Fractures of the malleoli are common. Court-Brown et al calculated an incidence of 125/100000/year. They occur equally in both sexes, but are commoner in young men and old women. They are increasingly becoming an elderly person’s osteoporotic fracture.
Most ankle fractures are low-energy twisting injuries sustained in falls, and only 1-2% are open injuries.
Anatomy and biomechanics
The ankle is a modified hinge joint between the tibial plafond, medial and lateral malleoli proximally and the talus distally. The inferior tibiofibular and subtalar joints are also intimately related to ankle function. The ankle joint capsule is reinforced by the anterior talofibular (ATFL), calcaneofibular (CFL) and posterior talofibular ligaments (PTFL) laterally, and by the deltoid ligament medially, of which the deep tibiotalar part (DTTL) is the most important for ankle stability. There are also anterior (AITFL), interosseous and posterior ligaments of the inferior tibiofibular joint and a posterior transverse band, the posterior intermalleolar ligament. The subtalar joint is stabilised by the lateral, interosseous and cervical talocalcaneal ligaments, and by the calcaneofibular and superficial deltoid ligaments and the inferior extensor retinaculum, which cross both ankle and subtalar joints.
The ankle dorsiflexes and plantarflexes through an axis that passes through the tips of the malleoli. As the lateral malleolus is longer and more posterior than the medial, the axis is not quite parallel to either the ground or the coronal plane. In addition, the instant axis of rotation of the ankle moves from moment to moment. Hence, as the ankle dorsiflexes, it rotates externally and vice versa. The talus is also wider anteriorly than posteriorly, so the lateral malleolus has to rotate externally by about 11deg in the course of full dorsiflexion. Damage to the syndesmosis may interfere with ankle dorsiflexion or make it painful. The rotation of the ankle (and proximal limb) in relation to a fixed foot an the ground are accommodated by the rotation of the subtalar joint. Stiffness of the subtalar joint interferes with ankle movement and smooth gait.
When weight is borne through the ankle, the talus is compressed up into the bony mortise, and the shape of the bones produces stability. Therefore, it makes no sense to prevent patients weightbearing on the ankle unless there is a significant defect in the tibial plafond.
Without axial loading, the ligaments become more important for stability, especially in plantar flexion. In most ankle fracture patterns, the deep tibiotalar part (DTTL) of the deltoid ligament is the most important structure in determining ankle stability. The biomechanical work of Michelson and others shows that, provided the DTTL remains intact and attached to the tibia, the talus will not displace in the mortise, no matter what happens to the lateral side or the syndesmosis. However, if the DTTL is ruptured, or detached form the tibia by a medial malleolar fracture, the talus is potentially unstable and will tend to follow the fibular displacement. Axial loading (weightbearing!) does not increase talar instability unless there is a significant defect in the tibial plafond, but how large this has to be is not known for certain – probably somewhere between 25-40%.
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Undisplaced AO B ankle fractures. The Xrays look the same, but the soft tissue injuries are different. On the left the PTTL is intact and the ankle is stable. On the left the PTTL is torn and the ankle is potentially unstable - the risk of displacement is about 3% |
Yablon published avery influential paper in 1979, in which he showed that in displaced ankle fractures, "the talus follows the fibula" (though he did not really study stable fractures or examine what determines stability). This led to an emphasis on the fibula as a stabilising buttress, and on stabilising the fibula in fixing ankle fractures. More recent biomechanics, particularly Michelson's work referred to above, strongly suggests that, in fact, the restraining force of the DTTL is more important in most situations; when the DTTL is torn, the fibula becomes more important.
Ankle stability according to Yablon |
Ankle stability according to Michelson |
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The lateral malleolus is seen as a buttress and controls the position of the talus |
The DTTL is seen as a tether which prevents the talus displacing... |
unless the ligament is torn, when the fibula becomes more important |
The contact area of the ankle is basically the whole tibial plafond surface, but it is extended slightly by weightbearing. Axial loading forces are mainly borne by the plafond and amount to 5x body weight in the late stance phase of gait. Tibiotalar incongruity reduces contact area and increases localised loading in the remaining contact area. There is an often-quoted paper (Ramsey and Hamilton ) which showed that 1mm of lateral talar displacement reduced contact area by 40%. However, the methodology was completely unrepresentative of ankle loading in vivo in any fracture configuration. Highly-unstable trimalleolar fracture models, with an effective deltoid ligament division and major talar migration, can reduce contact area and increase loading by up to 40% in vitro.
