The purpose of this study was to determine operating parameters for joint fluid lavage using radiofrequency (RF) in maintaining intra-articular temperatures ≤50°C in the hip joint and to then quantify the influence of flow rate on maintaining safe intra-articular temperatures.
Fiberoptic intra-articular thermometers at radial distance intervals of 1, 2, 5, and 10 mm, spanning cross-sectional areas of 3.14, 12.56, 78.5, and 314.1 mm(2), respectively, from the RF probe were used in 3 human hip cadaveric specimens at room temperature, with 9 trials per variable, using a 3-portal technique with a capsule release. Using a new Dyonics RF System continuously at the superior capsulolabral junction for 90 seconds, continuous temperatures were recorded at 50 mm Hg inflow and variable outflow intervals: no flow and 5, 15, and 30 seconds. Lavages were 1 second in duration on suction. Statistical comparison was through multivariate regression analysis and a logistic model.
Temperatures reached ≥50°C at 5-mm radial distance from the probe in all but the 5-second pulse lavage group. Elevated temperatures were reached within 1 to 2 seconds locally (1- to 2-mm radial distance) and at a radial distance of 5 mm in the 15-, 30-, and 0-second lavage groups. Logistic regression revealed a reduction in the odds that temperatures ≥50°C will occur as flow frequency increases every 30 (odds ratio = 0.68, P = .086); 15 (odds ratio = -1.22, P = .0067); and 5 (odds ratio = -4.26, P < .0001) seconds.
Increasing-interval pulsed irrigation is effective in maintaining intra-articular temperature profiles below 50°C during use of continuous RF ablation. Five-second-interval pulsed lavage is the longest flow interval identified during which fluid 5 mm radially from the RF device never reached temperatures >50°C.
Clinical guidelines for using the RF ablation include: meticulous technique, intermittent use, good inflow and outflow, and pulsed lavage at frequent intervals.