title: Radiofrequency ablation near the bone-muscle interface alters soft tissue lesion dimensions.
abstract: OBJECTIVE
  Radiofrequency (RF) lesions are safe and effective in the treatment of spine pain; however, models developed to study factors affecting lesion dimensions have been performed in homogeneous media that may not accurately simulate human anatomy and electrophysiology. We present a novel ex vivo porcine model for performing RF lesion studies and report the influence of bone on projection of RF ablation lesions into soft tissue.
  
  
  METHODS
  Radiofrequency lesions were performed in porcine rib specimens using monopolar 18-gauge, 10-mm straight active tip cannula, with a lesion temperature of 80°C for 150 seconds. Ten lesions were performed in pure porcine muscle tissue and abutting porcine rib bone with surrounding muscle. Lesions were exposed with dissection and measured with digital calipers.
  
  
  RESULTS
  Maximal effective lesion radius approximately doubled against the bone compared with the pure muscle group (mean, 5.65 mm [95% CI, 5.43-5.87 mm] vs 2.68 mm [95% CI, 2.55-2.81 mm], P < .0001), although this was seen only in a vertical direction and not horizontally. In addition, the prelesion and postlesion impedance of the bone-muscle interface was consistently higher than the muscle-only interface (mean, 165.6 Ohm [95% CI, 146.6-184.6 Ohm] vs 137.8 Ohm [95% CI, 135.5-140.1 Ohm], P = 0.004; 144.3 Ohm [95% CI, 134.3-154.3 Ohm] vs 124.3 Ohm [95% CI, 119.3-129.3 Ohm], P = 0.001). Other dimensions and estimated volume were not significantly different.
  
  
  CONCLUSIONS
  Bone adjacent to RF lesions alters the surrounding electrophysiological environment causing RF lesions to project further perpendicularly from the needle axis, vertically to bone, than previously expected. This phenomenon should be considered in the future modeling and clinical practice of RF.
authors.affiliation: From the *Department of Anesthesiology, The University of Texas Health Science Center at San Antonio (UTHSCSA), San Antonio; and †Advanced Spine Pain Solutions, Laredo, TX.
authors.forename: Maxim S
authors.initials: MS
authors.lastname: Eckmann
authors.forename: Marte A
authors.initials: MA
authors.lastname: Martinez
authors.forename: Steven
authors.initials: S
authors.lastname: Lindauer
authors.forename: Asif
authors.initials: A
authors.lastname: Khan
authors.forename: Somayaji
authors.initials: S
authors.lastname: Ramamurthy
mesh_terms: D000818:Animals; D001837:Body Weights and Measures / Q000706:statistics & numerical data*; D017115:Catheter Ablation / Q000009:adverse effects*; D006358:Hot Temperature / Q000009:adverse effects*; D023421:Models, Animal; D018482:Muscle, Skeletal / Q000601:surgery*; D012272:Ribs / Q000601:surgery; D013552:Swine