Conventional vs Bipolar SIJ RFA for Treatment of Sacroiliac Joint Pain

Low back pain affects the majority of individuals at some time in their lives. The estimated point prevalence of low back pain in 2015 was 7.3%, indicating that 540 million may be affected at any given time (1). The etiology of low back pain may be multifactorial but commonly is often attributed to nociception arising sacroiliac joint complex (SIJC) in as many as 15-30% of patients (2). The SIJC is a diathrodial, synovial joint that receives both anterior innervation from the lumbosacral plexus as well as posterior sensory innervation via the posterior sacral network (PSN) (3). The PSN is comprised by the lateral branches S1-S3 posterior rami, with variable contributions from S4 lateral branch, L4 medial branch, and L5 dorsal ramus (3-6). These have been targeted for neurotomy most commonly with image-guided percutaneous radiofrequency ablation (RFA) (7), but also with percutaneous cryoneurolysis (8), chemical neurolysis (9), endoscopic-guided RFA (10), and MRI high frequency ultrasound treatment (MRI-HIFU) (11). Prior systematic review has suggested that 32-89% of patients may achieve at least 50% pain relief for six months, while 11-44% of patients achieved 100% pain relief for the same period (12). Although elements of patient selection likely affect this estimate (13), studies have used a variety of different RFA techniques to target the PSN which also may impact success rates. Few studies have directly compared these techniques, but cadaveric work has suggested that targeting the PSN with bipolar strip lesions results in substantially higher rates of neural capture compared to periforaminal RFA performed with conventional monopolar electrodes (6). Further, the rate of complete neural capture with a periforaminal conventional monopolar RFA may be as low as 12.5%, which is perhaps one reason why some clinical studies have shown increased probability of success in groups treated with technologies known to create larger lesions (13,14). Similar effectiveness has been observed for periforaminal techniques with both conventional monopolar compared to larger cooled monopolar lesions (15), as well as between large continuous-lesion multi-electrode lesioning compared to periforaminal conventional monopolar technique (16). However, no study has directly compared a bipolar strip lesion using a "palisade" technique (N-SIJRFA) to a conventional monopolar periforaminal method, the latter of which is used commonly in many practice settings. The primary purpose of the current study is to evaluate the effectiveness of RFA of the PSN using a bipolar "palisade" technique to create a continuous strip lesion compared to conventional monopolar periforaminal technique in the treatment of patients with sacroiliac joint complex pain. Given the findings of recent cadaveric studies, the results of the proposed work may substantially impact the current treatment paradigm for PSN neurotomy.