Safety of Lumbar Spine Radiofrequency Procedures in Patients Who Have Posterior Spinal Hardware
Tim J. Lamer MD, Jolene Smith DO, Halena M. Gazelka MD, Bryan C. Hoelzer MD, William D. Mauck MD, Wenchun Qu, MD, MS, PhD
Division of Pain Medicine, Mayo Clinic, Rochester MN
Patients with previous lumbar instrumented fusion frequently develop adjacent segment degenerative changes in the facet joints and may be considered candidates for radiofrequency facet neurotomy (RFN). A recent cadaver study demonstrated the potential for hardware and adjacent tissue heating during RFN in the presence of adjacent pedicle screws1.
Accordingly, this study was performed to assess the possibility of heat transfer to pedicle screws in human subjects undergoing RFN.
The study was conducted after Mayo Clinic IRB approval. Patients, who had lumbar facet pain adjacent to a previous instrumented fusion, as demonstrated by greater than 75% pain relief from differential MBBs, underwent lumbar RFN using conventionally accepted RF energy settings. At the level adjacent to pedicle screws, the RF cannula was placed as close to the conventional MBB target as possible but without direct contact with the screw (figures). Continuous temperature of the pedicle screw was monitored throughout the procedure via a thermistor probe placed on the dorsal surface of the screw. For safety purposes we chose to abort the procedure if the temperature reached 42 degrees C.
6 patients underwent a total of 10 RF cannula placements adjacent to pedicle screws for a total of 10 attempted RFN lesions. The temperature of the fusion hardware increased in 6 of the 10 RF lesion procedures. During 2 of the procedures, the temperature rose rapidly to 42°C, at which time the procedure was ceased at that level (table).
This study demonstrated that radiofrequency lesioning to treat symptomatic facet joint pain in patients who have adjacent posterior lumbar fusion hardware may result in heat energy being transferred to the adjacent hardware. This may increase the risk of injury to the patient. Monitoring for a temperature increase is easily accomplished by inserting a temperature probe onto the surface of the hardware.
Gazelka HM, Welch TL, Nassr A, Lamer TJ. Pain Med. 2015 May;16(5):877-80.
Disclosure and Conflict of Interest: This study was supported by a grant from
the Department of Anesthesiology Small Grants Program, Mayo Clinic, Rochester,
Minnesota. The authors have no conflicts of interest to disclose.