Ultrasound-guided lumbar facet nerve block: a sonoanatomic study of a new methodologic approach

BACKGROUND: Lumbar facet nerve (medial branch) block for pain relief in facet syndrome is currently performed under fluoroscopic or computed tomography scan guidance. In this three-part study, the authors developed a new ultrasound-guided methodology, described the necessary landmarks and views, assessed ultrasound-derived distances, and tested the clinical feasibility. METHODS: (1) A paravertebral cross-axis view and long-axis view were defined under high-resolution ultrasound (15 MHz). Three needles were guided to the target point at L3-L5 in a fresh, nonembalmed cadaver under ultrasound (2-6 MHz) and were subsequently traced by means of dissection. (2) The lumbar regions of 20 volunteers (9 women, 11 men; median age, 36 yr [23-67 yr]; median body mass index, 23 kg/m2 [19-36 kg/m2]) were studied with ultrasound (3.5 MHz) to assess visibility of landmarks and relevant distances at L3-L5 in a total of 240 views. (3) Twenty-eight ultrasound-guided blocks were performed in five patients (two women, three men; median age, 51 yr [31-68 yr]) and controlled under fluoroscopy. RESULTS: In the cadaver, needle positions were correct as revealed by dissection at all three levels. In the volunteers, ultrasound landmarks were delineated as good in 19 and of sufficient quality in one (body mass index, 36 kg/m2). Skin-target distances increased from L3 to L5, reaching statistical significance (*, **P < 0.05) between these levels on both sides: L3r, 45+/-6 mm*; L4r, 48+/-7 mm; L5r, 50+/-6 mm*; L3l, 44+/-5 mm**; L4l, 47+/-6 mm; L5l, 50+/-6 mm**. In patients, 25 of 28 ultrasound-guided needles were placed accurately, with the remaining three closer than 5 mm to the radiologically defined target point. CONCLUSION: Ultrasound guidance seems to be a promising new technique with clinical relevance and the potential to increase practicability while avoiding radiation in lumbar facet nerve block.