Comparison of Methods of Lumbar Sympathetic Ganglion Block: Distance vs Angle

Lumbar sympathetic ganglion block is used for several neuropathic pain syndromes. The best method of lumbar sympathetic ganglion block is not established. The investigators would compare two methods of lumbar sympathetic ganglion block. One is modified Reid method which's entry point is 7~7.5cm from midline of spinous process of lumbar spine. The other is angular method which's entry angle is 30 degree from anterior-posterior view of C-arm. Comparison modified Reid method with angular method would be helpful for finding best method of lumbar sympathetic ganglion block.