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Calcaneofibular Ligament


- Discussion:
    - calcaneofibular ligament is a extra-articular round and cordlike ligament which connnects tip of distal fibula to small tubercle on posterior & lateral aspect of calcaneus;
    - crosses two joints, talocrural and the talocalcaneal;
    - 2 cm long, 5 mm wide, and 3 mm thick;
    - calcaneal attachment of calcaneofibular lig is 13 mm from subtalar joint, & that insertion of anterior talofibular ligament onto talus is 18 mm posterior to subtalar joint;
    - calcaneofibular lig attaches posteriorly on calcaneus to form 133-deg angle w/ fibula when ankle is in neutral dorsiflexion-plantar flexion
    - it is in close contact with medial peroneal sheath, but is not associatted with either the ankle capsule or peroneal tendon sheath;

- Function:
    - it is lax in normal, standing position due to relative valgus orientation of calcaneus;
    - it acts primarily to stabilize sub-talar joint & limit inversion;
    - this ligament is extra-articular but it has an intimate connection to overlying peroneal-tendon sheath;
    - calcaneofiblar ligament may be lax until supination force is applied;
    - greatest strain occurrs when inversion moment is applied w/ ankle in dorsiflexion;
    - because of its unique anatomical orientation, calcaneofibular ligament also has major role in stabilization of subtalar joint;
    - isolated rupture of the calcaneofibular ligament probably does not cause demonstrable ankle laxity;

- Exam:
    - inversion (supination) test;
    - w/ ankle in plantarflexion: evaluates anterior talofibular ligament;
    - in neutral / slight dorisflexion: evaluates calcaneofibular ligament;
    - talar tilt:
            - talar instability is assessed w/ talar tilt test, in which angle formed by tibial plafond & talar dome is measured as inversion force is applied to  hindfoot;
            - talar tilt test is useful for evaluation of combined injury of both anterior talofibular & calcaneofibular ligament;
    - talar tilt to ranges from 0 to 23 degrees in normal ankles, while but normal ankles tend to have < 5 degrees of talar tilt;

- Arthrography:
    - w/ ankle arthrography, contrast medium often fails to enter peroneal sheath, despite operatively proved tears of calcaneofibular ligament;
    - technique of peroneal tenography was developed has proved to be more accurate in the diagnosis of disruption of calcaneofibular ligament;
    - leakage of the dye through a particular ligament or thru the distal tibiofibular syndesmosis will pin point structure torn;
    - performed by inserting 22 gauge needle into the medial side of joint;
    - extra articular dye anterior to the laterala malleolus is always associatted with a rupture of ATFL;
    - dye seen in peroneal sheath usually is caused by rupture of CFL;
    - extension of contrast > 3.5 cm above joint is c/w ligamentous injury;
    - arthrography needs to be performed within 1 week of injury or fibrin clots may seal any capsular tear