Summary

Objective: To determine the short- and long-term changes in the biomechanical properties and metabolic activity of articular cartilage following the remote application of bipolar radiofrequency (bRF) and monopolar radiofrequency (mRF) energy within the rabbit stifle joint. Methods: The rabbits were randomly assigned to either Group-1 (normal rabbit food), or they were assigned to Group-2 (2% Cosequin® in the diet). Each rabbit underwent bilateral stifle arthroscopy with either bRF or mRF applied to the infrapatellar fat pad for 45 seconds. Cartilage samples were collected at zero, four, and 14 weeks after surgery. Data were analyzed with a mixed model analysis of variance (ANOVA) for chondrocyte death, amount of GAG synthesis, and the equilibrium compressive modulus. Results: A significant increase in histological damage was noted at weeks four and 14 compared to week zero. Most of the chondrocyte death noted with confocal laser microscopy (49 of 56 samples) was noted in the superficial region (outer 25%) of the articular cartilage. GAG synthesis was not significantly different between groups or devices at any time point. A significant difference was not noted in equilibrium compressive modulus throughout the study. Conclusions: Remote application of bRF and mRF energy lead to immediate chondrocyte death. Most of the damage was superficial hence the metabolic activity and biomechanical properties of the extracellular matrix were maintained throughout this study. Treatment with Cosequin did not prevent superficial chondrocyte death caused by the application of radiofrequency (RF) energy with in the joint.