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.