After an ankle fracture, the biomechanics of the ankle may change in a number of ways:
- loss of range of motion, particularly loss of dorsiflexion, can have a significant effect on gait and increases forefoot loading
- alteration in contact area and loading as a result of inadequate reduction and mortise incongruity can promote post-traumatic arthritis
- alterations in inferior tibiofibular movement could reduce functional ankle dorsiflexion, although this seems to be an uncommon problem in practice
Fracture mechanics and classification
A fracture classification should provide diagnostic information and guidance as to natural history, treatment and expected outcome. It should be simple enough to use in practice and be sufficiently reproducible for datasets created using it to be compared. Studies on fracture classifications at various body sites have shown that these criteria are not often met.
Pathomechanics and classification are brought together in this document because one of the main ankle classification systems (Lauge-Hansen) is based on pathomechanics and the other (Weber/AO) takes into account pathomechanical factors in describing fracture patterns.
Lauge-Hansen (1950) described cadaver experiments in which various forces were applied to specimens and fracture configurations produced. Each configuration was defined by two factors: the position of the foot (pronation or supination) and the force applied to the ankle (adduction, external rotation or abduction), and in addition each configuration had a number of stages describing sequential injuries as the force was applied:
- supination-adduction – transverse lateral malleolar fracture below the tibial plafond and vertical shearing fracture of the medial malleolus
- supination-external rotation – anterior syndesmotic injury, oblique fibular fracture at the level of the plafond, medial malleolar fracture or deltoid avulsion, posterior syndesmotic injury and posterior malleolar fracture
- pronation-external rotation – medial malleolar/deltoid injury, syndesmotic injury, bending fracture of fibula above syndesmosis
- pronation-abduction – medial malleolar/deltoid avulsion, anterior syndesmotic injury, interosseous membrane tear, high fibular fracture
Danis (1949) and subsequently Weber (1972) classified fractures by the radiographic appearance, according to the relationship of the fibular fracture to the syndesmosis:
- type A – fibular fracture below the syndesmosis – corresponds to the Lauge-Hansen supination-adduction fracture
- type B – fibular fracture at the level of the syndesmosis – largely corresponds to the Lauge-Hansen supination-external rotation fracture
- type C – fibular fracture above the syndesmosis – includes the Lauge-Hansen pronation-external rotation and pronation-abduction fractures
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Another type A (fibular avulsion), but with a vertical medial fracture due to adduction - this can be quite unstable and may have impaction of the plafond around the fracture line |
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AO type B, intact medial side - stable |
AO type B, bimalleolar. The talus is displaced laterally about 7mm. The DTTL is detached from the tibia - unstable |
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AO type C, bimalleolar, displaced but no syndesmotic widening |
AO type C, unimalleolar, major syndesmotic diastasis |
This was intended as a guide to the increasing likelihood of surgical treatment. Fracture patterns without a fibular fracture (10%) cannot be classified by this system (Kennedy et al 1998). The AO group used the Weber system as the basis of the malleolar section of the comprehensive fracture classification, providing groups and subgroups to include 27 fracture types, some with qualifiers.
Some practitioners simply describe ankle fractures on the basis of the number of malleoli fractured. While this is somewhat crude and excludes useful information, it is an important prognostic factor.
Several biomechanical studies have attempted to reproduce the work and classification of Lauge-Hansen. Unfortunately, the fractures they produced did not correspond with Lauge-Hansen’s classification. If anything, the fracture patterns produced by a given force in modern experiments tend to be less severe than those described by Lauge-Hansen, and the relationship between forces exerted on the ankle and fracture patterns is not exact.
