Becker's Spine Review

75 Executive Briefing Effect of the Stryker Venom Cannula and Venom Electrode combination on lesion size and anesthesia delivery during radiofrequency ablation S tryker Instruments, 4100 East Milham Avenue, Kalamazoo, Michigan 49001 Abstract Background and objectives: Stryker's new Venom Cannula and Venom Electrode combination has a larger active-tip surface area than the standard radiofrequency (RF) cannula and electrode com- bination. The objective of this study was to investigate whether radiofrequency ablation using the Venom Cannula and Venom Electrode combination produces larger lesions than the standard RF cannula and electrode combination in ex vivo chicken breasts. The location of fluid propagation was also compared between the Venom Cannula and the standard RF cannula to determine wheth- er the delivery of anesthesia to a targeted lesion zone would differ between the two cannula designs. Methods: Three sets of side-by-side lesions were created with the 20-gauge Venom Cannula and the 20-gauge standard RF cannula (both with 10mm active tips) in ex vivo chicken breasts. Thermal lesions were created with temperature control at 80°C for 90 sec- onds using Stryker's MultiGen® Radiofrequency Generator (Stryker Instruments, Kalamazoo, Michigan). The testing procedure was repeated using the 18-gauge Venom and 18-gauge standard RF cannulae on a separate chicken breast. The length and transverse width of the lesions were measured, and the volume was calculat- ed. The location of fluid propagation was compared between the Venom Cannula and the standard RF cannula after dispensing an aliquot of dyed solution from each cannula onto wetted gauze. Results: On average, the 20-gauge Venom Cannula created a le- sion of 92% greater volume than the 20-gauge standard RF can- nula, and the 18-gauge Venom Cannula created a lesion of 76% greater volume than the 18-gauge standard RF cannula. In the fluid propagation test, the Venom Cannula dispersed the solution more proximal to the center of the exposed tip (i.e., more local to the side port), whereas the standard RF cannula dispersed the solution in a location more distal to the exposed tip. The solution dispersion from the Venom Cannula also provided more adequate coverage of the exposed tip than did the standard RF cannula. Conclusions: The new Venom Cannula and Venom Electrode com- bination created larger radiofrequency lesions than a standard RF cannula of the same gauge size and exposed tip length in ex vivo chicken breasts. When a fluid was dispensed down the Venom Can- nula, the immediate propagation of the fluid was more local to the exposed tip than it was with a standard RF cannula, suggesting that the Venom Cannula may provide more efficient delivery of anes- thesia to a targeted lesion zone, which may lead to greater proce- dural efficiency. Introduction Radiofrequency ablation provides an effective and minimally inva- sive treatment for facet joint pain, particularly in patients who do not respond to conservative treatments and who want a minimally invasive alternative to surgery. 2,3,4 With this procedure, cannulae are carefully inserted percutaneously into the treatment area using fluoroscopic guidance. Electrodes are inserted into the cannulae, and radiofrequency energy is transferred from the active tip of the electrode and needle to the surrounding nerve tissue via direct contact. The radiofrequency energy causes the tissue to heat up and undergo cellular necrosis, and the resulting lesions disrupt the ansmission of pain signals to the brain. 5 Technical challenges exist for the effective use of radiofrequency treatment for spinal pain. Given the small diameter of the target nerves and small area affected by radiofrequency ablation, Cohen and Rathmell 6 have noted the risk of treatment failure in anatom- ically difficult patients or when proper technique is not used. In the lumbar spine, the orientation of the facet joints and nerves fur- ther complicate the positioning of straight needles parallel to the nerves. However, efforts have been made to increase lesion size as a way to ensure that the target nerves are not missed. Provenza- no et al. 7 showed that the injection of various fluids before radiof- requency ablation led to increased lesion sizes in ex vivo chicken breasts. Mulier et al. 8 investigated the influence of inter-electrode istance on lesion size and geometry in ex vivo liver. Stryker has developed a new radiofrequency cannula and elec- trode combination, the Venom Cannula and Venom Electrode, which increases the power output from the radiofrequency gen- erator by increasing the surface area of the active tip. This is achieved by allowing the electrode to come out a side port on the exposed surface of the cannula, so that the new active tip includes both the uninsulated surface of the cannula and the protruding electrode tip. The Venom Cannula and Venom Electrode combi- nation provides an active-tip surface area that is approximately 30% larger than the standard RF cannula and electrode for the 20-gauge size and approximately 22% larger than the standard RF cannula and electrode for the 18-gauge size. In this study, Stryker investigated whether radiofrequency ablation using the Venom Cannula and Venom Electrode combination pro- duces larger lesions than the standard RF cannula and electrode in ex vivo chicken breasts. The location of fluid propagation was also compared between the Venom Cannula and the standard RF can- nula to determine whether the delivery of anesthesia to a targeted lesion zone would differ between the two cannula designs. Methods Thermal dosing test: The power output was compared between the Venom Cannula and standard RF cannula during radiofrequen- cy ablation in ex vivo chicken breasts. The following four cannulae were inserted, with equal spacing between them, into a piece of ex vivo chicken breast at room temperature: (1) 100mm, 20-gauge, 10mm tip Venom Cannula; (2) 100mm, 20-gauge, 10mm tip stan- dard RF cannula; (3) 100mm, 18-gauge, 10mm tip Venom Cannula; and (4) 100mm, 18-gauge, 10mm tip standard RF cannula. Elec- trodes were inserted into the four cannulae and thermal lesions were created on all four channels with temperature control at 80°C for 90 seconds using the Stryker MultiGen Radiofrequency Genera- tor (Stryker Instruments, Kalamazoo, Michigan). The real-time pow- er output data was recorded from all four channels. Sponsored by:

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