NB This page is from the 2005 Hyperbook.
Last evidence check February 2007 but no substantial revision since Feb 2005.
Ankle ligament injuries are common:
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.
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.
As Munk and Verhagen showed, a significant proportion of patients develop chronic symptoms after an ankle ligament injury:
The amount of disability form such symptoms has not been studied in detail. As many ankle injuries occur during sport, difficulty in returning to sport is a common complaint.
It might be assumed that persistent giving way and re-injury of an ankle is because the ligaments, having been torn, no longer contribute to stability and therefore there is excess movement in abnormal directions. In fact, many patients believe this and expect that they need the ligaments repaired. However, not all patients with chronic ankle symptoms have abnormal ankle movement, even if their main symptom is giving way.
Freeman (1965) introduced the terms functional and mechanical instability. Functional instability is the complaint of giving way of the ankle; some have also used the term for a feeling that the ankle is about to give way. Mechanical instability is abnormal movement of the talus within the ankle mortise, usually demonstrated on stress radiography. Not all patients whose ankles give way (who have functional instability) have mechanical instability, and not all patients who have mechanical instability have functional instability.
The definition of mechanical instability varies from paper to paper. The most precise investigation was that of Karlsson et al (1991b). They measured anterior draw and tilt radiographs (see below for definitions) in 200 normal controls without ankle problems, 63 patients with bilateral functional instability and 57 with unilateral functional instability, using a stress jig. Their criteria for mechanical instability were chosen for maximum discrimination between the functionally stable and unstable groups: 10mm or more of anterior draw and/or 9deg or more of talar tilt. Where a contralateral functionally stable ankle was available for comparison, criteria of 3mm excess anterior draw or 3deg excess talar tilt were advised. Karlsson et al also documented the interobserver variability in measurement. However, few other authors have found such a close relationship between functional and mechanical instability.
Many factors, other than mechanical instability, have been advanced to account for chronic ankle instability:
In addition, the associated injuries listed above may produce pain, altered function and even loose bodes in the ankle. There is evidence to support the presence of all the above factors, but not enough data to determine which factors are most important.
The main biomechanical factors are
hindfoot alignment : a varus hindfoot will tend to impose a varus/internal rotation force on the ankle, and in addition tends to limit the amount of compensatory movement available in the subtalar and midtarsal joints. Thirty percent of patients with cavovarus feet have ankl einstability (Barrie et al 2000). Some cause of hindfoot varus, such as Charcot-Marie-Tooth disease, are also associated with peroneal weakness. A valgus hindfoot may place additional stress on the deltoid ligament and is associated with chronic medial ankle instability.
tight Achilles tendon : limited ankle dorsiflexion means that the ATFL has to stabilise the ankle through more of the gait cycle and places more stress on a weakened ligament
However, the role of biomechanics has had little scientific evaluation as yet.
Most patients with chronic instability give a clear history of one or more ankle injuries. However, some, especially those with varus or cavovarus deformity, develop symptoms of ankle instability without injury. Typically patients complain of repeated giving way of the ankle which is usually painful. Swelling may accompany episodes of giving way. Giving way is often commoner on slopes or uneven ground. In some patients the predominant complaint is pain or locking: this should raise a suspicion of intra-articular pathology such as an osteochondral fracture.
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.
Anterior draw test |
Talar tilt test |
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.
It is important to identify underlying causes of chronic instability. In particular the overall foot shape should be evaluated, looking particularly for hindfoot varus, and an adequate neurological examination should be performed. The shoes will give information on heel contact. Generalised joint laxity should be sought.
In the chronic injury, pain in the joint line is often due to impingement from post-traumatic synovitis, sometimes exacerbated by a spur on the tibia or talus. This can be demonstrated with the Molloy impingement test (Molloy et al 2003). A finger is placed in the joint line and the ankle dorsiflexed, producing or increasing the pain. This should be tried across the anterior joint line and in the medial and lateral gutters. Pain which is worse on palpation rather than dorsiflexion, especially over the talar articular surface, should suggest an osteochondral lesion.
