Anterior talo-fibular ligament (ATFL) tear

Anterior talo-fibular ligament (ATFL) tear: an often missed injury, diagnosis and repair: a brief discussion

Anterior talo-fibular ligament (ATFL) tears are a common injury seen in the emergency department and office. However, a majority of these injuries are diagnosed as a sprain, and an Aircast, or brace of some sort, is dispensed. Moreover, there is a lack of a formalized, or standardized evaluation and treatment in the emergency department and/or primary cares office. This short article discusses a cost effective modality of determining whether the ATFL is intact or torn, and a reliable method of repair.
The ATFL is a ligament that is part of the ankle capsule (intra-capsular) (fig 1). The ligament is approximately 2mm thick, 7mm wide, and 25mm long. It arises from the anterior tip of the lateral malleolus and travels antero-medially, to insert on the lateral side of the talar neck. Its main function is to resist inversion and plantarflexion.

Fig 1.
Illustration of the lateral ankle ligament complex.

Lateral ankle injuries account for 10% of ED visits nationwide, and can be attributed to 15% (1/10,000) of athletic injuries. The most common patient is males (2.5:1, M:F), 27 years old. In approximately 85% of sprained ankles involve the lateral ligament complex. 65% of the lateral ankle ligament injuries involve an isolated ATFL injury. In 20%, both the ATFL and the calcaneofibular ligament (CFL) are involved. Injuries of the posterior talofibular ligament (PTFL) are rare (5%), and are usually associated by severe dislocation of the ankle joint. With ATFL ligament tears, there is usually a degree of subtalar joint injury. Avulsion injuries of the fibular occur 14% of the time with ATFL injuries.

The majority of patients who injury the ATFL ligament recall an inversion/plantarflexion type injury (fig 2). Individuals usually present to the ED or PCPs office with chief concern of edema, pain and inability to place full weight on the injured ankle. They usually have edema, and ecchymosis may be present (fig 3). A good history is paramount in performing a detailed physical examination, and comparing it to the unaffected contralateral limb. There is usually tenderness with palpation in the area of the sinus tarsi.

Fig 2.
Illustration depicting an inversion/plantarflexion injury.

Fig 3.
Patient picture illustrating ecchymosis in the lateral inferior aspect of the ankle. Additionally, notice the edema the area of the sinus tarsi.

In office testing of the ATFL ligament is relatively easy, however, one must be cautious with the results. The two standard in office testing modalities are the anterior drawer test (ADT) and talar tilt test (TTT). The anterior draw test is accomplished by plantar flexing the ankle 10 degrees stabilizing the anterior distal tibia with one hand and cupping the posterior calcaneus with the other (fig 4A). As the tibia is stabilized, the foot is attempted to be moved forward. Measurements of greater than 3mm when compared to the contralateral limb, on a lateral view, is considered to be pathologic (Fig 4C). The talar tilt test is performed with the patient sitting and the ankle plantar flexed 10-20 degrees (fig 5). As with the ADT, the tibia is stabilized and the ankle is inverted. When compared to the contralateral limb, 5-10 degree increase is indicative of an ATFL tear (fig 5C). Additionally, an increase in 15-30 degrees the ATFL and CFL are torn, greater than 30 degrees ATFL, CFL and PTFL are most probably torn. The one caveat is that because pain and edema are present, these stress tests may be inconclusive secondary to guarding.

Fig 4A.
Picture depicting anterior drawer test.

Fig 4B.
Normal ankle mortise

Fig 4C.
Positive anterior drawer test.

Fig 5A.
Picture depicting the Talar tilt test.

Fig 5B.
Radiographic evidence of a normal mortise.

Fig 5C.
A positive talar tilt test.

