Temperature requirements for altering the morphology of osteoarthritic and nonarthritic articular cartilage: in vitro thermal alteration of articular cartilage.

BACKGROUND: Radiofrequency and laser thermal chondroplasty procedures are performed to debride and smooth fibrillated, articular cartilage. HYPOTHESIS: Temperature requirements necessary to achieve morphological change will be lower in fibrillated arthritic cartilage as compared with nonarthritic articular cartilage. STUDY DESIGN: Controlled laboratory study. METHODS: A thermal cell-culture chamber was mounted on a stereoscopic microscope and coordinated with a custom temperature-control program. Nonarthritic and osteoarthritic articular cartilage specimens were sectioned into full-thickness slices. The articular sections were exposed to temperatures incrementally from 37 masculine C to 75 masculine C. Real-time, digital capture microscopy was used to visualize and analyze the morphological changes undergone by the articular cartilage specimens. RESULTS: Arthritic articular cartilage displayed morphological change at 56.5 +/- 1.7 masculine C. Loss of fibrillation was the initial morphological change visualized. Continued thermal exposure caused a shrinkage effect of the entire tissue section that was similar to the change seen in nonarthritic sections. Nonarthritic cartilage displayed morphological change at 60.9 +/- 1.9 masculine C. CONCLUSIONS: Consistent characteristic morphological changes were found at distinct temperatures in osteoarthritic and nonarthritic articular cartilage. CLINICAL RELEVANCE: This information begins to establish the thermal parameters required for morphological change of osteoarthritic articular cartilage.

The thermal field of radiofrequency probes at chondroplasty settings.

PURPOSE: 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. TYPE OF STUDY: Experimental study. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.