Ankle fracture

The ankle fracture (Latin - anat. Malleolar fracture ) is a fracture of the ankle ( OSG ). It is the most common fractures of the lower limbs in adults.

• 8.1 Immediate measures
• 8.2 Conservative
• 8.3 Operational 8.3.1 osteosynthesis of the fibula
• 8.3.2 internal fixation of the medial malleolus
• 8.3.3 Stabilization of the joint fork
• 8.3.4 post-treatment

Anatomy

The ankle of the people (there is also a lower ankle [ USG ] below the ankle bone ) consists of the fibula ( fibula ), the shin bone (tibia) and the ankle bone ( talus ). Tight bands keep the cartilage -covered articular ends of the bones in a joint together: The front and rear powerful Syndesmosenband connect calf and shin to ankle joint; the shaft of the fibula and tibia in the lower leg above are connected by the functionally equivalent extensive interosseous ligament ( interosseous membrane ). The fitted into the ankle joint ankle bone is the outer or lateral ligaments ( anterior talofibular ligament, ligament fibulocalcaneare and ligament Posterior talofibular ) and the roughly triangular ligament ( deltoid ligament ) movably but stable. The load transfer of the foot to the lower leg takes place exclusively through the talus and the lower horizontal joint surface of the tibia. The ankle serve only the lateral guidance of the joint. The medial malleolus is an integral part of the broad, lower tibia end, while the outer ankle is the joint side covered with cartilage tip of the fibula.

Because the talus is not a simple, uniform bone roll, but with different inside and outside radii represents a segment of a cylinder, the movement of the ankle joint in flexion and extension is not a mere hinge movement, but a so-called jaw clamp movement.

Functional Anatomy

Despite the individual differences pronounced wedge shape of the talus roll the fork of the upper ankle joint causes the talus in all functional states largely positive manner. Outer and inner ankle show a corresponding convergence of the wedge shape of the articular surfaces. Neither results in a comprehensible extended plantarflexion mobility of the talus in the fork, nor dorsiflexion leads to a more than slight broadening of the outer fork dimensions. They tried to explain such a perfect joint mechanics by a migratory movement axis. The range of motion of the ankle joint can be described for practical use with a hinge axis but not perpendicular intersects the interior ankle: The arc of motion of plantar flexion to dorsiflexion of the ankle bone rotates inward and the fibula in the same direction about its longitudinal axis. This was confirmed by American students who screwed self-experimentation Kirschner wires into the fibula and were able to show the range of motion of rotation in dorsiflexion / Plantarextension by almost 20 °. In addition, the fibula is bent in the strongest Dorsalstellung little laterally and stretched by its lateral and dorsal displacement of the anterior syndesmosis. The various types of information to the joint conclusion in dorsal or plantar flexion resulting from the examination technique by anatomists and pathologists: Here the tests are carried out on unloaded limbs. Lower body burden of the joint conclusion of Malleolenwangen other hand, is considerably narrower, the syndesmoses get a clear bias, and the displacement of the fibula below the hinge movement is reduced, as has been shown in unpublished experiments corpse. Too little attention also find functional aspects of the so-called " rear " or third " malleolus ": the way beyond the talus role cross- dorso -lateral edge of tibia with this engaging, taut posterior syndesmosis as labrum places particularly in plantar flexion substantial contact point of the joint is: The in German-speaking usual term ankle joint so that neither the anatomical nor physiological facts justice. The shape of the ankle area of ​​the tibia and the fibula is therefore called total also aptly known in English as Mortise, in French as Mortaise. Bowl or pan is a functionally correct Eindeutschung.

Mechanism of injury

The fracture of the ankle is always formed over a more or less severe dislocation ( subluxation or dislocation) of the joint, ie a solution of the bones of the joint from its normal hinged connection at break of at least the outer ankle and possible bony and ligamentous associated injuries. Therefore, the injury is, in principle, dislocation fracture ( fracture-dislocation ). For illustration, we have mapped an ankle fracture dislocation in position. In most cases, the fractures due to the elasticity of the soft tissue envelope by itself reducible, or they are repositioned by paramedics or sports coach at the scene, so that such radiographs rarely occur in hospitals. The injury, popularly known as " twisting " means, usually a Pronationstrauma or supination is based (both indirect trauma ). This basic pattern is completed (eg, eversion, adduction ) of the foot by rotating components. The ankle fracture can be caused by rotation of the lower leg against the fixed foot. Frequently addition, the influences of compressions are effective, such as through the crack of a wall. The radiographic fracture pattern can be determined by lye -Hansen a respective typical formation mechanism assign ( = causative classification ).

