These are also called selective nerve root blocks or sleeve injections
The sacroiliac joint is a small joint in the region of the low back and buttocks where the pelvis actually joins with the spine. If the joints become painful they may cause pain in the low back, buttocks, abdomen, groin and legs.
A sacroiliac joint injection serves several purposes. First, by placing numbing medicine into the joint, the amount of immediate pain relief experienced will help confirm or deny the joint as a source of pain.
An IV will be started so that relaxation medication can 
be given. The patient is placed on the x-ray table on their stomach in such a way that the physician can best visualize these joints in the back using x-ray guidance in the operating room.
This skin on the low back is cleaned with alcohol or a scrubbing solution. Following this, the physician numbs a small area of skin with numbing medicine. This medicine stings for several seconds.
After the numbing medicine has been given time to be effective, the physician directs a very small needle, using x-ray guidance into the joint. A small amount of contrast (dye) is injected to insure proper needle position inside the joint space. Then, a small mixture of numbing medicine (anesthetic) and anti-inflammatory (steroid) is injected. One or both joints may be injected depending on location of the patients usual pain.
An IV will be started so that relaxation medication can be given. The patient is placed on the x-ray table on their back for a cervical block and on their stomach for a lumbar block in the operating room.
This skin on the neck or the skin on the low back is scrubbed using alcohol. Next, the physician numbs a small area of skin with numbing medicine.
After the numbing medicine has been given time to be effective, the physician directs a very small needle, using x-ray guidance to the area of the sympathetic nerves.
A small amount of contrast (dye) is injected to insure proper needle position. Then, a small mixture of numbing medicine (anesthetic), is injected.
The patient will be monitored for 15-30 minutes.
Instructions
The patient can eat a light meal within a few hours before the procedure.
If a patient is an insulin dependent diabetic, they must not change their normal eating pattern prior to the procedure.
Patients may take their routine medications. (i.e. high blood pressure and diabetic medications).
Post-procedure Instructions
You were given a number of medications during the procedure. These sometimes include sedatives, narcotics, local anesthetics, steroids, and other medications. Any of these drugs or procedure itself, sometimes can cause side effects, including drowsiness, temporary numbness, weakness and soreness.
What To Do After the Procedure?
Rest for a few hours and use assistance if needed. Resume activity as tolerated, but do not overdo. Resume regular diet.
Restrictions:
Do not drive or operate machinery for at least 12 hours. Do not make important decisions for 12-24 hours after treatment. Walk with assistance as long as numbness, weakness, or drowsiness is present.
Notify If You Have:
Excessive or abnormal bleeding / persistent chills or fever over 100°F.If there is a major change in pain pattern or level.
Emergency:
Few Other Things:
Take your usual medication. Apply ice massage as instructed; may use heat if ice is intolerable. If IV site becomes painful, place warm towels on the site for 20 minutes2-3 times / day