece or an external shoe to protect against wear. If the fracture is unstable then weight-bearing must not be allowed. If you feel that the patient is unlikely to understand or co-operate with this instruction, then a simple solution is to incorporate the knee in plaster flexed to 900. This effectively prevents them getting the foot to the ground, and increases the overall stability of the plaster.

If the injury is of such severity that the ankle joint is unstable and cannot be held in a stable configuration with plaster alone, then open reduction and internal fixation must be considered. Avulsion of the medial malleolus can be reduced and held with a lagged screw, while a vertical shear fracture may require lag screws and a buttress plate. The oblique fracture of the fibula is both more difficult to reduce and more difficult to fix and will require a third tubular plate applied anteriorly or posteriorly with lag screws across. Plates applied directly to the lateral side of the fibula are too bulky and prevent closure of the wound.

Timing of surgery

Unstable ankle injuries produce enormous swelling. If sur­gery is attempted when swelling is excessive then it will be impossible to close the wounds at the end of surgery, and a simple closed fracture will be converted into a complex open fracture. Surgery should therefore be undertaken within a few hours of the injury before the swelling has become too great. Otherwise the ankle should be elevated and a pneu­matic splint used, if available, until the swelling has gone down enough for surgery to be possible. A simple test is to see whether the skin over the ankle is slack enough to create a small pucker with pressure between the fingertip and the thumb. If it is not, then it is too tight for surgery and the wound will not close (Fig. 23.48).

Postoperative care

The normal aim of internal fixation is to create a stable skeleton so that full mobilisation can be undertaken. This is unlikely to be achieved in ankle fractures. The purpose of internal fixation is to create a congruent ankle joint so that early arthritis is avoided. The ankle will still need protecting with plaster, and the patient will need to remain nonweight­bearing for at least 2 weeks and then partial weight-bearing until union has occurred. If a removable plaster is used then early active mobilisation of the ankle joint can be started under the supervision of a physiotherapist, so that stiffness is avoided and swelling is brought down as quickly as possible. Once bone union has occurred and ligaments are felt to be healed an intensive programme of physiotherapy is needed to restore full range of movement in the ankle, and to build up proprioception in the ankle joint. This is carried out using a wobble board (a small platform with a half-ball underneath which requires considerable skill to balance on). Patients should only be allowed to return to contact sport once they have regained full control of the ankle joint as otherwise they will simply repeat the injury.

Ruptured tendoachilles

This injury occurs most commonly in the middle aged. It occurs without warning and is often associated with strenuous exercise such as playing a game of squash. The patient describes hearing a sharp crack behind the heel, and may look around to see if she or he has been struck. There is immediate pain and weakness in the ankle. However, the patient may still be able to plantar flex the foot quite forcibly using the flexor digitorum and flexor hallucis longus. The diagnosis is therefore not as easy to make as might first appear. In a true rupture of the tendon there is swelling and tenderness over the tendoachilles about 3 cm above the heel. If it is possible to palpate deeply, a clear step can be felt in the tendoachilles, especially when compared with the other side. Sometimes the swelling is so great and the patient is in so much pain that it is not possible to feel this step. An alternative injury is a tear at the musculotendinous junction of gastrocnemius much higher up in the calf. Here the ten­derness is much less well localised, some 10 cm above the heel and overall the calf is much more swollen. This injury has a completely different treatment and prognosis, and it is therefore important to distinguish between the two. If the patient is laid prone on the examination couch with their feet hanging over the edge, squeezing of the calf produces severe pain in a rupture of the musculotendinous junction, but in a true rupture of the tendoachilles there is little pain but the foot fails to plantar flex on pressure (see Chapter 20 on examination of joints).

Treatment

Treatment of the tear of the musculotendinous junction is immobilisation with the foot in full plantar flexion and non­steroidal anti-inflammatory drugs. As the pain and swelling go down, gentle mobilisation can be started. Healing is quick as there is a good blood supply.

Treatment of the ruptured tendoachilles is a completely different matter. There is a very poor blood supply, and if the ends are not brought into close apposition the tendon will either fail to heal or heal elongated. Either way, there will be

a severe weakness of plantar flexion of the ankle. Non-operative treatment consists of putting the leg in plaster with the foot fully plantar flexed and the knee flexed to 900 initially to bring the tendon ends together. After 2 weeks the plaster is reduced to a below the knee plaster and the patient is allowed to mobilise on crutches. Over the next weeks, serial plasters are applied gradually bringing the foot up to a normal plantar grade position over a period of 6 weeks. The patient is then allowed to mobilise gently, but full activity is not allowed for a minimum of 3 months. There is a significant rate of re-rupture. Healing the second time is even slower and the likeli­hood of a fixed plantar flexion deformity even greater. Surgical treatment can be performed either percutaneously or under direct vision. The tendon ends are sutured together using strong nylon sutures. The stitches are very difficult to insert as the tendon is macerated and stitches tend to cut out unless they are placed very carefully. If the sutures are pulled too tight the tendon tends to bunch up and then it is impossible to close the wound. There is a significant incidence of wound breakdown and some people would question whether wound healing is any faster or the rate of re-rupture any lower in surgical repair compared with nonoperative treatment.