Diagnostics

The diagnosis requires not only the collection of history (anamnesis ) and clinical ( physical ) examination, a radiographic examination. It is in the A. P. (anterior -posterior ) beam made ​​with 20 ° internal rotation, as well as in the lateral projection. With Oblique angle of 45 ° avulsions can be detected at Syndesmosenansatz of the tibia (French tuberculé de Chaput Tillaux ). If in doubt, always a long recording to exclude a high fibula fracture ( Maisonneuve fracture ) must be made. The invisible on the radiograph ligament injuries are, but discovered in suspected after induction of anesthesia prior to the actual surgery by a held- ray imager investigation.

In skeletal anomalies, and according to old quarries, but especially with involvement of the lower bearing tibial articular surface through the fracture, an additional computed tomography ( digital x-ray film examination) clarity on the fracture pattern. Band damage and cartilage damage, for example, the talus can be studied very accurately with a digital magnetic resonance imaging.

Classification

Currently, the openings for the surgical treatment are preferred anatomically divided by Danis or derived according to Weber, depending on the height of Wade broken leg in relation to the connective tissue connection between the calf and shin ( syndesmosis ). This classification was supported by the International Association for Study of Internal Fixation (AO) included in their classification and further differentiated:

The extent of joint damage increases from A to C. Associated injuries such as medial malleolus fracture and posterior shin fragment ( Volkmann'sches triangle) can increase the amount of joint damage.

This classification applies only to the local position of the calf broken leg. From the assignment can be inferred approximately to the expected concomitant lesion of the fork supporting ligaments of the syndesmotic region and the interosseous membrane.

More rarely, the classification according to liquor -Hansen is applied. This classification is based on the position of the foot and the direction of movement of the Talusrolle time of the accident:

Associated injuries

Accompanying injuries come to basically always present lesion on the outer ankle also medial malleolus fractures and fractures of the species Weber B and C also lesions of the load-bearing lower shin area. Namely, it is on back and forth on the respective Syndesmosenband, so that large yoke voltage at the moment of rupture at the same time load on, for example, the rear ( triangular ) joint edge it is injured in the form of a combined push-off tear-off fraction. This posterolateral tibial edge, the so-called Volkmann's triangle (after Richard von Volkmann, 1872), has prognostic of a severe variation of a Weber B or C break down, because of its construction, a large compression proportion is necessary, the additional causes damage to the cartilage.

Syndesmosenläsion and Volkmann'sches triangle

The instability of the ankle joint is a consequence of the typical fracture mechanism which tilts in principle the anklebone ( talus ) from the fork. If this results in a fracture of the lateral malleolus below the syndesmosis, the fork stability is of course always the same ( Weber A fracture). If, at the fracture origin to a fracture of the fibula ( fibula ) at the level of the syndesmosis, will tear them. Since it ( Weber B fracture ) is an oblique fracture in this type of fracture, tearing the anterior syndesmosis, while the rear ( stable ) remains connected to the fragment and flips open like a door hinge to the fragment to the outside. In Weber C fractures occur by tilting of the talus first to blow up the Syndesmosenregion before the remaining force breaks the fibula.

The damage to the syndesmosis can occur in two variations: either rip both Syndesmosenbänder ( and parts of the interosseous membrane to the level of the fibular fracture ). Much more often, however, tears the front, weaker Syndesmosenband, and the rear ( stable ) is maintained; it rips the band approach the lower shin from a wide area. Contribute to this compression forces in the talus to the distal tibia joint surface. This avulsion fracture with the name Volkmann'sches triangle ( or Volkmann's triangle) is possible with Weber B, and very common in Weber C fractures as well as the cause of a complete fork instability of the ankle joint ( see Fig.)

