MRI-guided focused ultrasound ablation of painful lumbar facet joints: a retrospective assessment of safety and tolerability in human subjects.

OBJECTIVE: To evaluate the safety and tolerability of MRI-guided focused ultrasound (MRgFUS) for the treatment of facet joint mediated pain in human subjects who failed conventional treatment. Secondarily, to evaluate effectiveness of the procedure.

SUBJECTS AND METHODS: Consecutive patients who underwent MRgFUS at our institution were retrospectively identified. Chart review was performed to obtain relevant clinical and technical data. All patients had chronic low back pain and positive comparative medial branch blocks.

RESULTS: Twenty-six MRgFUS treatments in 20 patients were included. Mean sonication energy was 1436.6 Joules. The procedure was technically successful in all patients. 29.6% of patients experienced short-term worsening of low back pain immediately following the procedure, all by 1-4 points on a 0-10 scale. One patient (3.8%) reported temporary worsening of pre-existing radicular symptoms after the procedure. Of 21 patients with clinical follow up of at least 3 months available, 12 (57.1%) had >3 months pain relief, 2 (10%) had <3 months benefit, 6 (30%) reported no benefit, and 1 (5%) patient was lost to follow up. In patients who reported at least some benefit to prior conventional RF ablation, 8/10 (80%) benefitted from the MRgFUS procedure.

CONCLUSION: The current study demonstrates that MRI-guided focused ultrasound ablation of the lumbar facet joints is a safe and tolerable procedure in human subjects, and may provide another option for patients who fail RFA. Over half of all patients received significant durable pain relief, which jumped to 80% for patients who had at least some benefit from prior RF ablations.