Effect of injected versus iontophoretic corticosteroid on the rabbit tendon

Background. The etiologic role of corticosteroid therapy in tendon rupture is controversial. This study compared the effects of injected versus iontop horetically delivered corticosteroid on the normal rabbit Achilles tendon. Methods. Rabbits were divided into three treatment groups: (1) corticostero id injections, (2) iontophoretically delivered corticosteroid, and (3) no t reatment. One tendon of each rabbit in the treatment groups was treated wit h either drug injection or iontophoresis; the tendon of the other leg serve d as a control. Some tendons were used for testing elastic modulus, ultimat e load, and ultimate stress, while the remaining tendons were evaluated his tologically. Results, Injections of either corticosteroid or saline into the tendon shea th resulted in short-term changes in tendon biomechanical characteristics a nd somewhat higher histologic severity scores; however, iontophoretic deliv ery of corticosteroid or saline did not affect either significantly. Conclusions. Iontophoresis using sterile water or corticosteroid resulted i n minimal or no biochemical and histologic changes in the tendon compared w ith injection of either substance. The method of corticosteroid delivery ma ) be as important as the actual drug effects on the biomechanical and histo logic properties of tendons.