Forecast

On fracture of the ankle generally determines the extent of articular cartilage damage prognosis. This damage is caused either equal to the accident by the broken ends, the contortion (see above) or by a compression percentage ( of the rear triangle Volkmann's fracture). On the other hand, also a bad position or joint instability after healing of the fracture to increased wear of the articular cartilage. Already about a year after the injury show up at the ankle because of the pronounced stress wear (secondary or post-traumatic arthritis) with pain, swelling and limitation of movement.

Treatment

Emergency measures

In cases of suspected ankle fracture, the leg should be immobilized and slightly raised to avoid additional pain and minimize swelling. When the skin is intact, the ankle should be cooled in order to minimize the swelling continues. An early treatment of the swelling is not only relieves pain, but also allows early surgery, as in severe swelling of the operation usually has to be delayed until the soft tissue swelling has gone down. With an open fracture the wound must be sterile covered to avoid infection and in particular a lengthy bone infection.

A bad position (dislocation ) of the ankle should by healthcare professionals as soon as possible after the administration of pain - and possibly sedatives ( conscious sedation ) are fixed ( reduction ). It is being pulled by the ankle strong uniform train on foot and then ideally immobilized with a vacuum rail. The early reduction in a failed ankle fracture provided is useful to minimize the risk of pressure ulcers on the thin skin over the ankle. If the blood supply was interrupted for walking through the deformity or nerves are pinched, must be the fastest possible reduction in order to avoid permanent damage.

Conservative

Is a prerequisite for a good result an anatomical (ie completely normal ) restoration of bone shape and sturdy joint guidance. Only undisplaced fractures below the syndesmosis ( Weber A fractures) or minimally displaced Weber B fractures should be treated conservatively without surgery by external stabilization ( eg gypsum ). In patients with circulatory disorders, for example, on the basis of age, vascular disease or diabetes mellitus but should also dislocated fractures are either conservative or minimally invasive surgically. The fractures have established and maintained under anesthesia with the repositioning result percutaneously introduced ( through the skin) and the joint drill wires are put in plaster. Open surgery with exposure of the fragments have here the great disadvantage of wound healing disturbances which may significantly impair the clinical outcome and even lead ultimately to amputation of the operated leg.

Operational

Osteosynthesis of the fibula

For all other fractures with displaced bone fragments and in violation of the fork bands usually open surgery with Knochenverschraubung (osteosynthesis ) and strip stabilization is necessary. The simplest and most biomechanically stable supply is provided with at least two to three lag screws, depending on the length of the oblique fracture of the fibula (Fig.). Exclusive Schraubenosteosynthesen are possible only for simple spiral or oblique fractures, comminuted fractures are associated with single screw into larger fragments, which are then stabilized with a plate. In the other case illustrated a lag screw and a 6-Loch-1/3-Rohrplatte as so-called neutralization plate on outer ankle and a tension band came at the inner ankle for use. Both supplies are stable exercise, a cast immobilization may be waived. The patient is allowed to go with light contact load on crutches.

Internal fixation of the medial malleolus

Mostly it is in the inner ankle fracture an avulsion fracture. A conservative treatment is not possible here. Therefore, the inside of the ankle must be exposed over a longitudinal section. In the fracture gap is always the periosteum taken, which hinders anatomical reduction. After pushing aside the periosteum, the fracture can be easily repositioned anatomically. The fragment is fixed with drill wires or drill wire and lag screw (Fig.). Often there is a medial malleolus fragment from several parts which can be fixed by a plurality of wires and possibly also a cerclage. A screw fixation is not possible with such a multi- fragment fractures.

Stabilize the joint yoke

With fork instability with rupture of the syndesmosis the front syndesmosis must be inspected and, if necessary sewn. The rear Volkmann's triangle with the depending rear syndesmosis is a breitbasiges bony fragment of the posterior inferior tibial articular surface. Flat fragments heal spontaneously fixed bony reliable and may be neglected in the treatment of fractures. Larger fragments of more than 10 % of the distal tibia joint surface has to be securely fitted into the anatomical joint. For this they must be surgically set and fixed with one or more screws.