Studies of the inter-observer and intra-observer reproducibility of both systems have found that reproducibility of both systems is moderate; if anything the Weber system is probably more reproducible, but this advantage may be lost at the group level and the subgroup level has not been tested
Finally, studies relating the fracture configuration to prognosis show that fracture configuration by the Lauge-Hansen and Weber systems is not highly predictive of prognosis; the number of malleoli injured and initial talar displacement are probably more important.
In addition, the Weber B group has been shown to include fractures of very different prognosis, grouping together fractures with both intact and disrupted medial malleolus and deep deltoid ligament; this probably also applies to the A and C groups to some degree. The Weber classification omits isolated fractures of the medial and posterior malleoli, although this is covered by the full AO classification.
The AO system would appear to have the following advantages:
- based on radiographic findings rather than hypothetical fracture mechanisms which have not been substantiated by modern biomechanical studies
- probably more reproducible
Neither system clearly presents the distinctions between injury configurations which are important for treatment; in particular the distinction between stable and unstable injury configurations are buried in the classification subgroups, especially in the AO classification. There is a need to describe fracture patterns, but key treatment decisions are based more on the stability of the fracture than any other factor, and prognosis (as in most fractures) is determined by the energy of the injury.
Court-Brown et al (1998) reported the classification of 1500 ankle fractures according to the AO classification. Approximately half fell into groups which would be expected to be stable, although it is not clear to what extent they took into account clinical information in arriving at their conclusions. Barrie et al (2003) studied 300 ankle fractures, grouping them by stability (on clinical and radiological grounds) and by displacement. They also found 50% to be stable and undisplaced; of the remainder, half were potentially unstable but undisplaced, while one quarter of all the fractures were displaced. Even AO type C fractures were more likely to be undisplaced. McConnell et al (2004) carried out stress radiography on 97 undisplaced AO B fractures and found 61 to be stable and 37 unstable. Medial tenderness and bruising did not predict radiographic stability accurately. However, McConnell et al operated on all their stress-positive fractures; Barrie et al’s finding imply that many would have healed anatomically in BKW casts. Further trials are required for clarification.
Classification should give an indication of prognosis. Stable fractures do not displace even with axial loading out of splintage (see below). Fractures which are undisplaced at presentation, but are considered potentially unstable (usually because of tenderness over the deltoid) had a risk of displacement of 2.3% in Barrie et al’s study. Displacement which is not reduced has a significant risk of symptomatic degenerate change.
Clinical assessment
History
Patients with ankle fractures normally give a history of a fall or other injury mechanism. Absence of injury should make one consider a neuropathic fracture. Some patients hear a crack which is usually in favour of a major ligament injury or fracture. Other indications of the severity of injury include whether the patient was able to stand on the ankle, to walk, run, continue sport or other activity after injury.
Examination
A general survey of the patient should be undertaken, as meticulous as indicated by the history and severity of injury. There may be obvious malalignment of the ankle. If this is imperilling the skin over the medial side, the ankle needs to be reduced urgently. Inspect the skin and subcutaneous tissues for open fractures, fracture blisters and swelling.
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Fracture dislocation - needs reduction to protect medial skin |
Palpation of the acutely injured ankle should begin at the proximal fibula. The length of the fibula is palpated for tenderness, swelling or disruption to the bony contour, along with the tibiofibular interosseous area, especially the inferior tibiofibular joint. Clinical evidence of a malleolar fracture should be sought by palpation. If in doubt, stressing the malleoli by pushing the talus medially or externally rotating it may produce pain or displacement, but this is unnecessarily painful if there is already strong evidence of fracture. In undisplaced fractures, carefully examine the soft tissue of the medial side. Tenderness, swelling and bruising here are suggestive of a tear of the deltoid ligament and hence of potential instability. The calcaneum, midfoot and 5th metatarsal should also be examined.
Check the sensation, circulation and pulses. Examine the Achilles, long flexor and peroneal tendons.
Imaging
The standard plain radiographic views of the injured ankle are the mortise view and lateral. The mortise view is a modified AP with the ankle internally rotated so that the malleoli are in the same horizontal plane and the joint space is seen evenly on both sides of the ankle. This requires 10-20deg internal rotation. Adding a true AP view does not add useful information and should not be part of the standard series. We obtain ankle Xrays weightbearing when possible, but in the acute trauma situation the patient usually cannot comply fully.
