Extravertebral temperature exposure during spinal radiofrequency ablation: an experimental surrogate assessment of neural injury risk

BACKGROUND: Radiofrequency ablation (RFA) has become an important minimally invasive option for the treatment of painful spinal tumors and benign bone lesions. While its effectiveness within the vertebral body is well established, there is ongoing concern about unintended heat exposure of nearby neural structures. Experimental data describing how heat propagates beyond the vertebra during spinal RFA are still limited. This experimental in vitro study aims to assess the extravertebral temperature exposure during spinal radiofrequency ablation as a surrogate parameter for potential neural injury risk under controlled conditions. METHODS: This experimental in vitro study was performed on four fresh-frozen human lumbar spines. Radiofrequency ablation was carried out using a commercially available system and standard clinical protocols. Two anatomical configurations were examined: ablation within the vertebral body and ablation within the pedicle. Temperatures were measured at predefined locations outside the vertebra, including the spinal canal and cortical boundaries, using multiple thermocouples. To aid interpretation of radiofrequency-related measurement artifacts, an additional control setup using an electrothermal heating system without radiofrequency energy was included. Temperature data were evaluated descriptively. RESULTS: In the control experiments, temperature profiles were consistent across all measurement sites, and no values exceeded 42 °C. During radiofrequency ablation, temperature recordings showed pronounced fluctuations related to electromagnetic interference. In the pedicle configuration, temperatures rose gradually during energy delivery and decreased after the procedure, with maximum values reaching up to 44 °C. Although temperatures above 42 °C occurred intermittently, no sustained exposure above 45 °C was observed at any extravertebral location. CONCLUSIONS: Under controlled in vitro conditions and with intact cortical bone, spinal radiofrequency ablation led to limited heat propagation beyond the vertebral body and pedicle. Temperature levels commonly associated with irreversible neural injury were not reached or were exceeded only briefly. These findings suggest a low risk of clinically relevant thermal injury to adjacent neural structures when spinal RFA is performed with appropriate probe placement and preserved osseous integrity. Caution is warranted when applying these results to clinical situations involving cortical destruction or altered vertebral anatomy.