Radiofrequency ablation of the basivertebral nerve as potential treatment of back pain: pathologic assessment in an ovine model (Invited Paper)

Pathological involvement of the basivertebral nerve (BVN), an intraosseous vertebral nerve, may play a significant role in some forms of back pain. This study was designed to assess the feasibility and effects of thermal ablation of the lumbar basivertebral nerve in mature sheep. Sixteen adult female sheep weighing 65-80 kg were anesthetized and positioned for ventral recumbent surgery. Under fluoroscopic guidance, two bilarterally oposed 5mm active length rediofrequency (RF) electrodes (1.65mm diameter were perfutaneously placed in select lumbar vertebrae at a relative angle of 70 degrees with a 5 mm tip separation. The elctrodes were advanced to the region of the vertebral bodies which contained the BVN. A thermal dose of 95° C/720 seconds was administered. Animals were survived for 2, 14, 90, or 180 days post-treatment. Clinical, radiologic and pathologic investigations were performed to determine the effect of the heat on the BVN and associated tissues. Thermal damage to the basivertebral neurovascular bundle was characterized by early hemorrhage and necrosis, followed by inflammation and fibrosis. Although there wasa significant revascularization of the treated bone marow regions, there was no evidence of basivertebral nerve survival or regeneration regeneration. In addition to ablation of teh basivertebral nerovascular bundle, the areas receiving the greatest treatment demonstrated initial mild local osteolysis and demineralization of the vertebral body bone and regional depopulation of the vertebral bone marrow cellular elements. Significant bone remodeling in the affected areas had begun by 14 days post-treatment. Bone remodeling was characterized by conventional osteoblast proliferation, osteoid deposition, and mineralization. This study demonstrated the ability to accurately, reproducibly, and safely ablate the basivertebral nerve and neurovascular bundle in mature sheep using a fluoroscopically guided percutaneously delivered radiofrequency technique.