MECHANICAL-PROPERTIES OF THE HUMAN ANTERIOR CRUCIATE LIGAMENT

The aim was to measure the stiffness and strength of the femur-anterio r cruciate ligament-tibia complex tested in a physiological manner wit h a force exerted anteriorly on the tibia, at knee joint flexion angle s of 0 degrees, 10 degrees and 30 degrees and at speeds of 50 and 500 mm/min. Ligaments were preconditioned by cycling five times, with data from the fifth cycle used to determine the stiffness of the ligament in a low-load range. The ligaments were then tested to failure with th e knee at 30 degrees flexion. The specimens were divided into two grou ps, middle-aged (40-60) and old (>60). For each group no statistical d ifference was observed between stiffness of the ligament at different joint flexion angles or speeds. Seven of the 21 specimens in the older age group failed by avulsion at the bone-ligament interface. All the other specimens failed by tears in the substance of the ligament. Ulti mate failure load was found to have a significant correlation with bod yweight. It was 1.6 and 1.3 times bodyweight for the middle-aged and o lder age groups respectively. This study has highlighted the importanc e of identifying different modes of failure, of making corrections for bodyweight and testing in a physiological manner. The results allow a better understanding of the mechanical behaviour of the anterior cruc iate ligament and provide design data for anterior cruciate ligament g rafts and prostheses. Relevance-Our clinical experience indicates that the anterior cruciate ligament is frequently ruptured during uncoordi nated contraction of the quadriceps mechanism. The results of this stu dy, in which the mechanical properties of the anterior cruciate ligame nt have been measured with force exerted anteriorly on the tibia, allo w a more complete understanding of the mechanical behaviour of the ant erior cruciate ligament and provide design data for anterior cruciate ligament grafts and prostheses.