The thermal field of radiofrequency probes at chondroplasty settings

The purpose of this experimental study was to evaluate the thermal field produced with monopolar and bipolar radiofrequency probes located at increasing heights from the target treatment site.

Experimental study.

Two bipolar (ACD-50, ArthroCare, Sunnyvale, CA; VAPR-TC, Mitec Surgical Products, Westwood, MA) and one monopolar (Vulcan TAC-C II, Oratec Interventions, Menlo Park, CA) radiofrequency probes were placed in a screw-driven stage that allowed for 0.25-mm incremental height-position changes. ArthroCare ACD-50 was evaluated at settings 2 and 8. The Mitek VAPR-TC was evaluated at setting 65 degrees C and V2-20 desiccation mode. The Oratec Vulcan TAC-C II system was evaluated at preset 2, power 15, set temperature 70 degrees C. The RF-probes were evaluated at variable distances from 0 to 2 mm. A fluoroptic thermometer was used to evaluate the temperatures within a room temperature 0.9% normal saline arthroscopic simulation chamber.

The ACD-50 setting 2 at 0 mm was 89.1 degrees C; at 0.5 mm, 71.2 degrees C; and at 2 mm it was 37.3 degrees C. The ACD-50 setting 8 at 0 mm was 87.3 degrees C; at 0.5 mm, 42.5 degrees C; and at 2 mm, 33.6 degrees C. The Mitek VAPR-TC at 0 mm was 53.1 degrees C; at 0.5 mm, 42.5 degrees C; and at 2 mm, 26.8 degrees C. The Oratec Vulcan at 0 mm was 73.9 degrees C; at 0.5 mm, 60.3 degrees C; and at 2 mm, 29.0 degrees C. Each of these radiofrequency systems produced characteristic thermal fields at these settings.

The temperature decreases with increasing distance characteristically for each radiofrequency probe. This is clinically important because altering radiofrequency probe location may cause large variations in articular cartilage thermal exposure.