Objectives-To investigate the eVects 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; stiVness, 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. (Ann Rheum Dis 2001;60:395-398) Rheumatoid arthritis (RA) is a chronic systemic disease. The knee joints of patients with RA are commonly aVected by ligamentous laxity.1-5 Although the instability is partly due to destruction of cartilage and bone in severely aVected knees, knee stability is mainly provided by the ligaments, which are important components of the mechanical functioning of the knee. It is also known that laxity or instability may contribute to the development and progression of degeneration and attrition of the articular cartilage.6-8 However, little is known about changes in the tensile properties of ligaments in RA.Collagen induced arthritis (CIA) is a well known disease model for RA. CIA resembles RA in a number of pathological, histological, and immunological aspects.9-11 Features of CIA include chronic synovitis, including inflammatory cell infiltration, pannus formation, destruction of cartilage, and bone erosion.In this study we aimed at clarifying the changes in tensile properties and histology occurring in the anterior cruciate ligament (ACL) of rats with CIA.
Materials and methods
ANIMALSFemale Sprague-Dawley rats, 4 weeks of age, were obtained from Shimizu Laboratory Supply Co (Kyoto, Japan) and acclimatised for four weeks under standard laboratory conditions. All rats were 8 weeks old at the beginning of the study. During the experimental period, tap water and commercially available food (CE-2, CLEA Japan Inc, Tokyo; calcium content 1.18 g/100 g; phosphorus content 1.09 g/100 g; vitamin D 3 content 250 10 U/100 g) were given freely. The lighting duration in the breeding room was 12 hours (7 00 am to 7 00 pm). The room temperature was 24°C. The experiment was approved by the Committee of Laboratory Animals, Faculty of Medicine, Tottori University.EXPERIMENTAL DESIGN Twenty rats were categorised by body weight into two groups of 10 animals each. In the first group (CIA group), weighing 141.0 (SD 9.95) g, arthritis was induced. The other group (control group), weighing...
