Tensile properties of rat anterior cruciate ligament in collagen induced arthritis

Abstract

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.

Figure 1

Changes in hind foot oedema. Each value is the mean and SEM. Open symbols represent control rats; closed symbols represent rats with collagen induced arthritis.

Figure 2

Light micrographs of femoral insertion sites of the anterior cruciate ligament (ACL) (haematoxylin and eosin). (A) Group with collagen induced arthritis (×100). Photomicrograph shows bone resorption around the bone-pannus at the peripheral margins of the ligament insertion site and the enlarged mineralised fibrocartilage zone. (B) Enlarged vascular foramina with inflammatory cell infiltration in cortical bone beneath the ACL insertion is shown (×200). (C) Control group (×100).