Effect of steroid injections on the rotator cuff: An experimental study inrats

The aim of this study was to evaluate the effects of repeated steroid injec tions into the subacromial space. Thirty rats were injected either 3 or 5 t imes with triamcinolone in a dosage equivalent to that given to human being s or 3 or 5 times with saline into the subacromial space. One rat received no injection. The supraspinatus and infraspinatus tendons were evaluated ma croscopically and microscopically. Two different staining methods were used on each sample including hematoxylin eosin and Miller's elastin/van Gieson 's solution. After 5 steroid injections, we found focal inflammation, necro sis, and fragmentation of collagen bundles in the tendon in 4 of 7 rats. Th e tendons of the controls showed a normal structure (P < .05). There were n o pathologic changes among the rats that were injected with triamcinolone 3 times. These results show that repeated subacromial injections of triamcin olone may cause damage to the rotator cuff of the rat. This finding may ind icate cautious use of subacromial steroid injections in human beings.