Tensile properties of rat anterior cruciate ligament in collagen induced arthritis

Objectives-To investigate the effects of collagen induced arthritis (CIA) on the tensile properties of rat anterior cruciate Ligament (ACL). Methods-The tensile strength, bone mineral density (BMD), and histology of ACL units from rats with CIA were investigated. Results-The tensile strength of the ACL unit was significantly lower in the rats with CIA at 10 weeks after immunisation (ultimate failure load, 74.9% of the control; stiffness, 62.0% of the control). The major mode of failure was femoral avulsion, and the BMD was significantly lower in the rats with CIA. A histological examination of the ligament insertion in rats with CIA showed resorption of the cortical bone beneath the ACL insertion and an enlarged mineralised fibrocartilage zone. Conclusions-These findings indicate that the decrease in tensile strength of ACL units correlated with histological changes in the ligament-bone attachment, such as bone resorption beneath the ligament insertion site and an enlargement of the mineralised fibrocartilage zone.