Medial Branch Block Procedure for Facetogenic Lumbar Pain
The medial branch block procedure for facetogenic lumbar pain should target the groove at the cephalad margin of the transverse process adjacent to the superior articular process, with fluoroscopic guidance considered mandatory for optimal accuracy and safety. 1
Patient Selection and Diagnostic Criteria
- Diagnostic facet blocks should be performed using the double-injection technique with an improvement threshold of 80% or greater to establish the diagnosis of lumbar facet-mediated pain 2, 3
- Advanced imaging (MRI or CT) is essential before proceeding with facet procedures to rule out other causes of spinal pain such as herniated discs, spinal stenosis, fractures, or tumors 4
- Patients should have symptoms suggestive of facet joint syndrome, positive provocative testing on physical examination, and pain persisting despite at least 6 weeks of conservative treatment 3, 5
Procedural Technique
Fluoroscopy-Guided Approach (Standard)
- Position the patient prone on the procedure table with a pillow under the abdomen to reduce lumbar lordosis 1
- Identify the target lumbar level using fluoroscopy in the anteroposterior (AP) view 1
- The target point is the groove at the cephalad margin of the transverse process adjacent to the superior articular process 1
- After sterile preparation and local anesthesia:
Single Needle Technique Variation
- A single needle approach can be used for multiple medial branch blocks using only the AP fluoroscopic view 6
- Initially direct the needle toward the medial branch at the affected facet joint level 6
- After anesthetizing this nerve, withdraw the needle to the subcutaneous tissue and reposition to block the medial branch above, and then below 6
- This technique may reduce patient discomfort, procedure time, radiation exposure, and volume of local anesthetic used 6
Ultrasound-Guided Approach (Alternative)
- Ultrasound guidance has shown a 95% success rate when compared with fluoroscopic confirmation 1
- Use a paravertebral cross-axis view and long-axis view with high-resolution ultrasound (2-6 MHz) 8
- Identify the transverse process and superior articular process junction as the target point 8
- The skin-target distances increase from L3 to L5 (approximately 44-50 mm) 8
- While promising, this technique requires further studies regarding detection of intravascular spread 1
Post-Procedure Assessment
- Document pain reduction using a validated scale (e.g., Visual Analog Scale) 1, 7
- A positive diagnostic block is considered when there is at least 80% pain relief 2, 3
- For therapeutic purposes, the average duration of pain relief with each procedure is approximately 12-15 weeks 7
Important Considerations and Pitfalls
- Performing facet procedures without proper imaging can lead to misdiagnosis of the pain generator or treatment of the wrong spinal level 4
- Intravascular needle placement is a potential complication that must be ruled out with contrast injection 1
- Only one invasive modality or procedure should be performed at a time for treating back pain 5
- Intra-articular facet injections are not recommended for chronic low back pain from degenerative lumbar disease (Level II evidence against) 2, 3
- For therapeutic purposes, facet medial nerve blocks have moderate evidence supporting their use for short-term pain relief 2, 9
Follow-up Management
- If diagnostic blocks are positive, consider radiofrequency ablation for longer-term pain relief 2, 9
- The outcome of radiofrequency treatment is not significantly different between patients reporting over 80% pain relief after diagnostic block versus those reporting 50-79% pain relief 9
- For therapeutic medial branch blocks, the average number of treatments needed per year is approximately 3-4 7