Novel use of ultrasound-guided high-intensity focused ultrasound (HIFU) may enable the neuroablation of the sacroiliac joint in a swine model: a feasibility study

Sacroiliac joint (SIJ) dysfunction accounts for the etiology of pain in 15%-30% of low back pain cases. Some patients with conservative treatment-refractory SIJ dysfunction undergo radiofrequency (RF) ablation of the SIJ for prolonged pain relief. This procedure involves placing up to 12 RF probes in what is an invasive, resource-intensive, and time-consuming process. High-intensity focused ultrasound is an alternative neuroablative technique that is non-invasive and potentially less cumbersome. MRI-guided high-intensity focused ultrasound (MRgHIFU) had previously been successfully applied to SIJ ablation in a swine model, and more recently had been trialed in humans. However, ultrasound-guided high-intensity focused ultrasound (USgHIFU) of the SIJ may be a more practical and rapid alternative to MRIgHIFU. This was a prospective technology efficacy and safety study in a swine model. Three Yorkshire pigs underwent bilateral SIJ ablation using a proprietary USgHIFU prototype. Post procedure, treatment efficacy was assessed using clinical evaluation of pain and changes in ambulation, gross inspection of lumbosacral necropsy and pathology sections, and histology. Post anesthetic monitoring for 72 hours showed no signs of gait abnormalities or perceived pain in the swine models. Of the primary sacral spine targets, histological specimen review suggested successful lesioning of 37/54 sites (68.5%), specifically in the targeted areas that were visualized under ultrasound. Of the successful lesion zones, 22/37 (59.5%) included nerve lesions, 34/37 (91.9%) included muscle lesions, 34/37 (91.9%) included periosteum lesions, and 20/21 (95.2%) included bony lesions. The preliminary study thus demonstrates that USgHIFU can create targeted contiguous strip lesions along the SIJ and lead to thermal necrosis of the posterior sacral network without causing additional neurological damage or damage to adjacent muscle tissue or bone outside of target areas.