Introduction

The acute ankle ligament injury is the most common type of injury seen by general practitioners and emergency departments. They represent 25% of all injuries of the musculoskeletal system with over 20 000 patients in the U.S. each day. In about 10 to 15 percent of all inversion trauma, a rupture of the lateral ankle ligaments is present.
In most cases, a lateral ligament injury occurs with the foot rotating inwards in plantar flexion when the tibia is simultaneously rotating outwards, giving rise to anterolateral rotational movement. The medial malleolus acts as a fulcrum when the ankle moves into increased inversion, losing its stabilizing function and increasing the strain on the lateral side.
Ankle ligament injuries are usually classified as Grade I (mild), Grade II (moderate) and Grade III (severe). Grade III injuries always include a complete rupture of the ligaments and the joint capsule, with severe bruising, swelling and pain. There is a major loss of function, reduction of motion and increased laxity due to the ligament rupture. The value of this classification is doubtful, since a partial rupture or isolated capsular lesion (grade I) is present in less than 1% of cases. The outcome of several studies has shown that there is no difference between the prognosis of a single (grade II) or a multiple ligament rupture (grade III). Therefore, it is important to distinguish a simple sprain from a ligament rupture after supination trauma. 
A rupture of the anterior talofibular ligament occurs as an isolated injury in 50-75% of cases. A partial rupture of this anterior talofibular ligament or an isolated capsular lesion is present in only 1% of patients after a supination injury. With an increasing force, the calcaneofibular ligament is also ruptured. A rupture of both the anterior talofibular ligament and the calcaneofibular ligament occurs in 15-25%. Isolated rupture of the calcaneofibular ligament happens in approximately 1% and injury to the posterior talofibular ligament is rare.
A rupture of the anterior tibiofibular ligament does not usually result in symptoms or degenerative changes at long-term follow-up. It is concluded that this rupture of the anterior tibiofibular ligament does occur in 1 - 5% of the patients after severe inversion trauma of the ankle.

Anatomy

The ankle joint is the most congruent joint of the human body. Stability is provided by the bony configuration of the ankle mortise and the talar dome and by the ankle ligaments. During ankle motions, both rotation and translation around and along the movement axes occur. Soft tissue stability is mainly provided by the ligaments; these are the tibiofibular syndesmosis superiorly, the deltoid ligament on the medial side and on the lateral side, the anterior talofibular ligament, the calcaneofibular ligament and the posterior talofibular ligament. 

The anterior talofibular ligament can be considered to be an intra-articular reinforcement of the joint capsule. This ligament is the main stabilizer on the lateral aspect of the ankle and the most vulnerable to injuries. The orientation of the anterior talofibular ligament is in a plane parallel to the axis of movement (flexion-extension), provided the ankle is in a neutral position. Thus, the anterior talofibular ligament is a true collateral ligament when the foot is placed in plantar flexion. However, most ankle ligament injuries occur by internal rotation in equinus position with the foot in plantar flexion, when the narrowest part of the talus is placed in the ankle mortise and the ankle is thus rendered most lax. This is probably one important reason for the high incidence of injuries of the anterior talofibular ligament.

The extra-articular calcaneofibular ligament arises from the anterior part of the tip of the fibula. It runs obliquely downwards and backwards to be attached to the lateral surface of the calcaneus. There is a great variety in direction and in proximal attachment. Usually the main part attaches to the tip of the fibula, and in most cases, a bundle of fibers runs directly to the anterior talofibular ligament as well. In some cases, the calcaneofibular ligament attaches predominantly to the anterior talofibular ligament.
In contrast to the anterior talofibular ligament, it is not part of the fibrous capsule but separated from it. It is intimately associated with the posteromedial part of the peroneal tendon sheath. It bridges the talocrural as well as the subtalar joint. 

The posterior talofibular ligament is a short and thick ligament. The posterior talofibular ligament is tight with the ankle in extension and lax in plantar flexion. Injuries to this ligament are infrequent, and the ligament is not used as a part of a reconstructive procedure. 

Anatomic variations in shape, size, orientation and capsular relations of the lateral ankle ligaments are common; up to 75% of subjects show some variation, most commonly the calcaneofibular ligament. The anterior talofibular ligament is divided into two separate bundles in one-third of all patients. These anatomical variations should be born in mind when deciding upon treatment of ankle ligament injuries, especially when considering surgical reconstruction of the calcaneofibular ligament.

History & Physical Examination

Chronic ankle instability develops in approximately 20% of patients after acute ligament rupture. 
Clinical tests for acute and chronic ankle instability can be divided into the talar tilt test and anterior drawer test. The talar tilt test is clinically impractible and most often unreliable. The anterior talofibular ligament is the most important stabilizer of the ankle joint. It is the first ligament to rupture during an inversion trauma. Therefore, the anterior drawer test is the most important test for detection of acute and chronic ankle instability.
Increased anterior translation of the talus in the talocrural joint can occur when the anterior talofibular ligament is ruptured or elongated. There are several ways of performing an anterior drawer test.
In most test situations the foot is moved only anteriorly relative to the tibia. The ankle thereby is placed in 10° to 20° of plantar flexion. This is an incorrect way to perform the anterior drawer test and is associated with a higher risk of false-negative test results. It has been shown that the anterior drawer is not a straight forward translation of the talus in relation to the tibia, but that it is rather a rotatory movement. This rotation is caused by the intact deltoid ligament which prevents the talus to move forward on the medial side. The anterior drawer test should therefore be a combination of a straight forward translation and internal rotation movement.

