Safety of Lumbar Spine Radiofrequency Procedures in the Presence of Posterior Pedicle Screws: A Prospective Trial

This study was a prospective clinical trial, examining outcomes related to temperature increases in pedicle screws. It was not possible to blind the investigators or the patient. Outcomes related temperature differences were collected at each pedicle screw adjacent to a zygapophyseal joint being treated.

A conventional 18-gauge, 1-cm curved active tip radiofrequency cannula was placed under fluoroscopic guidance to the area to be treated (the junction of the transverse process and the superior articulating process of the facet joint). This position placed the tip of the radiofrequency cannula immediately adjacent to, but not in direct contact with, the pedicle screws. The radiofrequency cannula was connected to a radiofrequency generator, and the conventional settings for clinical medial branch neurotomy was used, heating the tissue to 80°C for 90 seconds. The procedure described up to this point is the normal procedure and protocol for RFN performed at the Mayo Clinic.

The experimental portion of the procedure is as follows: A separate 22 gauge radiofrequency cannula was intentionally placed in direct contact with the dorsal surface of the pedicle screws and was connected to a radiofrequency generator solely for the purpose of measuring temperature, as the RF cannula are dual purpose probes capable of both conducting energy for the radiofrequency lesion and monitoring tissue temperature. In other words, this small gauge needle was placed for the sole purpose of acting as a thermistor probe/temperature monitor. This process was repeated for each level necessary for treatment.