Anterior Talo-Fibular Ligament (ATFL)

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Description

The Anterior Talo-Fibular Ligament (ATFL) is one of three ligaments that make up to Lateral Collateral Ligament of the ankle. The ATFL is a short ligament that widens slightly from top to bottom.

Attachments

The anterior talofibular ligament originates from the anterior edge of the lateral malleolus of the fibula and attaches to the neck of the talus, in front of the lateral malleolar facet.

Function

The function of the ATFL is to resist inversion and plantar flexion of the ankle joint. Injury to the ATFL usually occurs when the athlete's center of gravity is shifted over the lateral border of the weightbearing leg, causing the ankle to roll inward at a high velocity. The ATFL is the weakest of the lateral collateral ligaments and therefore the first to be injured.

Mechanisms of injury may include landing awkwardly on an opponent's foot, catching the outer aspect of the foot on the ground terrain, or a slide tackle that contacts the inside of the opponent's weightbearing leg.

Assessment

When a patient presents with a possible ATFL injury, a full physical evaluation should be performed.

1. Observation: Observe for gross abnormalities, edema, ecchymosis, neurovascular assessment,
2. Palpation: Palpate for areas of tenderness over the ATFL and other lateral collateral ligaments. Check the dorsal pedal pulse, capillary refill, and sensation to light touch. Measure edema by using a tape measure to make a figure-8 measurement that encompasses the medial malleolus, lateral malleolus, navicular, and base of the fifth metatarsal. The following Ottawa guidelines should be used to determine if radiographs are necessary: palpation that reveals tenderness over the medial malleolus, lateral malleolus, navicular, and/or base of the fifth metatarsal; an inability to bear weight immediately following injury or during the clinical evaluation; or tenderness that extends 6 cm superiorly from the tip of either malleolus, not over the ATFL.1,26,38Radiographs should be performed immediately if gross abnormalities are visualized. Standard radiographic views include anterior to posterior, lateral, and ankle mortise. Even if radiographs are inconclusive, a Salter-Harris type 1 fracture should be considered in a skeletally immature patient if palpation elicits tenderness over the distal tibia or fibula growth-plates.
3. Range of Motion: Goniometric measurements should be taken of active and passive ranges of motion bilaterally.
4. Special Tests:

• Anterior drawer test: Stabilizing the tibia and fibula, the foot is held in 20° of plantar flexion while the talus is drawn forward in the ankle mortise. This tests the integrity of the ATFL and anterior joint capsule. A positive test result would be greater than 5 mm of anterior motion of the STJ as compared with the noninjured ankle, and an audible clunk may be elicited. If the ankle is inverted while conducting the anterior drawer test, it also evaluates the integrity of the CFL.
• Talar tilt test: The ankle is held in anatomical position, and the talus is tilted into adduction and abduction. This primarily tests the integrity of the CFL when the foot is in a neutral position; when the test is performed with plantar flexion, it also evaluates the integrity of the ATFL. A positive test result would be 5° to 10° of increased inversion as compared with the noninjured ankle and would be indicative of a tear of the CFL.
• External rotation test: Manual passive external rotation of the foot and ankle in a neutral or slightly dorsiflexed position would widen the ankle mortise. Pain over the distal syndesmosis is positive for a syndesmotic injury.
• Tibia/fibula squeeze test: Result is positive for a syndesmotic sprain if compression of the tibia and fibula in the midcalf region produces pain over the distal syndesmosis.
• Stabilization test: Tape is applied around the distal syndesmotic region for support. A positive test result for syndesmotic injury would be reduced pain over the distal syndesmosis during ambulation or when performing a heel raise.

These orthopedic tests should be conducted bilaterally. During the initial stages of injury, the findings of these examination tools may be limited because of pain, swelling, and spasm. The anterior drawer and the talar tilt test are found to have a markedly increased sensitivity when performed 4 to 5 days after injury.

Examination findings of a lateral ankle sprain may include the following:

• Swelling observed distal to the lateral malleolus of the ankle that may extend to the foot if the lateral capsule is torn.
• Tenderness palpated over the ATFL and, in more severe cases, the CFL.
• The anterior drawer and the talar tilt test may reveal joint laxity due to tearing of the ATFL and/or the CFL ligament.
• Stress radiographs may reveal excessive anterior translation of the talus or inversion of the talus.

Lateral ankle sprains are based on a grade 1 to 3 classification.

• A grade 1 ankle sprain usually entails microscopic tearing of the ATFL. Symptoms may include minimal swelling and point tenderness directly over the ATFL; however, there is no instability, and the athlete can ambulate with little or no pain.
• A grade 2 ankle sprain involves microscopic tearing of a larger cross-sectional portion of the ATFL. Symptoms may include a broader region of point tenderness over the lateral aspect of the ankle, a painful limp if able to ambulate, and bruising and localized swelling due to tearing of the anterior joint capsule, ATFL, and surrounding soft tissue structures.
• A grade 3 ankle sprain entails a complete rupture of the ATFL and may also involve microscopic or complete failure of the CFL. The posterior talofibular ligament is rarely injured during inversion ankle sprains. Symptoms may include diffuse swelling that obliterates the margins of the Achilles tendon, inability to ambulate, and tenderness on the lateral and medial aspects of the ankle joint.