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.
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.
In patients with a chronic history which is mainly of instability, radiographs are not routinely required. Where pain is a significant feature, plain AP and lateral radiographs of the ankle are generally obtained to evaluate the joint and look for associated injuries. We obtain these films standing to get an accurate assessment of joint space and alignment. However, plain films will not show 50% of osteochondral injuries, or soft tissue injuries such as peroneal tendon tears. No studies have examined the diagnostic yield of plain films in the chronically unstable ankle.
In patients with cavus or cavovarus feet we also obtain a standing hindfoot alignment view (Salzmann and El-Khoury 1995), which differentiates between malalignment within and below the ankle. Standing lateral and dorsoplantar views of the foot allow further evaluation of the deformity. Oblique hindfoot views may be obtained in cases of suspected subtalar pathology or fracture of the anterior calcaneal process.
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| Anterior draw stress Xray | Tilting stress Xray |
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.
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.
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:
Most papers on surgery for chronic instability comment that "the patients had full non-surgical treatment before being considered for surgery" and this is considered good practice (Karlsson and Lansinger 1993, Trevino et al 1994).
However only one published series examined the effect of functional rehabilitation on chronic instability. Karlsson (1991a) found that 50% of patients with chronic instability benefited from rehabilitation. Patients with mechanical instability were less likely to benefit than those with purely functional instability.
The studies of Schafer and Hintermann (1996), Kibler (1996) and Ogilvie-Harris et al (1997) found a high incidence of intra-articular pathology:
About a quarter of intra-articular lesions were not identified pre-operatively. Laing et al (2004) found that arthroscopic treatment of intra-articular lesions avoided the need for surgery in patients with demonstrated mechanical instability.
It is our practice to offer an examination under anaesthesia, stress radiographs and arthroscopy to all patients with persisting functional instability after a functional rehabilitation programme. This allows us to treat intra-articular pathology and identify those with mechanical instability who can be offered a stabilisation procedure. It also identifies the small group with combined ankle and subtalar instability for whom a Sammarco tenodesis rather than a modified Brostrom procedure is appropriate. Approximately 40% of our patients have had only an arthroscopic procedure. Patients with mechanically stable ankles and other intra-articular problems have generally had good results from arthroscopic surgery. Patients with unstable ankles will be offered a stabilisation procedure. We prefer to perform this about 6 weeks after the arthroscopy rather than at the same sitting because of the amount of swelling that tends to accompany an ankle arthroscopy.
There are two main approaches to surgical stabilisation:
Biomechanical studies (Liu and Baker 1994, Hollis et al 1995, Bahr 1997) show that, if anything, the Brostrom-Gould procedure confers more stability and more normal ankle kinematics than any of the non-anatomical tendon grafts. The Bahr anatomical tendon graft also produced kinematics close to normal.
There have been two randomised controlled trials comparing the Brostrom to non-anatomical reconstructions. Both had significant methodological deficiencies. Neither showed any difference in functional outcome between the trial groups.
Longitudinal studies of single procedures report:
Because it is simple, restores near-normal ankle kinematics and has a fuller long-term clinical outcome evidence base than the anatomical tendon grafts, we advise that the Brostrom procedure is to be preferred in the average patient. For the more complex case we offer the Sammarco anatomical tenodesis, accepting that further long-term results may influence this advice. Indications for the Sammarco procedure include:
Standard post-operative regimes after ankle ligament reconstruction involve 4-6 weeks in a below-knee cast, sometimes with a period of non-weightbearing. Karlsson (1995, 1999) reported trials comparing casting with walker boots and ankle braces, finding no deterioration in outcome with these simpler and more comfortable supports. Wearing a plaster cast is not necessary after an ankle ligament reconstruction and delays functional recovery. We manage our patients in functional braces from the beginning, except for an initial 48 hours splintage in a backslab to allow post-op swelling to settle.