Evaluation of the Intact Anterior Talofibular and Calcaneofibular Ligaments, Injuries, and Repairs With and Without Augmentation: A Biomechanical Robotic Study

Abstract

Background: Acute ankle sprains are common injuries. The anterior talofibular (ATFL) and calcaneofibular ligaments (CFL) are the most injured lateral structures. However, controversy exists on the optimal surgical treatment when the injury is both acute and severe or becomes chronic and unstable. Studies have evaluated the biomechanics of these ligaments, but no studies have robotically evaluated injury effects and surgical treatment of ATFL or ATFL and CFL injuries. Purpose: To quantitatively evaluate biomechanical effects of ATFL and CFL lesions, ATFL repair, ATFL and CFL repair, and augmentation of ATFL on ankle stability. Study Design: Controlled laboratory study. Methods: Ten nonpaired cadaveric ankles were tested using a 6 degrees of freedom robot. Each ankle underwent testing in the following states sequentially: (1) intact, (2) ATFL cut, (3) CFL cut, (4) ATFL repair + CFL cut, (5) ATFL repair + CFL repair, and (6) ATFL repair with augmentation with suture tape + CFL repair. Testing included 88 N anterior drawer and 5 N·m varus talar tilt tests at 0° and 30° of plantarflexion, and 88 N Cotton test at 0° of plantarflexion. Results: After all surgical treatments ankles still had increased laxity compared with intact state testing, except after augmented ATFL repair + CFL repair in anterior drawer testing at 30° of plantarflexion ( P = .393). Sectioning the CFL caused a significant increase in talar tilt compared with the ATFL cut state at 0° ( P < .001) and 30° of plantarflexion ( P < .001), but no increase in anterior drawer or Cotton tests. Conclusion: Complete native stability may not be attainable at time zero repair with the tested treatments. The option that best returned stability in anterior translation was augmented ATFL repair with nonaugmented CFL repair. The importance of the CFL as a primary ligamentous stabilizer for talar tilt was confirmed. Clinical Relevance: Evaluating lateral ankle stability and treatment with a 6 degrees of freedom robot should help delineate optimal treatment options. Findings in this study show that none of the repair methods at time zero restored kinematics to the intact state. Of the tested states, the augmented ATFL repair with CFL repair was the best option for controlling anterior translation at time zero. The importance of addressing the CFL to correct talar tilt instability was suggested as was the importance of a period of immobilization before beginning protected rehabilitation. The benefit of ATFL repair augmentation with suture tape is in limiting the postoperative motion in an anterior drawer motion to just 0.5 to 1 mm, but there was no significant improvement to talar tilt even with CFL repair, suggesting that further consideration should be given to CFL augmentation in future studies.