The Ottawa ankle rules (Stiell et al 1994) have been shown to be accurate in predicting the need for radiography in the acute trauma situation. They can be used accurately by medical and nursing staff in a variety of settings, and can reduce unnecessary radiography. However, like many decision aids, their main function may be to ensure the practitioner carries out a proper clinical assessment.
Fractures with an unusual configuration or major plafond fragments may benefit from a CT to aid planning reconstruction
In the mortise view, the ankle joint “clear space” should be even on both sides of, and above, the talus. Lateral talar translation of more than 2mm is thought to imply a DTTL tear and, therefore, instability. However, Schuberth et al (2004) found that medial clear space was a poor predictor of arthroscopically-diagnosed deltoid injury.
On the mortise view, there is normally an overlap of at least 1mm between the fibula and the tibia (Pettrone et al 1983, Brage et al1997). Reduction of the overlap indicates syndesmotic instability.
The distal fibular fragment in AO B and C fractures is externally rotated relative to the proximal fragment. In stable fractures with an intact deltoid ligament, the distal fibular fragment is congruent with the talus and the mortise is congruent; the apparent external rotation is due to internal rotation of the proximal fragment by muscle action (Magid et al 1992, Harper 1995). However, in unstable injuries with a deltoid tear or medial fracture, the distal fibular fracture is truly externally rotated and the medial clear space is increased (Tang et al 2003).
Decision making
Clinical and radiological assessment of the severity of the injury will allow a rational treatment plan to be made:
- minor avulsion fractures, usually from the tip of the lateral malleolus (AO A1.2), represent ligamentous avulsions.
- fractures of the lateral malleolus through (AO B1.x) or below (AO A1.3) the syndesmosis without medial tenderness are normally stable. Certain features imply a more severe and potentially unstable injury even in this group:
- high energy injury
- open fracture
- severe bruising or swelling
- fracture comminution
- fractures with medial tenderness or medial malleolar fracture (AO A2+/B2+) are likely to have separation of the DTTL from the tibia and are therefore potentially unstable; some of these may represent superficial deltoid injuries only but there is no reliable way to differentiate superficial from deep deltoid injury
- fracture patterns which include a fibular fracture above the syndesmosis (AO C) have a variable and not entirely predictable syndesmotic injury (Nielson et al 2004) which makes them potentially highly unstable. If the DTTL is uninjured they may still be stable (even with a proximal fibular fracture) but this is probably not predictable enough to leave them free of splintage.
- the pathomechanics of isolated medial malleolar fractures is not well understood. Some are associated with significant injuries to the lateral and/or syndesmotic ligaments and may be unstable. a few are impaction or avulsion fractures, or form part of a partial plafond injury that is not clear on plain radiography. Truly isolated, undisplaced, medial malleolar fractures are probably stable injuries; displaced injuries are said to have a high incidence of symptomatic non-union because of interposed soft tissue, although there is little good evidence for this.
Management of stable ankle fractures
Fifty percent of ankle fractures are stable injuries:
- talus congruent in mortise
- trans- or infra-syndesmotic fibular fracture
- no medial injury
- no clinical evidence of higher-energy injury
In these fractures the risk of secondary displacement is extremely low. Two randomised controlled trial have shown that plaster treatment does not improve stability or outcome when compared with an ankle brace (Stuart et al 1989) or an elastic bandage (Port et al 1996). The long-term outcome after treatment without splintage is excellent (Bauer 1996). As these fractures do not displace, follow-up radiography is unnecessary (Michelson et al 1995, Martin 2004). Axial loading does not produce displacement (Michelson et al 1996), so weightbearing is permissible.
Therefore, these fractures require only symptomatic management. In practice, we find that the majority of patients are more comfortable in an ankle brace than elastic bandaging alone. However, the following are unnecessary and should be avoided unless clinically indicated:
- the use of casts
- avoidance of weightbearing
- follow-up radiography
Patients are encouraged to weightbear as soon as possible and to actively exercise the ankle. Follow-up is probably unnecessary.
