Ablation of the sacroiliac joint using MR-guided high intensity focused ultrasound: a preliminary experiment in a swine model

BACKGROUND Dysfunction of the Sacroiliac Joint (SIJ) is one of the key sources of low back pain. For prolonged pain relief, some patients undergo fluoroscopic guided radio-frequency (RF) ablation of SIJ, during which a number of RF probes are inserted to create thermal lesions that disrupt the posterior sacral nerve supply. This procedure is minimally invasive, laborious, time-consuming and costly. To study if High Intensity Focused Ultrasound (HIFU) ablation is a feasible alternative approach to SIJ pain treatment, we performed experiments using HIFU to ablate SIJ in the swine model. METHODS Three female Yorkshire swine (36, 35.2 and 34 kg) underwent bilateral Magnetic Resonance guided HIFU (MRgHIFU) ablation of the SIJs. Treatment assessment was performed using contrast-enhanced imaging, histopathology and evaluation of pain and changes in ambulation and gait. RESULTS Contiguous lesions along the right and left SIJs were achieved in all animals. In one out of three animals, excessive heating of the muscle and skin tissue in the near-field resulted in unwanted muscle necrosis. No changes in animal behavior, ambulation or gait were detected. CONCLUSIONS The initial experiments with MRgHIFU ablation of SIJs in sub-acute swine model show promise for this ablation modality as a non invasive and more precise alternative to the currently used fluoroscopically - guided RF ablations and injections.