Anatomical study on radiofrequency ablation for the treatment of lumbar facet joint syndrome

Study Design: Anatomical study. Background: While radiofrequency ablation (RFA) is a well-established and effective treatment for lumbar facet joint syndrome (FJS), some studies have reported that pain relief in certain patients is limited, with symptoms potentially recurring within 1-2 years following medial branch RFA. A deeper understanding of the course and distribution of the medial branches of the dorsal rami from their origin to the fibro-osseous canal entrance could enhance the success rate of RFA for denervation. This study investigated the anatomical characteristics of the medial branches of the dorsal rami of L1-L4 and explored their potential clinical significance. Methods: An anatomical examination was conducted on ten human specimens to document the characteristics of the medial branches of the dorsal rami of L1-L4. Results: The angles between the medial branches of the dorsal rami and the MAL at the fibro-osseous canal entrance were as follows: 65±3°, 66±3°, 68±3° and 67±4°, respectively. The distances from the caudal aspect of the mamillary process to the medial branches at the fibro-osseous canal entrance were measured as 4.66 ± 1.02 mm, 4.80 ± 1.08 mm, 5.15 ± 1.23 mm, and 5.07 ± 0.99 mm, respectively. Conclusion: To optimize RF denervation, the electrode should form an angle of approximately 60-70° with the line connecting the mamillary process to the accessory process. The distal tip of the RF electrode should be positioned 3-6 mm below the caudal mamillary process at the fibro-osseous canal entrance, which may improve parallel tip alignment and selectivity for the targeted nerves.