Anesthesiology | Interventional Pain Medicine
Assistant Professor — University of Toronto
Interventional Pain Physician — Afiya Spine & Pain Institute
Staff Anesthesiologist — Scarborough Health Network
A lateral branch block is an injection used to test whether pain is coming from the back part of the sacroiliac joint region.
The sacroiliac joint sits between the sacrum and the pelvis. Pain from this area can be difficult to confirm from imaging alone. A lateral branch block helps test this area by temporarily numbing the small nerves that carry pain signals from the back of the sacroiliac joint.
If your usual pain improves during the numbing window, that suggests these nerves may be carrying a significant part of your pain. This helps determine whether you may be a candidate for sacral radiofrequency ablation, which is a longer-lasting treatment aimed at the same nerves.
This procedure is done to help confirm whether the sacroiliac joint region is a significant source of your pain. It is a test procedure. The goal is not long-term pain relief from the block itself, but to collect useful information about where your pain is coming from.
If the block provides meaningful temporary relief, this may support proceeding to sacral radiofrequency ablation.
You usually do not need to fast for this procedure unless you are specifically told otherwise.
The injection is quick, but the full visit includes check-in, assessment, preparation, and recovery.
Most patients should expect the full appointment to take approximately 60 to 90 minutes, although this can vary depending on clinic flow that day.
The procedure itself usually takes approximately 5 to 10 minutes. When X-ray time is available, this can often be done immediately after your consultation.
In some cases, a sacroiliac joint steroid injection may also be performed. For that part of the procedure, contrast dye is used to help locate the sacroiliac joint and confirm that medication is being injected into the joint.
Most patients describe:
Because the needle is small and the procedure is quick, discomfort is typically mild and short-lived.
The numbing medication typically lasts up to 6 hours. This is the most important part of the test.
During this time, pay attention to whether your usual pain is better when you do the activities that normally bring it on. This may include walking, standing, bending, stairs, sitting, or other movements that usually reproduce your pain.
Do not simply go home and rest for the full numbing period. The test is most useful when you gently test your usual painful activities in a safe and controlled way.
Do not drive until the numbing medication has worn off, which may take up to 6 hours. This is because of possible altered sensation. Arrange a driver or wait until the numbing has fully resolved.
You may walk and do normal light activity after the procedure. Avoid unusually strenuous activity for the rest of the day.
Log your pain level out of 10 every hour for 6 hours after the injection.
Also write down:
Be accurate about how much better, or not better, you felt. Even partial improvement is useful information.
Bring your pain log to your follow-up appointment. Your pain log helps determine what should happen next.
The next step depends on how much relief you had during the numbing window.
If your usual pain clearly improves for the expected duration of the numbing medication, this supports the sacroiliac joint region as a likely pain source. In that case, we may discuss sacral radiofrequency ablation. This is a longer-lasting procedure that treats the same pain-carrying nerves. It is also performed in our clinic, usually takes approximately 20 to 30 minutes, and can provide pain relief for up to 6 months.
If your pain does not improve, that is still useful information. It suggests that these nerves may not be the main source of your pain. In that case, we may consider other possible pain sources, review or order imaging, or discuss a different diagnostic or treatment plan.
Some patients have more than one source of pain. A lateral branch block may help identify sacroiliac-region pain, but it may not explain all of your symptoms.
A lateral branch block is therefore not simply a treatment. It is a test that helps guide the next decision.
Keep the injection sites dry for 24 hours. Remove bandages after 24 hours.
Over-the-counter pain relievers are usually fine after the numbing window has closed.
Lateral branch blocks are very low-risk procedures when performed with X-ray guidance and sterile technique. Serious complications are very rare.
The most common issues are mild soreness, a small bruise, temporary lightheadedness, or a short-term increase in pain. These usually settle on their own.
Uncommon risks include bleeding under the skin, temporary numbness from the numbing medication spreading to nearby nerves, medication entering a small blood vessel, or an allergic reaction to a medication used during the procedure.
Serious complications such as infection, significant bleeding, or nerve injury are extremely uncommon.
Seek medical attention if you develop fever greater than 38.5°C, worsening redness or swelling at the injection site, drainage from the injection site, new leg weakness, or severe worsening pain that does not settle.
The procedure itself, including the clinic visit and use of X-ray guidance, is covered by OHIP.
OHIP does not cover the cost of medications used or prescribed, such as local anesthetic, steroid medication, or other medications. These costs may be covered by private insurance.
The medication cost is usually in the range of $25 to $100, depending on the extensiveness of the procedure, but this may vary.
Unless you are told otherwise, you may usually take your regular medications. Blood thinners require separate review.
Tell us before the procedure if you take blood thinners. We may need to adjust them before the procedure to reduce bleeding risk. This will be reviewed with you in advance.
Tell us before the procedure if you have ever had an allergy or serious reaction to contrast dye, local anesthetic, steroid medication, or antiseptic skin-cleaning solution.
These links are optional. They are provided for patients who want to read more about sacroiliac joint pain, diagnostic injections, and sacral radiofrequency ablation.
Afiya Spine & Pain Institute
301 - 15 Wellesley St W, Toronto, ON M4Y 1G1
Phone: 416-413-7999 | E-Fax: 416-641-4520
For questions or concerns after your procedure, contact the clinic.