Abstract
Background
The effect of corticosteroids on tendon properties is poorly understood, and current data are insufficient and conflicting. The objective of this study was to evaluate the effects of corticosteroids injection on intact and injured rotator cuff (RC) through biomechanical and radiographic analyses in a rat model.
Methods
70 rats were assigned to seven groups:1)control - saline injection;2) no tear + single methylprednisolone acetate (MTA) injection; 3) no tear + triple MTA injection; 4) tear + single saline injection; 5) tear + single MTA injection; 6) tear+ triple saline injections; 7) tear+ triple MTA injections. Triple injections were repeated once a week. Following unilateral supraspinatus (SSP) injuries, MTA was injected subacromialy. Rats were sacrificed 1 week after last injection. Shoulders were harvested, grossly inspected, SSP was evaluated biomechanically. Bone density at the tendon insertion site on the greater tuberosity (GT) were assessed with micro-computed tomography (CT).
Results
Exposure of the intact RC to the triple MTA injection resulted in significant decrease in maximal load and stiffness as compared to control group (p<0.05). In the injured tendons, at three week, steroids treated group presented with a significantly lower maximal load compared to the saline treated rats (p<0.01). Stiffness was slightly lower in the steroids treated group at three weeks (p=0.1). Micro-CT analysis showed significantly lower GT volume fraction and connectivity density in undamaged rats following triple MTA injection.
Conclusions
Repeated dose of corticosteroids significantly weakens rat RC. Repeated MTA injections negatively affect bone quality and may deteriorate tendon to bone insertion site. However, data retrieved from animals must be scrupulously analysed prior to extrapolation to humans. Despite the limitations, our results clearly show a significant detrimental effect of corticosteroid exposure on the injured rat RC tendon biomechanics. These effects should be well thought-out against any potential benefit prior to administering a subacromial corticosteroid injection.