Non-invasive testing is an important part in determining whether a tear of the ATFL ligament exists. Magnetic resonance imaging (MRI) (fig 6) is a time tested method of determining soft tissue injuries. Park et al (2012) reported that MRI had a sensitivity and specificity of 75% and 86% for complete ATFL tears, and a sensitivity and specificity of 75% and 78% for partial tears. With the soaring cost to an individual for their deductible, a reliable, cost-effective modality for ATFL radiographic analysis is available. Ultrasound has long been in use for diagnosing soft tissue abnormalities and in aiding in invasive procedures. With the right sonographic personnel, Hua et al. (2012) reported a sensitivity and specificity of 97.7 and 92.3 in determining ATFL tears from intact ligaments (fig 7A and 7B). The practitioner however, should be aware of a phenomenon known as pseudo-band formation. In 2013, Khan et al. described an anomaly where the torn ligament fills in with inhomogeneous scar and inflammatory tissue. This can be mistaken for an intact tear on MRI and US. However, this pseudo-band is usually lax, and can be thicker in comparison to the normal ligament. Moreover, the pseudo-bands margins are usually blurred and irregular.

Fig 6A.
illustrates a nomal, intact ATFL ligament on MRI

Fig 6B.
Demonstrates at torn ATFL ligament on MRI.

Fig 7A.
Illustrates a torn right (RT) ATFL ligament

Fig 7B.
Illustrates an intact ligament

Primary repair of the ATFL is relatively simple procedure. Again, we are only speaking of primary repair of a partially or fully torn ATFL ligament only. Meaning, that the calcaneo-fibular and posterior talo-fibular ligament is intact. An oblique or curvilinear incision is made in the area of the sinus tarsi (fig 8). Blunt dissection is then performed with care not to damage the sural nerve. The ankle capsule will be encountered with a white coloration. One usually can see a thickening of the ankle capsule, representing the ATFL. A small tear can sometimes be visualized in the ankle capsule. Once the capsule is identified, an incision is made in the ankle capsule, in line with the skin incision (fig 9). Once the appropriate ankle capsular incision is made joint fluid is usually encountered. After the ankle capsule is incised a “vest over pants” repair is performed (fig 10). This is best done with the foot placed in slight valgus and dorsiflexed. Performing the repair in this manner will allow the surgeon to place tension on the repair to reconstruct the new ATFL ligament. Varying absorbable and non-absorbable sutures can be utilized for repair. I prefer Arthrex 2-0 Fiberwire, in which I use two figure of eight sutures. The surgeon can then assess the laxity and tightness of the ligament intra-operatively with resistance to PF and inversion. One must also consider that once weight-bearing is initiated, the soft tissues will elongate to reach an appropriate tension. The skin is then sutured, and a soft dressing applied, followed by a below-the-knee (BKC) cast with the foot slightly everted and dorsiflexed.

Fig 8.
Illustrates the incision that can be utilized for primary repair of the ATFL ligament.

Fig 9.
Illustrates incision into the ankle joint in the area of the ATFL allowing proper primary ATFL repair.

Fig 10A.
Depicts the initial suture in the distal capsule

Fig 10B.
Depicts suture in the proximal portion of the ankle capsule. Purse stringing the two sutures with the foot dorsiflexed and slightly everted produces the appropriate position for proper ATFL repair tension.

Aftercare consists of non-weightbearing for 2 weeks with the initial cast, followed by 2 weeks in a BKC with foot 90 degrees to leg (no eversion or dorsiflexion). Following 4 weeks of NWB in a cast, the patient can be progressed to partial weight bearing in an Aircast type immobilizer for 2 weeks, then two weeks of full weight-bearing in an Aircast type immobilizer. Shoe gear can be then initiated to toleration. AT this point in time, the patient should have minimal edema and discuss increasing activities to toleration. An over-the-counter ankle brace can be utilized for the initial 7-10 days in shoe gear to insure stability.

In short, ATFL ligament tears are a quite commonly missed injury that is seen in the ED and PCP office. If a patient has a history of an identifiable ankle injury, ultrasound is an acceptable, cost-effective modality for determining if a tear, full or partial, is present. If US is inconclusive, MRI may need to be performed. Once a tear is determined, primary repair of the ATFL is a fairly easy procedure that should allow the patient to regain their normal activities.