Osteoid osteoma in an ex vivo animal model: temperature changes in surrounding soft tissue during CT-guided radiofrequency ablation.

Abstract

To assess temperature changes in the soft tissue surrounding bone during radiofrequency (RF) ablation of osteoid osteoma in an ex vivo animal model. Intracortical cavities were created in fresh bovine long bone specimens obtained from a slaughterhouse as models for osteoid osteoma. Three groups of three specimens each were defined according to the thickness (1, 3, and 5 mm) of the cortical bone lamella separating the nidus from the periosteum. Three thermocouples were applied to the soft tissue surrounding the bone in defined distances (0, 5, and 10 mm) from the periosteum. Before RF ablation, the thickness of the cortical bone lamella was documented at computed tomography. Specimens were heated in a 37 degrees C basin. As soon as the measured temperature in the cavity of the specimen reached 35 degrees C, RF ablation was performed for 400 seconds, with a target temperature of 95 degrees C. During RF ablation, continuous measurements were performed simultaneously with digital thermometers. No simulation of vessel perfusion was used. The effect of the thickness of residual osseous lamella and the effect of the distance between the thermocouple and the periosteum were tested with an analysis of variance. Post hoc Bonferroni tests were performed. Mean maximum temperatures of 69.1 degrees, 51.3 degrees, and 42.5 degrees C for 1-mm lamella; 59.2 degrees, 46.5 degrees, and 41.1 degrees C for 3-mm lamella; and 50.6 degrees, 44.8 degrees, and 40.0 degrees C for 5-mm lamella were measured 0, 5, and 10 mm, respectively, from the periosteum. Significant temperature differences were shown with analysis of variance and post hoc tests for the three groups of bone lamella thickness and distance (P < .001). In the model of osteoid osteoma, the surrounding temperature (soft tissue) during RF ablation was shown to depend on the thickness of the cortical bone lamella and the distance from the periosteum.