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Radiofrequency thermal effects on the human meniscus. An in vitro study of systems with monopolar and bipolar
C Thomas Vangsness1, John D Polousky, Andrew B Parkinson
1Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
Background:
No data exist on the cutting efficiency of monopolar versus bipolar radiofrequency energy application systems on human meniscal tissue.
Purpose:
To compare the effects of monopolar and bipolar thermal energy systems on human meniscal tissue.
Study Design:
Controlled laboratory study.
Methods:
Fresh-frozen menisci were cut in cross-section into 180 pie-shaped specimens. A specially designed jig was used to consistently apply radiofrequency energy to the tissue under a constant 30-g force. Three different systems were tested at the low, middle, and high ranges, with application times of 1 and 3 seconds. Thermal effects were measured by image analysis microscopy.
Results:
No significant differences in thermal effects were found with respect to energy output for each system. Both the individual system tested and the application time had statistically significant effects on thermal damage, with the individual system tested having a greater effect. The mean depths of thermal change produced by the Mitek (bipolar) device were 564 and 648 microm at 1 and 3 seconds applications, respectively. The Arthrocare device (bipolar) produced depths of 1444 and 1697 microm at 1 and 3 seconds. The Oratec device (monopolar) produced depths of 895 and 1057 microm, respectively.
Conclusions:
A differential thermal effect was created in the meniscal tissue by three commercially available radiofrequency systems. Within the parameters of the experiment, all three systems limited thermal damage to a depth of less than 2 mm. The results appeared to depend more on the particular system used, not whether it had monopolar or bipolar electrodes.
Clinical Relevance:
These data imply reasonably safe (less than 2 mm) thermal changes in the meniscus after radiofrequency energy application from these three systems.