Moossy Lumbar Rhizotomy

Last modified by XWikiGuest on 2023/12/26 18:14

Preop

You will need lead and a C-arm for this case. You will pretty much only take AP shots. No C armor is necessary.

If the patient has had a prior rhizotomy, know what levels were done and at what setting. For patients who have had multiple previous rhizotomies, 90 seconds at 90 degrees C is standard.

Anatomy

The goal of the procedure is to ablate the medial branch nerve.

In the fluoro shot below, the black circle outlines the approximate location of the L4/5 facet joint.

Innervation to the joint comes from two locations:

The L3 medial branch, which runs over the L4 transverse process before dividing into a superior articular branch which innervates the L3/4 facet and an inferior articular branch which innervates the L4/5 facet.
The L4 medial branch, which runs over the L5 transverse process before dividing into a superior articular branch which innervates the L4/5 facet and an inferior articular branch which innervates the L5/S1 facet.

So, to denervate the L4/5 facet, radiofrequency ablation should be delivered to the L3 and L4 medial branch nerves. The targets are the lateral borders of the L4 and L5 pedicles on an AP projection.

In the middle oblique fluoro shot above, "mb" connotes medial branch, "a" connotes articular branch, and "dr" dorsal ramus.

Positioning

Regular OR bed. Set up bed with pillows and padding for the chest and knees. Foam donut for the head and face.

Patient lies face-down on the OR table. They position themselves.

Anesthesia is MAC only, no ET tube.

Prep

At the VA, Moossy uses chlorhexidine preps only

Draping

Four blue towels in a square followed by ioban. Moossy usually only applies the down drape in a universal pack and does not apply the sides and top.

Procedure

Use lidocaine to raise a weal 2-3 cm lateral to midline at each level that will be treated.

Place an instrument on the patient's right to define sided-ness.

Place a needle down to bone at the topmost level on one side and at the next level down on the contralateral side. It is done this way so you easily know which side is which because the right and left sides are at different levels. Take a shot.

Position the needles such that the tip is resting on bone and at the lateral border of the pedicle. Each level is treated at the upper-lateral and lower-lateral corner of the pedicle.

Two lesions are created at each level to accommodate possible variations in the exact location of the nerve.

Deliver the radiofrequency ablation dose - usually 90 degrees C for 90 seconds.

Replace the stylet and reposition the needle, then treat the lower (or upper if you started with lower) corner.

Once both the upper and lower corners have been treated, administer ~3 ccs of bupivicaine down the needle before removing. Give bupivicaine only after you have treated both corners of since instillation of fluid can displace structures and alter target anatomy.

Treat the remaining levels. The image below shows needle placement at bilateral L3 pedicle.