Anatomical study of the medial branches of the lumbar dorsal rami: implications for image-guided intervention

Abstract

IntroductionFluoroscopic-guided radiofrequency ablation of the lumbar medial branches is commonly performed to manage chronic low back pain originating from the facet joints. A detailed understanding of the course of medial branches in relation to bony and soft tissue landmarks is paramount to optimizing lumbar denervation procedures, particularly parallel placement of the radiofrequency electrode. The objectives of this study were to investigate the relationship of medial branches to anatomical landmarks and discuss the implications for lumbar denervation.MethodsTen cadaveric specimens were meticulously dissected. The origin, course, and relationship of lumbar medial branches to bony and soft tissue landmarks were documented.ResultsThe medial branches followed the lateral neck of superior articular process deep to the intertransversarii mediales muscle at each lumbar vertebral level. In all specimens, the medial branches coursed laterally on the anterior half of the neck and transitioned from parasagittal-to-medial on the posterior half to reach the mamillo-accessory notch. The mamillo-accessory ligament was found to not occlude the nerve on the posterior quarter of the lateral neck but rather at the mamillo-accessory notch located at the posterior margin of the superior articular process.DiscussionA detailed understanding of the relationship of medial branches to anatomical landmarks is essential to optimizing needle placement for lumbar denervation procedures. The current study suggests that a parasagittal placement, with increased cranial-to-caudal angulation of the electrode, may improve parallel tip alignment with the targeted medial branch and represent a potential alternative to the traditional technique.

Letter to the editor regarding ‘Anatomical study of the medial branches of the lumbar dorsal rami: implications for image-guided intervention’

“…Contact with conductive muscle tissue shunts electrical energy and insulates nearby tissues from thermal energy, diminishing effectiveness of LMBRFC 6. This further emphasizes the agreement among the authors, Lau et al , and SIS on the importance of maximal contact of active electrode on the exposed MB, in close proximity to the periosteum of the lateral SAP 1 3 5…”

“…We wholeheartedly support the author’s emphasis on the location of the mamillary and accessory processes as the anchor for understanding the location of the MBs and find the proposed fluoroscopic landmarks for estimation of the MB location in figure 13 invaluable 1…”

“…The anatomical dissection of the lumbar dorsal rami and their branches performed by Tran et al 1 was meticulous, well written and informative. We offer our thoughts and comments in the spirit of collaboration to advance the practice of lumbar medial branch (MB) radiofrequency coagulation (LMBRFC).…”

“…Regarding the authors’ final point, the risk of inadvertent dorsal ramus or intermediate branch lesioning using the ‘traditional’ approach targeting the mid-SAP remains unlikely 3. The illustrations do not reflect the full three dimensions of the relevant anatomy: the dorsal ramus is generally found several millimeters superior to the ventral transverse process and in the neural foramen 1 4. There may be anatomical variations where lesion placement using customary landmarks could diminish the effectiveness of the procedure, and pelvic structures may restrict access to the lateral SAP; for these cases, we welcome the authors’ recommendations for dorsal SAP lesions close to the MAL.…”

“…Unfortunately, the authors seem to have misrepresented the declination of cannula recommended by anatomically based technical descriptions of LMBRFC 1 3. The descriptions and images from the primary counterexample offered in the text3 recommend an identical declination to the authors’ preferred approach, which is reflected in the Spine Intervention Society (SIS) practice guidelines 5.…”