Low back pain constitutes the majority of musculoskeletal problems seen in chronic pain settings. The lifetime incidence of back pain has been reported to be between 54%-80% [1-3]. Lumbar facet joint pain is a syndrome in which the zygapophysial joints cause back pain.  It may account for as much as 14%-45% of those patients experiencing chronic LBP [4-6].
Facet Joint Osteoarthritis Treatment Options
Facet joint interventions, including intraarticular injections, medial branch nerve blocks, and neurotomy (radiofrequency and cryoneurolysis) are used to manage chronic facet-mediated spinal pain. Radiofrequency ablation to induce thermal necrosis of the facet neural fibers has been reported to provide significant pain reduction in patients for 6-12 months [7, 8]. However. complications from these techniques may occur. These include discomfort around the injection site, numbness of the skin, neuritis, pain from muscle spasm at injection site, permanent nerve pain and reactions to administered medications .
MR guided Focused Ultrasound provides a non-invasive method of facet denervation that provides pain relief without invasive procedural complications. 
ExAblate- MR guided Focused Ultrasound for Facet Joint Osteoarthritis
ExAblate uses MR guided Focused Ultrasound as a non-invasive thermal ablation technique to relieve back pain caused by facet joint osteoarthritis with minimum effect of the surrounding tissues. The palliative effect of MRgFUS is based on destruction of periosteal denervation by controlled heating.
The focused ultrasound energy is focused onto a small area of the painful joint, thermal energy is deposited resulting in protein denaturation at temperatures above 55 C for one second. Heating the peri-articular tissue beyond this threshold for a few seconds, results in local tissue necrosis, which causes denervation of the network of nerves around the facet joint. The FUS beam is then focused onto another facet and this new area is treated. The process is repeated until all the nerves causing the pain are destroyed. In clinical studies on average 5 [4-10] facet joints have been treated during one treatment session.
a Axial: Showing pretreatment beam angulation to avoid spinous process and spinal canal.
b Sagittal: Showing pre-treatment beam angulation to avoid the spinous process and spinal canal
Benefits of Focused Ultrasound for Facet Joint Osteoarthritis
The benefits of ExAblate for facet joint denervation include:
- Non-invasive therapy for facet joint pain
- No needles involved
- No exposure to ionizing radiation (as in fluoroscopy)
- All involved facet joints can be treated in one session
- Real-time image control and thermal feedback minimize complications
- An effective and safe thermal ablation technique for facet joint pain
In addition, MRI can help increase the diagnostic certainty of facet joint disease
Weeks, Platt and Gedroyc report on the safety and efficacy of eighteen patients treated with ExAblate with MRgFUS for facet joint lower back pain. 
The mean age of patients was 48.2 years and mean BMI was 28.2. The mean number of joints treated was five (4-10). Mean pain score, measured by 0-10 numerical rating scale (NRS), pre-treatment was 6.42 (average) and 7.96 (worst). A reduction in the NRS average pain score of 3.87 (60.2%) and NRS worst pain score of 4.08 (51.5%) was found at 6/12 months. This was associated with a 45.88% improvement in the low back pain dedicated Oswestry Disability Questionnaire score and a 61.90% reduction in the brief pain inventory (BPI) interference in life score questioner.
The findings confirmed the inherent safety of MRgFUS. There were no recorded treatment complications or related thermal side effects.
The safety and efficacy demonstrated that MRgFUS resulted in improvements in both pain scores and functional disability measures at each follow-up time point from 1 week post treatment to 6 months after treatment. These results are similar to those reported by treatment of RF denervation.
Clinical Case: 35 Year Old Female, L4-L5, L5-S1 (Bilateral) Treated
Patient experienced significant pain relief following treatment with no adverse events
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