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

peer reviewedAbstract 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; CF