The Effect of Corticosteroid on Infraspinatous Tendon Insertion Sites in a Rabbit Model

Abstract

To evaluate the effects of corticosteroid on tendon insertion sites, we used corticoteroids-administrated rabbits and evaluated biomechanical and biochemical characteristics of the insertion of the infraspinatus tendon. Twenty-one abult New Zealand White Rabbits were divided into two groups: 9rabbits were with Prednisone 0.150mg/kg subcutaneously daily for 14 weeks; 12 for untreated controls. All of them were sacrifficed at 14 weeks. The bone mineral density (BMD) was measured by DEXA. The specimens were tested for failure load, failure mode, and stiffness of the tendon-bone construct. The BMD was significantly lower in the steroid-administrated group (p<0.001). Two failure modes occurred-failure at the insertion/due to a fracture. There was no significant correlation between BMD and failure load or stiffness. Although not statistically significant, the average BMD tended to be lower in those that failed as fracture and the steroid-administrated specimens tended to fail by fracture with elevated of the tendon-bone construct. There was no significant difference in either stable or reducible collagen cross-link content between the two groups, although there was a tendency for maturation of cross-links in the steroid treated group. After 14 weeks of the abministration, corticosteroids affected bony density and strength, which is more obvious than the effect on the tendon and its insertion.