Sent to attorneys August 20, 2026.
A short note on the nomenclature attorneys see in cervical and lumbar spine records. It matters because the numbering conventions differ, and a report that reads clean at first glance can name a different anatomy than the reader assumes.
Every facet joint[1] is named for the two vertebrae that form it — the C5-6 facet is the joint between C5 and C6, the L4-5 facet the joint between L4 and L5. Every facet joint has a DUAL nerve supply from two medial branches[2]: the one from its own level, and the one from the level above. That is why a diagnostic block always targets two nerves for each joint.
Cervical numbering aligns cleanly with the labeling. To block the C5-6 facet, the C5 and C6 medial branches are the targets, and the injection report will name them by those numbers. The one well-known cervical exception is the C2-3 facet, which is supplied by the third occipital nerve[3], a specialized superficial branch of the C3 dorsal ramus. A C2-3 facet workup for headache of cervical origin therefore targets the third occipital nerve rather than a generic “C2 medial branch,” and reports may name either the TON or the C2-3 facet by name.
Lumbar numbering does not align as cleanly, particularly at the last level. From L1 through L4, each dorsal ramus divides into a medial branch and a lateral branch in a predictable pattern, and each facet joint follows the same “own level plus one above” rule — an L3-4 facet block anesthetizes the L2 and L3 medial branches. The L5-S1 facet is anatomically different, and that difference is the reason a separate note follows this one; the short version is that a report reading “L5-S1 medial branch block” does not describe two ordinary medial branches, and the label alone should not be read literally without looking at the actual needle positions and the fluoroscopic images.
Medical terms
[1] Facet joint — the paired small joints at the back of each spinal level, one on each side. They allow adjacent vertebrae to glide against each other during motion and are a common source of neck and low-back pain.
[2] Medial branch — a small nerve twig that comes off the dorsal ramus (the back-turning branch) of a spinal nerve, immediately after the nerve exits the spine. Medial branches carry the pain signals from the facet joints they supply; blocking or ablating them is how facet-generated pain is diagnosed and treated.
[3] Third occipital nerve (TON) — a specialized superficial branch of the C3 dorsal ramus that supplies the C2-3 facet joint and the skin over the back of the head. Its involvement is what makes C2-3 the anatomic target for post-injury headache of cervical origin.
I hope you found this interesting.
Questions or comments about today’s educational update, or a topic you would like us to address in a future edition? Contact us through our website: OrthOpinions
F. Allen Johnston, MD
Louisiana Orthopedic Institute
Baton Rouge
(225) 751-6666 Office
(225) 270-0000 Cell
