Medial Branch Blocks, Facet, Or Zygapophyseal Joint Injections

by  Find-A-Code™
Jan 1st, 2019 - Reviewed/Updated Apr 30th

Medial branch and lateral branch blocks are spinal pain procedures which have been a source of confusion for many coders. The following should clarify the what, why, and how of these beneficial injections. Medial branch blocks (MBBs) are the same as facet joint injections in that the surgeon is injecting the medial branches of the nerves (cervical, thoracic, or lumbar) that innervate the paravertebral facet (zygapophyseal) joints.

Medial branch blocks (MBBs) include the following codes by spinal region:

64490-64492 (cervical/thoracic)
64493-64495 (lumbar/sacral)

Each facet joint is innervated by two medial branch nerves: the nerve that hangs down from the joint above it and the nerve that pertains to it. The following 2 examples demonstrate coding these services.

Joint Injection Example 1

“Injection of L3 and L4 will completely block L4.” How the procedure is documented in the operative report is important. Some providers describe the blocked nerves by listing the vertebral segment levels with a hyphen (e.g., L3–4 or L3-L4). Others list each nerve individually, separated by commas (e.g., L3, L4). Regardless of the documentation style, you can determine the number of vertebral segments treated by counting the number of nerves blocked and subtracting one. Alternatively, identify each fully blocked joint and count them individually.

Tip: Two nerves must be blocked in order for a single facet joint to be blocked and qualify for one unit of service.

Joint Injection Example 2

If the report reads facet injection of L3-4, L4-5, this means the L3, L4, and L5 nerves were injected to block sensation in the L4 and L5 facet joints. L4 was blocked by injecting L3 and L4. L5 was blocked by injecting L4 and L5. This would be reported like this:

   64493 – Injection, lumbar or sacral facet joint, first level
+64494 – Injection, lumbar or sacral facet joint, second level (add-on)

If T3-4, T4-5, T5-6 were injected, then a total of four nerves were injected (T3, T4, T5, T6) or three joints (T4, T5, and T6).

More about Joint Injection Coding

One more caveat is that there is a CPT guideline that states when T12, L1 nerves are injected, you must code 64490. This does not follow the normal rules, it is an exception and should be adhered to. For example: If T11-T12, T12-L1 are injected, the coding would go as follows:

According to the CPT guidelines “For paravertebral facet injection of the T12-L1 joint, or nerves innervating that joint, use 64490”. Therefore, T12-L1 is reported with 64490, and T11-T12 would be reported with 64491. If there were other joints or nerves injected, you would code the remaining levels accordingly.

Example: Injection of L3-4, L4-5, L5-S1 (also written as nerve injections including L3, L4, L5, S1) would entirely block the L4, L5, and S1 joints. This would be coded as 64493 (L4) and 64494 (L5), and new code 64451 (S1), because the S1 joint nerves have their own code as of 2020.

Tip: Medial branch blocks cannot be billed unless they are performed under image guidance and localization. If imaging is not used, report 20552 or 20553. If ultrasound guidance is used, report a code from 0213T-0218T.

Note: Payers primarily distinguish facet joint injections vs medial branch blocks (MBBs) based on documentation intent, anatomical target, procedural technique, and medical necessity logic, not just CPT code selection. Documentation needs to be clear to support the code selected (e.g., is the injection “in the facet joint space” or “around the nerve”).