Ankle ligament injuries are common:
- about 10% of all A+E attendances
- incidence of about 5/1000/year(Holmer et al 1994), which suggests about 300,000 per year in the UK or about 800 per day
Many ankle injuries occur in young people during sports: the mean age in Holmer’s series was 24y and nearly half were sports-related. Smith and Reischl (1986) found that half of a series of 84 college basketball players had chronic ankle injuries.
Some of those who suffer a sprained ankle develop recurring complaints. Verhagen et al (1995) followed up 577 patients treated by taping or reconstruction for 6.5 years. 18% had pain and about 40% had recurrent sprains or feelings of instability. Munk et al (1995) studied 79 patients 9-13 years after ankle sprains treated by various methods: 20% had persistent instability and 5% had pain.
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 retinaclum, 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 ATFL is the main stabiliser against anterior, varus and internal rotation stresses in plantarflexion and the CFL in neutral. With increasing dorsiflexion, the ligaments of the inferior tibiofibular joint probably play an increasing part in stability. The role of the deltoid ligament and particularly the DTTL in protecting against valgus and external rotation stresses is only beginning to be understood. The role of the posterior structures has had little study, probably because posterior displacement and forced dorsiflexion is an uncommon mechanism of ankle injury.
Acute injury
Most acute ankle ligament injuries occur when the ankle is plantarflexed. Hence, the ATFL is injured in almost all ankle sprains. Shoes with high heels, or a tight Achilles tendon, can predispose to such injuries. If the ATFL tears substantially, stress is thrown on the CFL and, occasionally onto the PTFL. Operative and MR studies suggest that about 20-40% of ankle ligament injuries include damage to the CFL and <10% to the PTFL. However, such studies will be biased towards more severe injuries, and the true incidence is unknown.
A few studies have described an injury pattern with the ankle in neutral or dorsiflexion, in which the CFL tears first and there is a higher incidence of joint surface injuries. Injuries to the deltoid ligament, either isolated or in association with the lateral ligaments, are increasingly recognised, particularly in people with a planovalgus foot.
Acute ankle ligament injuries are associated with a spectrum of other injuries to the hindfoot:
- tears of the inferior tibiofibular ligaments, especially the AITFL
- tears of the talocalcaneal ligaments
- joint surface injuries to the ankle
- tears of the peroneal tendons (usually peroneus brevis) and/or the superior peroneal retinaculum
- fractures of the tip of the lateral malleolus, the 5 th metatarsal base, the anterior calcaneal process or the lateral process of the talus
- traction injuries to the superficial peroneal or sural nerves
Clinical features
History
Most patients with an acute injury complain of a twisting or inversion injury of the ankle. Some complain of forced dorsiflexion or plantar flexion injuries and these may be different clinically. A clear history of inversion trauma is against a fracture but often the story is not this clear. 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.
Van Dijk et al (1996)found that the history of pain and swelling in the anterolateral aspect of the ankle had 96% sensitivity for an anterior talofibular ligament injury.
It is important to establish whether this is the first ligament injury or whether this is in fact an acute exacerbation of a chronic problem.
Examination
Examination 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. Alonso et al 1998 found that external rotation of the ankle is probably the most sensitive test for a syndesmotic injury; squeezing the tibia and fibula together with the ankle free or dorsiflexing the ankle while holding the malleoli together are also useful tests but interobserver variation with these tests was quite high and the predictive value was relatively low.
Clinical evidence of a malleolar fracture should be sought by palpation and stressing the malleoli by pushing the talus medially or externally rotating it, although this is unnecessarily painful if there is already strong evidence of fracture. The calcaneum, midfoot and 5th metatarsal should also be examined.
Tenderness is usually maximal over the lateral ligament, often the ATFL only. A few also have localised tenderness over the deltoid ligament; these tend to have more complex injuries. Some patients have rather generalised joint line tenderness, palpable synovitis or an effusion.
Tenderness or swelling over the Achilles, peroneal or tibialis posterior tendons should be identified. There is an association between ankle instability and peroneal tendon instability: the patient will usually complain of snapping or giving way over the peroneal tendons and instability is maximal on plantarflexion/eversion.