Management of undisplaced, potentially unstable ankle fractures
This group make up 25% of ankle fractures. The talus is congruent in the mortise but there is a reason to suspect potential instability:
- medial tenderness or fracture (by far the commonest reason)
- higher-energy injury
- open fracture
- supra-syndesmotic fibular fracture
- posterior malleolar injury
The overall risk of secondary displacement is less than 5%. These fractures probably represent a spectrum from essentially stable to minimally displaced, and the redisplacement risk probably varies quite a lot, so careful clinical assessment is important.
There are no other data on which to base management. In practice we manage these in below-knee walking casts with early weightbearing. A weightbearing mortise view is obtained at one week and the cast is worn for six weeks. Weightbearing has the potential to produce displacement if the DTTL is torn, but as the risk is low and there is no evidence that nonweightbearing will alter it, we do not consider it necessary to insist on avoidance of weightbearing.
It must be emphasised that these recommendations are based on little evidence and may change in the light of current research.
Management of displaced ankle fractures
Only 25% of ankle fractures fall into this category, although they occupy most of the literature and textbooks.
Residual mortise incongruity increases the risk of late osteoarthritis, although many patients with some incongruity or even OA have few symptoms. Therefore, the goal of treatment is to restore tibiotalar congruity, maintain this until fracture union and provide opportunities for rehabilitation. Even with optimum treatment, most patients will have some residual symptoms at long-term follow-up and they need to be advised of this before treatment begins.
Initial management includes:
- management of other injuries
- management of open wounds with cleansing, dressing, documentation and prophylaxis against pyogenic infection and tetanus
- reduction of serious incongruity, especially if the medial skin is at risk
- splintage, usually in a plaster backslab
- pain relief
- explanation
Traditionally, most displaced ankle fractures were managed by closed reduction and casting, with prolonged nonweightbearing and follow-up radiography. Early internal fixation techniques emphasised stabilisation of the medial malleolus with screws, believing that the lateral malleolus contributed little to ankle stability. In 1977, Yablon published a group of biomechanical and clinical observations which led him to the conclusion that “the talus follows the lateral malleolus” and that the key manoeuvre in internal fixation of the ankle was accurate reduction and stable fixation of the lateral malleolus. Yablon’s work, along with stable fracture fixation techniques through the AO school, has led to open reduction and internal fixation of most ankle fractures as a standard technique. What is the evidence to support this change?
There are four randomised controlled trials comparing ORIF with closed reduction and casting (Bauer 1985, Phillips et al 1985, Rowley and Duckworth 1986, Makwana et al 2001). Makwana’s trial included only patients over the age of 55, and was the only trial to show any functional advantage at long-term follow-up for surgically treated patients. Rowley found that surgically treated patients took longer to recover normal movement and gait. Phillips’ paper is often quoted to show better outcomes in surgically treated patients, but in fact the clinical outcomes were the same – only the radiological outcomes were better after surgery.
These studies should not be taken to show that ORIF is unnecessary. For one thing, the post-operative management was restrictive (only Rowley et al allowed early weightbearing and none allowed early movement to surgically treated patients). Outcome measures were non-standardised and there was significant loss to follow-up in Phillips’ and Makwana’s series. In addition, there were patients in each series (10-30%) who could not be managed closed and required ORIF. Further trials, using modern methods of post-operative care, may show additional advantages for surgery.
However, this data would suggest that if the talus can be maintained under the tibia closed reduction and casting is an acceptable method of treatment. ORIF would be strongly indicated for:
- unstable fractures
- open fractures
- multiple injuries
- patients in whom ORIF and early functional weightbearing management would be expected to convey an advantage
If open surgery is planned, the ankle should be splinted and elevated to allow resolution of soft tissue swelling and blistering. Premature surgery is assocaited with an increased risk of wound complications. The patient needs to understand what can be achieved by surgery, that the ankle will not be entirely normal, and the risks of wound failure, infection and nerve injury.
