A Radiological and Histological Evaluation of Ionic and Non-Ionic Contrast Agents in Rabbit Knees

Abstract

Non-ionic contrast agents, metrizamide (MET) and iosulamide (IOSUL) and ionic agents, Renografin-60 (RENO-60) and Renografin-60 with epinephrine (RENO-60 + EPI) were evaluated to determine their effectiveness as arthrographic contrast agents. The histological changes in the synovium and joint were determined. To ascertain a radiographic timing sequence, the persistence of diagnostic joint opacification was determined. New Zealand white rabbits were studied in 5 groups of 12 rabbits each: control (saline), and MET, IOSUL, RENO-60 and RENO-60 + EPI. Each agent had an iodine concentration of 280mg/ml. All radiographs were taken using the same radiographic technique at 2, 5, 20, 30 and 60 minutes after injection. Two investigators graded each arthrogram. At least four animals in each group were sacrificed at 24 hours, 7 days and 28 days respectively. Both the contrast injected knee and the opposite control saline injected knee were examined histologically and graded. Histologic evaluation revealed statistically significant (p<0.05) inflammation in the joints injected with MET and RENO-60. The degree of inflammatory change was more pronounced with MET compared to RENO-60. All significant inflammation was noted within the first week after injection. Arthrographic scores judging persistence of diagnostic opacification were highest for IOSUL followed by RENO-60 + EPI, MET and RENO-60 respectively. Scores in all groups were below average at 30 and inadequate at 60 minutes. No statistical difference in degree of opacification existed between contrast agents at any interval. The non-ionic or ionic character of an agent does not affect the diagnostic opacification obtained at arthrography. Short term local inflammatory changes may be produced by either type of agent. These data suggest that one might choose an agent based on the degree of inertness since little difference exists in opacification. Supported by a grant from Sterling-Winthrop Research Institute.