Instability is demonstrated with the anterior draw and tilt tests. The anterior draw test should be done with the ankle in 20deg plantar flexion (Bahr et al 1997 – a cadaver study). The tibia may be pushed posteriorly against a fixed foot or the foot drawn forwards. The characteristic positive sign is a "suction sign" as the synovium is sucked into the joint drawing the skin inwards in the lateral gutter. However, in many patients there is no suction sign but the talus can obviously be drawn anteriorly more than on the other side.
The talar tilt test is conventionally performed by tilting the hindfoot and looking for a suction sign or asymmetrical movement. It should be done with the ankle plantigrade (Bahr 1997). Palpation of the talar neck will assist in differentiating between movement in the ankle and the subtalar joint. No clinical work has been done to examine the accuracy of the draw and tilt tests.
Examine the skin and subcutaneous tissues for open fractures, fracture blisters and swelling. Check the sensation, circulation and pulses. Examine the Achilles, long flexor and peroneal tendons, and assess peroneal stability. There is an association between lateral ligament injuries and peroneal tendon tears and instability.
Van Dijk et al (1996) studied diagnostic strategies for lateral ankle ligament disruptions. They found the most reliable test was clinical examination of the ankle by a senior orthopaedic surgeon after 5 days (to allow swelling and pain to improve). The sensitivity of this procedure was 96% and the specificity 84%. Examination after 5 days by a well-instructed trainee was almost as accurate. No diagnostic imaging was as accurate as the clinical examination although the cost was much higher. Examination at the time of injury was also less accurate, although this was not by senior staff so is not strictly comparable. The study considered only patients with acute ligament tears and the gold standard was surgical exploration. Examination by other personnel such as physiotherapists was not studied. This study gives strong support for a primarily clinical approach to diagnosis of these injuries.
Investigation
Investigation of patients with acute ankle ligament injuries is basically diagnostic imaging of various sorts. Other investigations may be indicated on a case by case basis.
Plain films
The standard plain films of the ankle are mortise and lateral views. Radiography is not indicated in all acute ankle injuries. The Ottawa Ankle Rules have been proven to reduce unnecessary radiography while ensuring a high level of recognition of fractures. As well as malleolar fractures, plain films may show osteochondral injuries of the talus, lateral and posterior talar process fractures, avulsions of the superior peroneal retinaculum and calcaneal fractures. However, plain films will not generally demonstrate ankle ligament tears or instability.
Stress views
Stress radiographs of the ankle have come to be considered the gold standard for the diagnosis of acute and chronic ligament injuries. An anteroposterior view with the hindfoot in maximal varus and a lateral with the hindfoot drawn anteriorly relative to the tibia are the standard views. Films of both ankles should be obtained for comparison. Frost and Amendola (1999) give a useful systematic review of stress radiography.
There is disagreement on many technical aspects of stress radiography. Stress radiography in the acutely injured ankle is painful. General and regional anaesthesia have been suggested to improve the accuracy of measurements. Becker et al (1993) showed that the anterior draw test gave greater values in both normal and injured ankles after peroneal nerve block, the difference being greater in the injured ankles. However their paper does not show whether this increased the diagnostic value of the test.
Ultrasound
In skilled hands, ultrasound has been shown to be technically capable of diagnosing acute ligament tears Campbell et al 1994). Van Dijk et al included ultrasound among the diagnostic modalities they studied and found it to be less accurate than clinical examination. In addition, the move away from acute ligament reconstruction has rendered the information from ultrasonography of the acutely injured ankle less relevant to the care of the patient.
MR
Magnetic resonance imaging allows evaluation of the ankle ligaments and also the tendons and bones. Studies in acutely injured ankles (Frey et al (1996), Magee and Hinson (1998), Tochigi et al (1998)), show associated injuries to the talus, subtalar ligament injuries and tears of the tibialis posterior and deltoid injuries, and some of these were associated with poorer outcome. In patients scheduled for surgical stabilisation of chronically unstable ankles, Chandnani et al (1994) showed MR arthrography to be superior to MR imaging and stress radiography for the detection of ATFL and CFL tears. MR is superior to plain radiography for the diagnosis and evaluation of osteochondral lesions of the talus (Hepple et al 2001). However, there have been few studies of how MR alters decision-making. In addition, MR cannot demonstrate instability without dynamic images.
