Determination of Factors Influencing Tissue Effect of Thermal Chondroplasty: An Ex Vivo Investigation

Purpose: Scientific investigation of thermal chondroplasty using radiofrequency energy (RFE) is confounded by multiple factors associated with the technique. Our purpose was to determine the relative importance of the following factors on tissue effect (depth of tissue debridement plus depth of underlying cell death) of thermal chondroplasty: probe design, generator power setting, speed, force, and number of passes of the probe over treated tissue. We hypothesized the relative importance of these factors would be (from most to least important) power, passes, speed, force, and design. Methods: Bovine patellae were treated using monopolar RFE. Sample size was based on a 2-level, half-factorial design. Low and high extremes of the factors tested were power setting (50 W v 110 W), passes (1 v 5), speed (3 mm/sec v 10 mm/sec), force (0.15 N v and 0.59 N), and probe design (electrode protrusion 25 μm v 125 μm). Samples were incubated with cell viability stain and examined using confocal laser microscopy to determine tissue effect. Data were analyzed using multiple regression. Results: All factors that were tested significantly influenced tissue effect (P < .05). Power setting had the greatest effect, followed by design, speed, passes, and force. The following interactions of factors were also significant: design and force, power and passes. The optimal configuration resulting in least tissue effect was a power setting of 50 W, electrode protrusion of 25 μm, speed of 10 mm/sec, 1 pass, and 0.15 N of applied force during treatment, which resulted in a predicted tissue effect of 99 ± 15 μm. Conclusions: The least tissue effect of thermal chondroplasty was achieved with lower power using a probe with minimal electrode protrusion while performing a rapid, single, lower force pass of the probe over treated tissue. Clinical Relevance: Power and probe design have the greatest influence among the factors tested; selecting these parameters preoperatively could control tissue effect.