Diagnostic Imaging

Knowledge of the laxity of the ankle joint ligaments in both the sagittal and the frontal planes can give a valuable pattern of information during the diagnostic assessment of chronic functional instability. Radiographic measurements of ankle joint stability are often used before deciding upon the operative treatment of chronic ankle instability.
The two radiographic tests which are used are the lateral instability/laxity test (talar tilt) and the anterior instability/laxity test (anterior talar translation). Increased laxity can be defined either as a single value of anterior talar translation > 10 mm or talar tilt > 9 degrees. Another way of defining increased laxity is a difference of anterior talar translation > 3 mm, i.e. the difference in anterior talar translation between the functionally unstable ankle and the contralateral ankle and/or talar tilt > 3 degrees in patients with unilateral instability.32,33 A good correlation between functional and mechanical instability has been shown in some studies, but this correlation is highly variable, since several factors other than mechanical instability can be responsible for the development of functional instability.

Surgical treatment

Less than 10% of all subjects who have sustained acute ligament injuries will need stabilizing surgery at a later stage. Before deciding upon surgical treatment in a patient with chronic ligament insufficiency, a supervised rehabilitation program based on peroneal muscle strengthening and co-ordination training should always be carried through. More than half of these patients will regain satisfactory functional stability after 12 weeks on such a program. Patients with high-grade mechanical laxity have less favorable prospects in regaining satisfactory function by physiotherapy. In these patients surgical treatment should be considered at an earlier stage.
More than 60 different surgical procedures to stabilize the unstable ankle have been described in literature. These procedures can be divided into two main groups:
1.  tenodesis
2. anatomical reconstruction

The basic principle of anatomical reconstruction is to restore the normal anatomical ligamentous proportions which should lead to the original biomechanical situation of the lateral ligament complex of the ankle joint. For the anterior talofibular ligament anatomical reconstruction is relatively simple. The insertion at the tip of the fibula and the talus is quite uniform. Most anatomical textbooks describe the existence of a single anterior talofibular ligament. In a certain percentage (approximately 10-30%), anatomically as well as functionally, an upper and a lower part of the ligament may be distinguished. The insertion of the calcaneofibular ligament at the tip of the fibula is also uniform. It arises from the anterior part of the fibula. It runs obliquely downwards and backwards to be attached to the lateral surface of the calcaneus. This insertion point is less unambiguous. In the plantigrade foot there is interindividual direction of the calcaneofibular ligament, which lies between 10° to 80° posteriorly. There is also a considerable interindividual variety in the length of the calcaneofibular ligament. After a rupture of this ligament it is, therefore, difficult to identify its original insertion at the calcaneus. It is, therefore doubtful whether anatomical reconstruction of the calcaneofibular ligament is at all possible.

Anatomical reconstructions can be classified into four categories:
1.  anatomical reconstruction using the original ligament remnants
2. anatomical reconstruction using the original ligament ends with reinforcement of local tissues like                      periostium, inferior extensor retinaculum etc 
3. anatomical reconstruction using an autograft
4. anatomical reconstruction using an allograft

In the instructional video, the anatomical reconstruction using original ligament remnants are presented. Broström who described this procedure in detail, found that direct suture (repair) of the ruptured and elongated ligaments was possible, even several years after the primary injury. The combination of shortening, imbrication and reinsertion to the bony attachment of the injured ligaments has been successful. Satisfactory functional results after anatomical reconstruction of the lateral ankle ligaments have been described in several studies. The surgical technique is simple and easily performed. The damaged and/or elongated remnants of the anterior talofibular ligament and calcaneofibular ligament are divided, shortened 3-5 millimeters, imbricated and reinserted into bone.

Satisfactory functional results have been reported in approximately 90% of patients, with radiographic evidence of less residual laxity. The results are, however, less satisfactory in patients with generalized hypermobility of the joints, very long standing ligamentous insufficiency (over 10 years) and in patients who have undergone previous ankle joint ligament surgery. 
Anatomical reconstruction using the original ligament ends has been found to be technically simple, giving rise to few complications and producing satisfactory functional results in both the short- and the long-run.

Recommended Literature

Klenerman L. The management of sprained ankle. J Bone Joint Surg Br. 80: 11-2, 1998.

Van Dijk CN. On diagnostic strategies in patients with severe ankle sprain. Thesis, Universiteit van Amsterdam, Amsterdam, The Netherlands, 1994.

Karlsson J, Lansinger O. Lateral instability of the ankle joint. Clin. Orthopaedics and Related Research 276: 253-61, 1992.

Karlsson J, Bergsten T, Peterson L, Zachrisson BE. Radiographic evaluation of ankle joint stability. Clin J of Sports Medicine I: 166-71, 1991.

Kerkhoffs GM, Blankevoort L, Sierevelt IN, Corvelein R, Janssen GH, van Dijk CN. Two ankle joint laxity testers: reliability and validity. Knee Surg Sports Traumatol Arthrosc. Jul 19; 2005 

Van Dijk CN, Mol BW, Lim LS, Marti RK, Bossuyt PM. Diagnosis of ligament rupture of the ankle joint. Physical examination, arthrography, stress radiography, and sonography compared in 160 patients after inversion trauma. Acta Orthop Scand 67: 566-70, 1996.

Krips R, van Dijk CN, Halasi T, Lehtonen H, Moyen B, Lanzetta A, Farkas T, Karlsson J. Anatomical reconstruction versus tenodesis for the treatment of chronic anterolateral ankle instability; a 2- to 10- year follow-up, multi-center study. Knee Surg Sports Traumatol Arthrosc; 8(3):173-9, 2000.