The Role of Calcaneofibular Ligament (CFL) Injury in Ankle Instability: Implications for Surgical Management.

Abstract
Background: Acute inversion ankle sprains are among the most common musculoskeletal
injuries. Higher-grade sprains, including anterior talofibular ligament (ATFL) and
calcaneofibular ligament (CFL) injury, can be particularly challenging. The precise impact of
CFL injury in ankle instability is unclear.
Hypothesis/Purpose: We hypothesized that CFL injury will result in decreased stiffness, peak
torque, and increased talus and calcaneus motion, as well as alter ankle contact mechanics when
compared to the uninjured ankle and the ATFL only injured ankle in a cadaveric model.
Study Design: Controlled Laboratory Study
Methods: Ten matched-pairs of cadaver specimens with a pressure sensor in the ankle joint and
motion trackers on the fibula, talus, and calcaneus were mounted on an Instron with 20° of ankle
plantar flexion and 15° of internal rotation. Intact specimens were axially loaded to body weight,
then underwent inversion along the anatomic axis of the ankle from 0° to 20°. The ATFL and
CFL were sequentially sectioned and underwent inversion testing for each condition. Linear
mixed models (LMMs) were used to determine significance for stiffness, peak torque, peak
pressure, contact area, and inversion angles of the talus and calcaneus, relative to the fibula
across the three conditions.
Results: Stiffness and peak torque did not significantly decrease after sectioning the ATFL, but
decreased significantly after sectioning the CFL. Peak pressures in the tibiotalar joint decreased
and mean contact area increased significantly following CFL release. There was significantly
more inversion of the talus and calcaneus as well as calcaneus medial displacement with weight
bearing inversion after sectioning the CFL.
Conclusions: The CFL contributes considerably to lateral ankle instability. Higher-grade sprains
that include CFL injury result in significant decreases in rotation stiffness, peak torque,
substantial alteration of contact mechanics at the ankle joint, increased inversion of the talus and
calcaneus, and increased medial displacement of the calcaneus.
Clinical Relevance: Repair of the CFL should be considered during lateral ligament
reconstruction when injured, and there may be a role for early repair in high-grade injuries to
avoid intermediate and long-term consequences of a loose or incompetent CFL.
Key Terms: Ankle, Ligaments; Ankle Instability; Ankle Sprain; ATFL; CFL