Position and anatomical landmarks
The patient lies in a prone position on the operating table. In contrast to intra-articular test blocks, there is controversy about RF treatment of the medial branches of the dorsal branch at the thoracic level.
The following technique is recommended. The C-arm is positioned in the axial plane and a steel ruler identifies the proper level. A perfect AP fluoroscopic view shows the end plates of the vertebrae to be neatly projected over one another. The C-arm is rotated obliquely and the final position of the tip of the needle is the junction between the superior articular process of the facet joint and the transverse process (Figure 1).
Figure 1. Thoracic facet joint denervation: needles in AP view.
The site of insertion of the needle is marked on the skin and an RF needle is inserted parallel to the C-arm until contact is made with the bone at the junction between the superior articular process and the transverse process. The needle is then positioned slightly more cranially and laterally, and is monitored from a lateral position (Figure 2).
Figure 2. Thoracic facet joint denervation: needles in lateral view.
The tip of the needle should be posterior to the line that connects the anterior aspects of the intervertebral foramen. Thereafter, neurostimulation initially takes place with 50 Hz, and then with 2 Hz. The 2 Hz stimulation causes the paravertebral muscles to contract at intensities below 0.5 to 0.7 V. After local anesthetic has been injected, a 60-second 20 V RF treatment at 80°C is carried out. We usually perform this RF treatment at three adjacent levels, due to the multi-segmental innervations of the facet joints.
- The most frequent complication is after-pain, which can last a few days.
- The most serious complication is pneumothorax, which will necessitate drainage.