Native anterior talo-fibular ligament tensile characteristics compared to allograft, suture tape, and copolymer augmentation elements: A biomechanical study

Abstract

Surgical augmentation methods have been introduced to the Modified Broström (MB) technique to support native anterior talo-fibular ligament (ATFL) healing and function. This study aimed to investigate the isolated biomechanical performance of common MB augmentation elements, including allograft, suture tape, and copolymer, compared to native ATFL. Six cadaveric feet were dissected, isolating the ATFL from all surrounding soft tissue. The fibula and talus were clamped on the testing frame so that the ligament was in line with the load cell. Six samples per augment group were fixed on a test frame with a gauge length of 20 mm to replicate ATFL length. All samples were pulled to failure at 305 mm/min. Biomechanical outcomes included stiffness, elongation, and ultimate load. Mean ± standard deviation was reported. Stiffness was highest for suture tape (246.4 ± 52.1N/mm), followed by allograft (114.2 ± 26.2 N/mm), native ATFL (78.6 ± 31.8 N/mm), and copolymer (9.4 ± 2.9 N/mm). Significant differences in stiffness were observed between all groups except when comparing ATFL stiffness to allograft (P = 0.086). Copolymer resulted in significantly larger elongation at ultimate load compared to native ATFL, suture tape, and allograft (P < 0.001). Elongation at ultimate failure was highest for copolymer (30.0 ± 8.7 mm) and significantly greater than all other groups (P < 0.001). Ultimate load was highest for suture tape (544.1 ± 59.7 N), followed by native ATFL (338.5 ± 63.7 N), allograft (308.3 ± 98.5 N) and copolymer (146.7 ± 8.9 N). Suture tape ultimate load was significantly greater than copolymer (P < 0.001). Isolated biomechanical data of augment materials can be utilized by foot and ankle surgeons when considering appropriate ligament augmentation options.