Background: Chronic degeneration of the zygapophyseal joints in the cervical or lumbar spine
are common causes of axial back pain. Radiofrequency (RF) ablation is a treatment modality in
the denervation of facet joint–related pain. Although multiple factors have been theorized to
contribute to the size of the optimal RF lesion, the addition of hypertonic saline solution has been
posited to create larger RF lesion sizes.
Objectives: This study compares lesion of 20-gauge RF monopolar probe using 2% lidocaine,
0.9% normal saline solution, and 3% saline solution administered through the RF needle prior to
ablation, with subsequent lesion sizes recorded.
Study Design: Randomized, double-blinded, ex vivo study using clinically relevant conditions.
Setting: Procedural laboratory in an academic institution.
Methods: RF ablation lesions were reproduced in room temperature (21°C ± 2°C) chicken breast
specimens with 20-gauge monopolar RF probes inserted. RF was applied for 90 seconds at 80°C
after injection of 1 mL of either 2% lidocaine, 2% lidocaine and 0.9% normal saline solution in a
1:1 ratio, or 2% lidocaine and 3% saline solution in a 1:1 ratio. Tissues were dissected, measured,
and ellipsoid volumes of burn calculated. Homogeneity of variances was assessed via the Bartlett’s
test, and heteroskedasticity with the studentized Breusch-Pagan test. One-way analysis of variance
(ANOVA) (α of 0.05) was used to evaluate statistical significance between volume means across
groups. When the null hypothesis of no difference in burn volume between samples could not be
rejected, a predefined equivalence volume of ± 0.05 cm3
was used with Welch’s 2 one-sided t-tests
(TOST) with a Bonferroni adjusted α of 0.0167 to evaluate for null acceptance.
Results: The mean lesion volume for monopolar RF with 1 mL 2% lidocaine was 0.16 cm3
.
Monopolar RF with 1 mL 2% lidocaine + 0.9% normal saline solution had a mean lesion volume of
0.15 cm3
, and treatment with 1 mL 2% lidocaine + 3% saline solution measured 0.17 cm3
. ANOVA
failed to reject the null, and TOST accepted as equivalent all 3 comparisons.
Limitations: In vivo anatomy and physiology of a human organism was not used for this study.
Samples were not warmed to physiologic temperature. Randomization resulted in slightly unequal
sample sizes, although all groups were of sufficient size that the central limit theorem should apply.
Conclusions: Three commonly used solutions were found to have equivalent lesion sizes from
monopolar probe RF ablation.
Key words: Radiofrequency, ablation, lesion shape, lesion size, monopolar RF, hypertonic saline
solution
Comparison of Wet Radiofrequency Ablation with Dry Radiofrequency Ablation and Radiofrequency Ablation Using Hypertonic Saline Preinjection: Ex Vivo Bovine Liver
