These are the current techniques for testing and treating acute lateral ligament injuries of the ankle
Lateral ligament injuries of the ankle are possibly the most common sporting-related injuries, on average making up 10-15% of such injuries. One large study of 12,000 sporting injuries(1) showed that 25% involved the foot and ankle and the majority of these involved the lateral ligament complex. It is estimated that the incidence is one per 10,000 of the population per day. This frequency has obvious implications for the athlete, and to health care economics worldwide.
This article focuses on current evidence concerning the management of acute injuries, but it is also necessary to mention some anatomical and aetiological factors, as well as describing the classification in order to better understand treatment rationales.
The position of the foot dictates the injury
The lateral ligament complex has three thickened portions, though these are variable. The anterior talo-fibular ligament (ATFL) is lax when the ankle is in neutral, but is taut in plantarflexion when it acts as a collateral ligament. The calcaneo-fibular ligament (CFL) is taut in neutral. Finally, the posterior talo-fibular ligament (PTFL) is a strong structure rarely injured in inversion injuries but may be associated with avulsion fractures of the posterior talar process. The bony anatomy of the talus, with the anterior part of the articular surface being wider than the posterior part, means that dorsiflexion is the position of 'close pack' where
the bony constraints are at their greatest. Therefore, with increasing plantarflexion the lower are the bony constraints and the greater the likelihood of ligamentous injury. In general, this means that the position of the foot when injured dictates the injury sustained, with the syndesmosis at risk in dorsiflexion, the CFL at risk in neutral and the ATFL at risk in plantarflexion. This is reflected in the rates of ligamentous injury. In Brostrom's series the ATFL was injured in 65%, the CFL in 29% and the PTFL rarely.
The medial or deltoid ligament is much less frequently injured in isolation. Brostrom quoted a rate of 3% in his series. Ruptures are almost always associated with ankle fractures. Similarly isolated syndesmosis injuries are rare in the absence of a fracture though injuries to the anterior inferior tibio-fibular ligament are increasingly recognised in sports such as football.
Most at risk: basketball, volleyball, soccer
The aetiology of inversion injuries to the ankle is unsurprising, with certain sports being particularly at risk, including basketball, volleyball and soccer. An interesting question is the role of hypermobility or generalised ligamentous laxity. One study of ballet dancers has shown increased rates of injury in dancers exhibiting hypermobility. Another factor is the role of footwear and playing surface, the so-called 'shoe surface interface'. Several studies have shown a reduction in ankle injury rates by changing athletes' footwear.
The grading of lateral ligament injuries is obviously important in guiding treatment. The most common system, popularised by Chapman(2) and by Balchini, describes three grades of injury. Grade I (mild) involves the ligament stretching without a tear. There is little swelling or tenderness, minimal functional loss and no instability. Grade II (moderate) is a partial macroscopic tear with moderate swelling and tenderness, decreased range of movement and mild or moderate instability. Grade III (severe) is a complete rupture with swelling, haemorrhage and tenderness, abnormal joint movement and instability. The difficulty with the use of this classification is in the definition of 'mild', 'moderate' and 'severe' instability. The presence of a firm end point on ligamentous testing has been used as a guide, but there is wide normal variation as well as difficulty interpreting the clinical tests. This makes the clinical differentiation between grades II and III difficult in some situations. This in turn has implications for treatment, which will be discussed below. Also, this system does not differentiate between components of the lateral ligament complex and it is therefore necessary to include this in one's assessment. The history, i.e. the position of the foot and forces involved, will contribute to an accurate diagnosis being made.
The common clinical tests used to assess lateral ligament instability are the anterior drawer test and the talar tilt test. The anterior drawer test is performed with the leg flexed and relaxed, e.g. over the side of the bed, one hand grasping the leg and the other the heel. Forward pressure is exerted to the heel with counter force to the distal tibia and the degree of anterior translation of the talus is assessed. A difference of 3-5mm between sides is considered significant and is predominantly a test of the ATFL.
The talar tilt test or inversion stress test is performed in the same position and a varus force is applied to the heel. In maximal dorsiflexion the contribution of the subtalar joint is minimised and the calcaneo-fibular ligament is taut. This is a test predominantly of the calcaneo-fibular ligament. It is important to remember to perform both tests in at least two positions to test the relative contribution of the different ligaments. Interestingly, despite much research, it is still not fully understood exactly which structures are being tested when performing these tests. As mentioned above, these tests are subjectively graded as mild, moderate and severe and examination of the contralateral, uninjured limb is necessary for comparison.
Various investigations have been used to confirm the clinical diagnosis and to choose a treatment regime. One of the most common is the stress radiograph. A recent review of the literature from Canada(3) looked at the published data on the talar tilt and anterior drawer stress X-rays. They concluded that, due to both the variation in normal values and the lack of correlation between treatment choice and instability on
X-ray, stress radiography has no place in the diagnosis of acute lateral ligament injuries. Magnetic resonance imaging has become much more widely available during the last decade, and seems to be particularly good in the assessment of lateral ligament injuries. A study from Germany(4) demonstrated MRI as being 100% accurate in diagnosing ATFL injuries, though slightly under reporting CFL injuries. Interestingly this study also recommends MRI in the monitoring of conservatively treated ruptures.
Treating Grade I and II injuries
The treatment of Grade I and Grade II lateral ligament injuries is not debated. 'Functional treatment' including RICE and short semi-rigid immobilisation followed by early motion exercises, then early weight bearing and neuromuscular ankle training is well described, and its timing dependent on the severity of injury. Jackson showed in West Point cadets the duration of disability to be eight days for grade I injuries and 15 days for Grade II. A recent Danish study(5) highlighted the benefit of supervised training in reducing re-injury rates.
In randomised controlled trials, most adjuvant therapies such as ultrasound and various current therapies, have not been shown to be beneficial. Only cryotherapy has been shown to be of benefit.
Grade III injuries
The treatment of grade III injuries (i.e. complete ruptures), and particularly the role of surgery, remains controversial. Many authors have examined a variety of treatments including functional treatment, rigid (cast) immobilisation and primary surgery and made recommendations as to when surgery is indicated and which procedures to perform. A review in 1999(6) recommended a conservative approach with or without rigid immobilisation, reserving surgery for chronic instability, arguing that the success of late surgery was as good as primary. However, these authors do report a rate of 10-30% of injuries developing chronic symptoms. In 2000 a Meta-analysis(7) of randomised, controlled trials concluded that no treatment leads to greater residual symptoms. Operative treatment produces better results than functional treatment and that functional treatment leads to better results than cast immobilisation. In general, surgical treatment in the acute rupture is now accepted to employ a primary ligament repair type procedure, though diagnostic accuracy is required to determine which ligament is injured and therefore the appropriate surgical intervention. Currently, the Brostrom-Gould procedure is probably the most popular one, and many authors have published excellent results.
Finally, and influencing the need for surgical intervention, is the presence of associated injuries. The differential diagnosis of lateral ligament injuries includes fractures, stress fractures, osteochondral injuries, midfoot ligament sprains, capsular injuries and peroneal injuries. Careful evaluation and appropriate investigation is essential to avoid misdiagnosing lateral ankle injuries or missing associated injuries, which could affect treatment outcome.
Phillip Ahrens and
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