We use MR:
- in patients with persistent severe pain after an acute injury, usually 4-8 weeks after injury. these patients may have intra-articular injuries which are amenable to arthroscopic treatment (Hepple et al 2004)
- in patients who fail rehabilitation for a chronic injury where pain in the joint (rather than impingement pain) is a significant problem, or where injection of an apparent impingement lesion is unsuccessful. the goal of the test is to look for an osteochondral lesion to support a decision on whether to offer an arthroscopy, and to guide visualisation at arthroscopy in what can be a tight ankle.
Management of acute injuries
Most ankle ligament injuries are stable and clearly should be managed conservatively. The nature of this conservative management varies from simple advice and symptomatic management to prolonged rehabilitation programmes with or without bracing. Many patients with chronic injuries consider themselves to have “had physiotherapy”, but this often amounts to some exercises and a bit of ultrasound.
Early bracing (Leanderson and Wredmark 1995) does not alter the final outcome but allows quicker recovery. A number of studies (Goldie et al (1994), Wester et al (1996), Holme et al (1999)) suggest that active rehabilitation of ankle ligament injuries produces some improvement of results. The treatment regimes aim at improving flexibility, peroneal strength and proprioception. However, the differences are quite small, and the treatment in the control limbs of the studies were very different: control groups in some studies received more treatment than treatment groups in other studies. Recruitment methods may have introduced some bias. It is not yet possible to conclude what regime of treatment is most cost-effective.
There have been a number of randomised controlled trials of surgical versus non-surgical treatment of acute ligament tears, most of which were meta-analysed by Pijnenberg (2000) – although this paper has implicit flaws. Almost all trials treated their non-surgical patients in cast. Pijnenberg et al (2003) reported a trial in which patients were randomised to surgical repair with early mobilisation and rehabilitation or mobilisation and rehabilitation without repair. The repaired patients reported less late instability and pain, but apparently had not required further treatment for this. Pijnenberg considered the clinical difference too small to warrant routine acute repair.
Kitaoka et al (1997) reported a retrospective study of 53 injured ankles in 48 patients followed up for 12-33 years. 22 ankles in 21 patients underwent primary repair. 31 ankles in 27 patients underwent either an Evans or a Watson-Jones procedure for late instability. Treatment was at the discretion of the admitting physician and, of course, ankles which were successfully treated without surgery were not included. There was no difference in objective stability on stress radiography and structurally unstable ankle at final follow-up were often asymptomatic. Outcome using an ankle score and patient satisfaction showed no difference between the groups. As this was not a RCT there are many possible confounding factors. However, this study shows similar outcomes whether ankle ligament injuries are all treated by repair, or reconstruction is performed only when non-surgical treatment fails.
Our practice for acute injuries is:
- Patients with ankle injuries should be assessed by an experienced clinician.
- Ankle ligament injuries should be diagnosed on the basis of tenderness, swelling or bruising over the ligaments.
- The diagnosis of instability should initially be made on clinical examination by an experienced clinician; in case of doubt the examination should be repeated at 48-72 hours
- Ankle radiographs should only be requested as indicated by the Ottawa Rules
- No other imaging is indicated in the acute setting.
- Minor stable injuries should receive advice on self-care (RICE regime), on the natural history of the condition and on how to obtain advice should the ankle fail to settle.
- Major stable injuries, with severe pain and swelling, should be seen by the Physiotherapy Clinical Specialist or the Foot and Ankle Service physiotherapists
- Unstable injuries should be offered an ankle brace and referral to the physio ankle rehab programme in the Foot and Ankle Service
- Recurrent injuries should be offered a referral to the physio ankle rehab programme in the Foot and Ankle Service
- Injured ankles which are failing to settle should be referred to the Foot and Ankle Service for an opinion on further investigation and treatment, particularly to exclude an osteochondral injury.
- Persistent severe pain is normally an indication for early MR
- Surgery should not generally be offered for acute ankle ligament injuries
- Early arthroscopy may occasionally be advised
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