The connection fibula - tibia must be fixed with a screw. The screw has the task of the first stable supplied fibula into the joint to the tibia ( fibular incisura ) fit and adjust there at the correct distance (hence adjusting screw ). A compression effect may not exercise the screw. Therefore, a thread must be pre-cut for implantation into two involved bones ( fibula and tibia). Since the ankle joint but may not be absolutely stable, but only elastic- stable to allow the rotation of the fibula in the ankle joint, the screw is always removed after the expiry of six weeks after band healing.

Follow-up treatment

In those six weeks necessarily the full load of the operated leg with ankle fracture must be avoided in order not to jeopardize the healing of the syndesmosis and prevent the breakage of the screw. The discharge is carried out with crutches. In exercise stable osteosynthesis performed a so-called plantar contact or rolling using crutches is useful. Pending the achievement of full load after about eight weeks thrombosis prophylaxis with heparin must be made. The removal of the incorporated for fracture stabilization osteosynthesis material should be done on the ankle at the earliest after about a year. Simple lag screws can also remain.

Complications

The often very thin skin conditions, along with the carried out by swelling and a bony deformity Bindegewebsschädigung easily lead to pressure necrosis of the skin that occasionally make even the early metal removal necessary. Particularly critical in this respect is the situation in which the joint remains after ( sprain ) Break in contortion position because it gets the skin usually on the fractured medial malleolus under massive stress. Here only the best Grobreposition ( righting ) by longitudinal traction at heel - if necessary also by unskilled persons ( eg sports coach ) - prevent the worst.

In earlier to stress (lack of compliance) a shift or even the outbreak of the osteosynthesis material, resulting in a lack of fracture healing or false joint formation threatens (pseudarthrosis ). Occurs particularly often this complication in elderly patients whose bone due to osteoporosis has no hold for the osteosynthesis material and also have problems in the safe provision of break - relief means crutches because of the higher ages.

Deep wound infections can cause a bone infection ( osteomyelitis) and / or of early osteoarthritis of the ankle massive lead. Often, here is the operative stiffening of the joint, the only possible definitive measure to allow pain- free walking.

The immobilization or unloading of a leg by surgery leads to a significant increase in the risk for the development of deep vein thrombosis. For prophylaxis, daily injections are performed by low molecular weight heparin.

Complications are particularly common. Patients with circulatory disorders (eg, heavy smokers ) or in diabetics This fact must be considered when assessing the need for surgery (ie, the indication ) should be considered urgently. Also on the operative procedure, this risk profile of an impact: Thus the operation to avoid possible Wundrandnekrosen and following wound infections should not be performed in a tourniquet.

Moreover, an insufficient reduction of bone fracture lead to malunion ( malunion ) and painful functional limitations through to post-traumatic osteoarthritis. Already a shortening or displacement (translation ) of the distal lateral malleolus fragment by 2 mm or tilting or rotation by 5 ° lead to a significant change in the biomechanics and the risk of instability and premature osteoarthritis - which is why an exact intraoperative repositioning is necessary. Conventional manner, it takes on an outer ankle fracture to a displacement of the distal fragment to the outside ( lateral), and subsequently tilting the Talusrolle outward ( valgus ). In rare cases, a corrective osteotomy is necessary.

An exact reduction is most likely in a correct radiograph of the ankle (AP with 20 ° internal rotation, called mortise view, according to Weber ) to detect. Here, the joint space is inside, outside and top evenly far, an imaginary boundary line of the ankle joint shows only a small gap ( soft spot ) between the tibia and fibula, but no step formation. The amount of this soft spots located on the inside of the fibula as a smaller mandrel of the front approach Syndesmosis corresponding to the proximal end of the upper ankle joint and the cartilage is displaced at a shorter proximally. In addition, can be normally a circle exactly think in the distal contour of the lateral malleolus tip and the lateral boundary of the processus fibular tali, but not in a shortening of the lateral malleolus. Upon rotation of the lateral malleolus fragment also the congruence between the lateral malleolus and the fibular notch of the tibia is removed in CT.