Dorsal Sacroiliac Joint RF Denervation "Continuum Procedure"
BACKGROUND:
Increasing awareness of sacroiliac joint pain has led to the need for a simple, economical, and reliable technique for dorsal SIJ RF denervation. The highly variable dorsal innervation of the SIJ requires a robust technique to reliably lesion the lateral branches of S1, S2, and S3, as well as the dorsal ramus of L5 when present. An ideal lesion extends from the base of the S1 SAP and extends to a point lateral to the S3 PSFA. The lesion should be positioned <10 mm lateral to the S1-S3 PFSA and is approximately 10 mm wide and 10 mm deep to encompass variable anatomy and create a wide enough interruption in the lateral branch to support durable clinical response.
The Nimbus MEE was tested ex-vivo in a bipolar configuration and consistently produced a contiguous lesion of the necessary dimensions with a 20 mm electrode separation and a heating protocol of 30-second ramp followed by 120 seconds at 80°C. To ensure in-vivo consistency, the optimal electrode gap recommended is approximately 15 mm and optimal total lesion time is 180 seconds at 85°C. PROCEDURE (Bipolar mode)
1. Consider patient bowel prep night before to improve visualization.
2. Consider caudal anesthetic or IV sedation.
3. Image sacrum from AP view with craniocaudal adjustment optimized for L5S1
intervertebral disc space.4. In patients without L5-S1 fusion identify groove at base
of S1 SAP and sacral ala.
5. Identify the lateral foraminal walls of the S1, S2, and S3 spinal foramen. The
posterior sacral foramenal aperture (PFSA) for the relevant spinal nerve is typically
at the ‘inflection” point of these lines.
6. Electrode #1
a. Identify the groove between sacral ala and S1 superior articular process (SAP).
b. Anesthetize skin over target. Deeper local indicated if sedation/caudal not used.
c. Gripping the central hub (colored), advance the Nimbus MEE down the beam to
the posterior aspect of the groove of at the base of S1 SAP.
d. Confirm placement in groove with ipsilateral oblique view.
7. Electrode #2
a. Identify a position approximately 15 mm caudal to initial electrode, slightly lateral
to a craniocaudal line connecting the inflection points of the S1, S2, and S3 lateral
foramenal walls.
b. Anesthetize skin over target. Deeper local indicated if sedation/caudal not used.
c. Gripping the central hub (colored), advance the Nimbus MEE down the beam to
dorsal sacral bony endpoint.
d. Orient the white stripe on main hub of electrode #1 and #2 to face on another.
Tines should deflect towards each other to create widest possible lesion.Deploy
tines. Rotate helical spin collar clockwise until fully advanced. A distinct tactile
click will be appreciated with full engagement.
e. Check a lateral or contralateral oblique “safety view” to ensure that the tines are
on the dorsum of sacrum and not into a sacral foramen / caudal epidural space.
A lateral view may be used as an alternative.
f. Motor and/or sensory stimulation are not mandatory but available if desired.
g. With tines fully deployed, inject local anesthetic of choice if desired.
h. Initiate heat cycle (30-second ramp 150 seconds at 85 C.). Note: RF generator
needs to be in bi-polar mode.
8. Subsequent lesions
a. Retract tines of both electrodes. Remove the most cranial electrode leaving the
caudal electrode in place.
b. Rotate the caudal electrode 180 degrees to redirect tines. (Some may choose to
reposition this electrode 1-3 mm caudal prior to redeploying the tines.)
c. Place the electrode that was removed (Electrode #1) approximately 15 mm
caudal to electrode that stayed in position (Electrode #2) along a craniocaudal
line slightly lateral to the PFSA (see #6).
d. Rotate the white stripes on the main hub to again face on another.
e. Deploy tines as above.
f. Obtain lateral, or contralateral oblique safety view as above.
g. Repeat stimulation and local anesthetic injection if desired.
h. Repeat lesion heat cycle.
9. Repeat the cranial to caudal “leap-frogging” until desired craniocaudal length of
lesion is obtained. Standard practice supports creating a strip lesion from sacral ala
to the level of S3. Some practitioners omit the S3 level. The extent of lesion is at the
discretion of the practitioner. Note: In the event of L5/S1 fusion the cranial aspect of
the lesion should start cranial to the S1 PFSA as allowed by post operative anatomy.
