Chondrocyte viability and metabolic activity after treatment of bovine articular cartilage with bipolar radiofrequency: an in vitro study

Abstract

Purpose: Some controversy exists regarding the effects of radiofrequency (RF) probes on articular cartilage. To further elucidate these effects, we examined the chondrocyte viability and metabolic activity after treatment of fresh bovine articular cartilage with bipolar RF probes.

Type of study: In vitro assessment.

Methods: Three fresh bovine knees served as a baseline control for chondrocyte viability, yielding 6 samples (1 from each medial femoral condyle and 1 from each lateral femoral condyle). After the baseline expected chondrocyte viability was determined, 3 additional bovine knees served as the experimental specimens for the study. Under sterile conditions, 2 different bipolar RF probes were used to treat the articular surface in a light contact mode, moving at a linear rate of 3 to 4 mm/s to provide tissue debridement. Full-thickness articular cartilage was then harvested from each of the treatment areas. Six samples per probe were then assessed for chondrocyte viability using fluorescent double-staining followed by confocal microscopy; 6 samples per probe were assessed for metabolic activity using an 35SO4 incorporation assay; and 12 additional untreated samples were obtained to serve as controls for viability (n = 6) and metabolic activity (n = 6).

Results: The depth of chondrocyte death (mean +/- standard deviation) was 109.4 +/- 22.1 microm after treatment with the ACD-50 probe, and was 172.3 +/- 34.3 microm after treatment with the 2.5-mm/90 degrees probe. The 35SO4 uptake (mean +/- standard deviation) was 2584 +/- 1388 cpm/mg dry cartilage for the ACD-50 probe and 1995 +/- 852 cpm/mg of dry cartilage for the 2.5-mm/90 degrees probe. The 35SO4 uptake for the control was 2647 +/- 1380 cpm/mg dry cartilage.

Conclusions: The 2 probes tested created a well-controlled debridement with smooth edges and a defined margin of chondrocyte death that extended approximately 100 to 200 microm deep to the treatment area. There does not appear to be a significant effect on the metabolic activity of the chondrocytes adjacent to the treatment zone, but with the small sample size we lacked sufficient statistical power to definitively determine these effects.

Clinical relevance: The 2 bipolar radiofrequency probes tested created a well-controlled debridement in normal articular cartilage with smooth edges and a defined margin of chondrocyte death that extended approximately 100 to 200 microm into the treatment area.