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Surgical planning and technique is adequately covered in specialist manuals. The lateral side is normally stabilised first using lag screw and a neutralisation plate if technically possible. Fracture comminution may preclude a lag screw and the plate is then applied in bridging mode, preferably with minimal or no disturbance to the fracture site. In elderly osteoporotic patients fixation is difficult (though Makwana’s series suggests it is worth trying). Fibular nails have been described but their place is not yet clear.
The medial side is normally stabilised after the lateral side, using lag screws or tension band wiring. Occasionally one sees fractures where the fibula is so comminuted that length is difficult to establish, or the lateral soft tissues are very swollen, blistered or bruised: in such patients it may be worth reattaching the medial malleolus first (hence reattaching the DTTL).
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Syndesmotic injuries
Ankle fractures with a syndesmosis injury and interosseous membrane rupture (AO type C) are severe, potentially unstable injuries. Recent biomechanical and clinical studies have clarified these injuries and suggest a reduction in the need for syndesmotic stabilisation. As with other ankle fractures, an intact DTTL will protect against tibio-talar displacement even with severe syndesmotic tears – tears up to 15cm above the ankle have been studied in cadaver experiments. However, if the medial malleolus is fractured or the DTTL torn, a low syndesmotic tear (existing data suggest <4.5cm form the ankle joint line) may still be stable if the fibula is anatomically reduced and fixed. Above this, a syndesmotic positioning screw is likely to be needed. Unfortunately, the level of the fracture does not predict the level of the tear of the interosseous membrane very accurately (Nielson 2004). In addition, fibular stabilisation may sometimes be relative in these severe injuries, which often have significant comminution. Also, a combined injury of the medial malleolus and deltoid ligament may exist. Therefore, it is probably best to stress test all type C injuries after bony stabilisation. The syndesmosis should be stressed laterally, anteroposteriorly and in external rotation – Briggs et al (2004) suggested the main direction of instability is AP.
Biomechanical studies suggest a single 3.5mm cortex screw, through 3 cortices, about 2cm above the ankle joint line, is adequate for stability. The screw should be inserted with the ankle dorsiflexed to prevent narrowing of the mortise. It should be a neutral, not a lag screw. Occasionally a second screw is required in a highly-unstable fracture or a very large patient.
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Syndesmotic stress test leads to opening up (centre). 3-cortex syndesmosis screw inserted (right) |
It is generally advised to keep patients with syndesmosis screws non-weightbearing until the screw is removed at 6-12 weeks, lest the screw should loosen or break, usually the former. Only two studies have recorded outcome in patients who had were allowed to weightbear without screw removal. Although several screws became symptomatic, no patient had a poor outcome related to the screw or to ankle stiffness. We do not routinely remove syndesmosis screws, nor do we restrict weightbearing or ankle movement solely because of their presence. Screws which become symptomatic are removed, generally under local anaesthetic.
Posterior malleolus fractures
Fractures of the posterior malleolus almost always occur in association with a fracture of the lateral malleolus and a medial injury. “Isolated” posterior malleolar fracture should lead to suspicion of a proximal fibular (Maisoneuve) fracture and/or a major soft tissue disruption.
Hamaguchi et al (2006), using CT, found that 2/3 of posterior malleolar fractures were wedge-shaped and related to the posterior tibiofibular ligament, but 20% were transverse, extending in to the medial malleolus, and 15% were small posterior shell fragments.
A number of biomechanical studies suggest that tibiotalar instability occurs with a posterior fracture that separates 30-40% of the joint surface, in the posterolateral position, from the rest of the plafond. It is difficult to measure the proportion of separated joint surface from plain Xrays, as the fracture line is usually oblique. Ebraheim et al (1999) recommended the use of external rotation lateral views, although Hamaguchi et al (2006) found that the angle between the fracture and coronal plane varied unpredictably from -9 to 40 deg. Some studies suggest that adequate reduction of the fibula or an intact DTTL can prevent instability.
Clinical studies, however, have not shown a clear proportion of posterior separation that predicts a poor result. Both Harper (1988) and Jaskulka (1989) found that outcome was determined by the overall severity of the fracture and the adequacy of reduction. There have been no prospective clinical studies or trials.
At the moment we still recommend fixation of a large posterior malleolar fragment (over 25%). If this is unreduced after fibular stabilization we reduce it through a posteromedial approach. However, there is a great need for a RCT comparing fixation with non-fixation.