1. Consider patient bowel prep night before to improve visualization.
2. Consider caudal anesthetic or IV sedation.
3. Image sacrum from AP view with craniocaudal adjustment optimized for L5S1intervertebral disc space.
4. In patients without L5-S1 fusion identify groove at base of S1 SAP and sacral ala.
5. Identify the lateral foraminal walls of the S1, S2, and S3 spinal foramen. The posterior sacral foramenal aperture (PFSA) for the relevant spinal nerve is typically at the ‘inflection” point of these lines.
6. Electrode #1
a. Identify the groove between sacral ala and S1 superior articular process (SAP).
b. Anesthetize skin over target. Deeper local indicated if sedation/caudal not used.
c. Gripping the central hub (colored), advance the Nimbus MEE down the beam to the posterior aspect of the groove of at the base of S1 SAP.
d. Confirm placement in groove with ipsilateral oblique view.
7. Electrode #2
a. Identify a position approximately 15 mm caudal to initial electrode, slightly lateral to a craniocaudal line connecting the inflection points of the S1, S2, and S3 lateral foramenal walls.
b. Anesthetize skin over target. Deeper local indicated if sedation/caudal not used.
c. Gripping the central hub (colored), advance the Nimbus MEE down the beam to
dorsal sacral bony endpoint.
d. Orient the white stripe on main hub of electrode #1 and #2 to face on another.
Tines should deflect towards each other to create widest possible lesion.Deploy tines. Rotate helical spin collar clockwise until fully advanced. A distinct tactile click will be appreciated with full engagement.
e. Check a lateral or contralateral oblique “safety view” to ensure that the tines are on the dorsum of sacrum and not into a sacral foramen / caudal epidural space. A lateral view may be used as an alternative.
f. Motor and/or sensory stimulation are not mandatory but available if desired.
g. With tines fully deployed, inject local anesthetic of choice if desired.
h. Initiate heat cycle (30-second ramp 150 seconds at 85 C.). Note: RF generator
needs to be in bi-polar mode.
8. Subsequent lesions
a. Retract tines of both electrodes. Remove the most cranial electrode leaving the caudal electrode in place.
b. Rotate the caudal electrode 180 degrees to redirect tines. (Some may choose to reposition this electrode 1-3 mm caudal prior to redeploying the tines.)
c. Place the electrode that was removed (Electrode #1) approximately 15 mm caudal to electrode that stayed in position (Electrode #2) along a craniocaudal line slightly lateral to the PFSA (see #6).
d. Rotate the white stripes on the main hub to again face on another.
e. Deploy tines as above.
f. Obtain lateral, or contralateral oblique safety view as above.
g. Repeat stimulation and local anesthetic injection if desired.
h. Repeat lesion heat cycle.
9. Repeat the cranial to caudal “leap-frogging” until desired craniocaudal length of lesion is obtained. Standard practice supports creating a strip lesion from sacral ala to the level of S3. Some practitioners omit the S3 level. The extent of lesion is at the discretion of the practitioner. Note: In the event of L5/S1 fusion the cranial aspect of the lesion should start cranial to the S1 PFSA as allowed by post operative anatomy.
Figure 7 – Continuum technique. First electrode pair – electrode #1 placed at base of S1 superior articular process. Electrode #2 is placed ~15 mm caudal along a line ≤10 mm lateral to the PFSA.
Figure 8 – Ipsilateral oblique view of first electrode pair.
Figure 9 – Second electrode rotated to direct tines caudal. First electrode is placed ~15 mm caudal to second along line running ≤10 mm lateral to PFSA.
Figure 10 – Lateral view electrode pair.
Figure 11 – Electrode #2 positioned ~15 mm caudal to electrode #1 continuing along the line running ≤10 mm lateral to PFSA.
Figure 12 – Representative contralateral safety view showing electrodes on dorsal aspect of sacrum Tines deployed directed toward the paired electrode.
Figure 5 – Representative sacral axial section demonstrating tissue change two weeks after continuum. Lesion in-vivo conforms to ex-vivo prediction.
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