A biomechanical study of human lateral ankle ligaments and autogenous reconstructive grafts

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Abstract
The purpose of this study was to investigate the bio mechanical behavior of human anterior talofibular and calcaneofibular ligaments, as well as peroneus brevis, split peroneus brevis, and toe extensor tendon grafts. This article represents the first published data compar ing the most frequently injured ankle ligaments to the most commonly used autogenous reconstructive grafts. Twenty fresh human ankles provided the bone-liga ment-bone and tendon graft specimens for biomechan ical testing on a Minneapolis Testing System. Protocol consisted of cyclic loading at physiologic deflections, followed by several load-deflection tests at varying velocities, followed by a final extremely rapid load to failure test. The load-deflection data for all ligaments and tendons demonstrated nonlinearity and strain rate dependence. The maximum load to failure for the anterior talofibular ligament was the lowest of all specimens tested, while its strain to failure was the highest. The loads to failure of the peroneus brevis and split peroneus tendons were signficantly greater than the anterior talofibular ligament and approximately equal to the calcaneofibular liga ment. Strains to failure for all tendons were significantly less than ligament strains. The high strain to failure of the anterior talofibular ligament demonstrates its physiologic function of allow ing increased ankle plantar flexion-internal rotation, while its low load to failure shows its propensity for injury. The greater strength of the tendon grafts ex plains the success of most reconstructive procedures in reestablishing stability in chronic ankle sprains; at the same time, the data presented suggest that those surgical procedures sacrificing the entire peroneus brevis tendon are unnecessary. Finally, the greater stiffness of the tendon grafts may cause postoperative decreases in ankle and subtalar motion.