Post-operative management
General management after ankle fracture fixation is noncontroversial:
- reduction of swelling
- wound care
Traditional management would then be 6 weeks in a below-knee cast with varying amounts of weightbearing. Older series have used up to 12 weeks in a long leg cast.
The issues to be answered include:
- Does early mobilisation of the ankle followed by a period of casting produce better movement after removal of the cast? This was a popular method of post-op care 20-30 years ago but an RCT by Dogra and Rangan (1999) showed no advantage over simple casting.
- Does weightbearing affect the outcome, alone or in combination with mobilisation?
- Does protected mobilisation affect the outcome, alone or in combination with weightbearing?
Several small RCTs have addressed the latter two issues. There is no evidence that either weightbearing or early movement adversely affect outcome, and some evidence that they may have a small beneficial effect in the short to medium term. In addition, patients tend to prefer functional treatment rather than NWB casting. The non-casted patients in these trials were protected by ankle bracing or NWB exercise, rather than being left completely free. In practice we find that most patients prefer the support of an ankle brace which fits a trainer and allows weightbearing and ankle movement. However, Lehtonen et al (2003) reported a higher rate of wound problems in patients randomised to an Aircast brace instead of a cast. Application of the brace after wound healing seems to avoid this problem.
Currently there seems no reason to restrict weightbearing or mobilisation unless there are specific reasons to do so. Such reasons might include poor bone quality with limited stability of fixation, or patient compliance issues. Our default practice is to splint the ankle in a backslab or BKW cast until the wound has healed and then to mobilise in an ankle brace with weightbearing as tolerated.
Ankle fractures in the elderly
Ankle fractures in the elderly are associated with osteoporosis. They are more likely to have a stable configuration, especially in women (Barrie et al 2003), and can be treated in the same way as undisplaced fractures in younger patients.
Displaced fractures require reduction and stabilisation. Makwana et al (2001) showed a small advantage for ORIF over closed casting in the over-55 age group. However, bone stock in elderly patients may be poor and stable fixation difficult to achieve. Relative stability may have to be accepted and protected with a BK cast post-operatively. Nevertheless, good results can be obtained (Srinivasan and Moran 2001).
As an alternative to plating the lateral malleolus, fibular nailing has been described (Gehr et al 2004). Results were probably comparable with those of plating, possibly with fewer wound complications. An RCT comparing nailing and plating in the elderly would be useful.
Ankle fractures in diabetics
The risks of treating ankle fractures in diabetics are higher than in non-diabetics whether surgical or closed methods are used (Flynn et al 2000). Infection and skin breakdown are the main problems, and peripheral vascular disease, neuropathy and swelling increase the risk. The risk of wound failure after ORIF has been reported at 30-50%. In open fractures the wound complication rate is 60% and the risk of amputation may be as high as 40% (White et al 2003). RCTs would be needed to accurately assess the risk/benefit ratio of ORIF in displaced fractures in diabetics, but it would be difficult to do such a trial because of the heterogeneity of the patients and fracture patterns.
Most authors recommend 12 weeks of casting whether surgical or non-surgical treatment is used, with 6-12 weeks NWB depending on the severity of the injury and the presence of adverse factors. There is no clear evidence to support this, but until clearer evidence emerges prolonged protection, even in relatively low-risk patients, is probably best.
In addition a fracture of the ankle may precipitate Charcot arthropathy in diabetics with peripheral neuropathy (Kristiansen 1980,Thompson 1993, Holmes 1994, Connolly et al 1998). In high-risk neuropathic fractures trans-articular fixation (Jani et al 2004) may give better stability than traditional osteosynthesis.
As in treating any foot and ankle problems in diabetics, it is extremely important to assess the severity and control of the diabetic condition and the presence of peripheral vascular disease, neuropathy, cardiac and renal failure. At the moment it seems reasonable to treat fractures in non-neuropathic patients on the same principles as the general population, but warning of increased risks, protecting for longer and monitoring for late displacement. In neuropathic patients we would consider treating displaced fractures with retrograde nails.
References
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