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Background: There are growing concerns about thermal chondroplasty using radiofrequency energy to treat partial-thickness cartilage defects. However, most studies emphasize effects on chondrocyte viability, and other factors such as mechanical properties are less studied., Hypothesis: Radiofrequency energy may cause significant effects on articular cartilage other than chondrocyte viability., Study Design: Controlled laboratory study., Methods: Human osteoarthritic cartilage samples were obtained from total knee arthroplasty, and monopolar radiofrequency energy was applied using commercially available equipment. Material properties (compressive stiffness, surface roughness, and thickness) just before and after thermal treatment were determined using ultrasound. A series of biochemical analyses were also performed after explant culture of the samples., Results: The cartilage surface became smoother by radiofrequency energy, whereas cartilage stiffness or thickness was not altered significantly. Collagen fibrils, especially in the superficial layers, were converted to denatured form, whereas proteoglycan contents released in the media as well as retained in the tissue remained unchanged. The concentrations of matrix metalloproteinases (MMP-1 and MMP-2) were reduced remarkably., Conclusion: Radiofrequency energy is able to create a smooth cartilage surface and reduce catabolic enzymes at the cost of collagen denaturation and chondrocyte death in the superficial layers. The stiffness of the cartilage is not changed at time zero., Clinical Relevance: Further animal as well as clinical studies will be necessary to fully evaluate the long-term effects of radiofrequency energy.

Background: Previous radiofrequency work has not rigidly controlled energy application to the articular cartilage, giving uncertain results published to date., Hypothesis: At minimal settings, radiofrequency probes cause cell death in measurable areas when applied to human articular cartilage., Study Design: Controlled laboratory study., Methods: Simulating operating room conditions, 5 commercially available radiofrequency probes were attached to a customized jig to standardize a minimal contact pressure of each probe tip to 2.0 g. Keeping all variables the same, probes were placed on specific points of fresh grade II human cartilage with treatment times of 1 and 3 seconds at the manufacturer's recommended settings. Grade III cartilage was also tested with a treatment time of 3 seconds, and grade II cartilage was studied with the probe held 1 mm off the cartilage surface. Cartilage was blindly analyzed by confocal microscopy using a live/dead cell viability assay to determine the extent of cell death., Results: Radiofrequency probes produced significant cellular death in the form of a half-circle into the cartilage to variable depths. For treatment times of 1 and 3 seconds, cell death measurements ranged from 404 to 539 mum and 1034 to 1283 mum, respectively. One probe failed to show any effect, with minimal evidence of cell death or cartilage smoothing. When probes were kept a 1.0-mm distance above the cartilage, no cell death or cartilage smoothing was noted. Radiofrequency treatment of grade III cartilage penetrated to the subchondral bone. There was no statistically significant difference between the damage caused by monopolar and bipolar probes when tested under these rigidly controlled conditions., Conclusion: These results showed significant cellular death at these minimal conditions to the underlying chondrocytes with radiofrequency probes. Surgeons using this technology need to be aware of the power and dangerous potential these probes can have on articular cartilage.

We compared the effects of treatment with bipolar and monopolar radiofrequency energy on 30 osteochondral sections harvested from 22 patients with spontaneously occurring chondromalacia who were undergoing knee arthroplasty. Specimens with chondromalacia grades 2 or 3 were randomly assigned to one of two bipolar or one monopolar treatment groups. All samples were marked and mounted on a jig to allow simulation of an arthroscopic surgical procedure with a flow rate of 100 ml/min of a balanced electrolyte solution at 22 degrees C. Under arthroscopic visualization, the designated area was treated until smooth, and the total treatment time was recorded. There was no difference in patients' ages, chondromalacia grade, or cartilage thickness among groups. Significant chondrocyte death, as determined by cell viability staining with confocal laser microscopy, was observed with each group. The bipolar devices produced significantly greater depths of chondrocyte death (2228 +/- 1003 microm and 2810 +/- 517 microm) than did the monopolar device (737 +/- 391 microm). The bipolar devices caused cell death to subchondral bone significantly more often (13 of 20 specimens) than did the monopolar device (0 of 10 specimens). Caution should be used in treating fibrillated cartilage with radiofrequency energy, particularly with the bipolar devices tested.