Background
For convenience purposes, the spine can be divided into an anterior (front) section and a posterior (back) section, that work together to maintain proper function. The anterior section contains the vertebral bodies and the intervertebral discs and is
the primary load-bearing part of the spine. The posterior portion, which contains the zygapophyseal (Z or facet) joints, lamina, and the transverse and spinous processes, controls the motions of the spine and provides for all musculotendonous insertions on the spine. In the low back, the usual location of injury is the intervertebral disc which is usually injured by bending forward while twisting to pick something up, often with an outstretched arm. The posterior section of the spine accounts for about 20-25% of low back pain and over half of chronic neck pain and can be injured through repeated bending, a hyper-extension (bending back to far) injury such as “whiplash”, or through “wear and tear” of the facet joints, a problem which can happen with age.
The facet joints are small joints in the back of the spine that form a connection between each vertebrae. Each vertebrae is a part of four facet joints, two on the upper or superior surface, and two on the lower or inferior surface. These joints are diarthroidal which means that there are only two surfaces rubbing together, like the hip joint and the finger joints. The inner surface of each joint contains articular cartilage which can be injured though a single, high-velocity injury, or more commonly, slowly be injured over time, a “wear and tear” problem known as osteoarthritis. These joints, as with most joints are surrounded by a soft tissue capsule which holds the fluid in the joint. As the joint capsule becomes swollen from fluid collecting in the joint, which is typical with osteoarthritis, the joint capsule begins to produce discomfort and frequently muscle spasm. As well, the injury to the cartilage in the joint and often the underlying bone also directly produces discomfort. The capsule, cartilage, and facet bone are all innervated from nerves arising from the medial branches of the dorsal rami. These nerves transmit pain upward, through multiple connections, to the brain, causing us to sense pain.
All of the procedures discussed here are to reduce or eliminate pain from the posterior spine and more specifically the Z-joint.
How does a facet or Z-joint injection work?
Zygapophseal (or facet) joint injections are a potentially therapeutic procedure. A small amount of local anesthetic is usually injected into the joint which can help provide transient relief. A small amount of corticosteroid is usually injected in addition to the local anesthetic creating a longer term therapeutic effect. Corticosteroids are potent anti-inflammatory medications. Reducing the inflammation in the joint will decrease the amount of joint effusion and therefore decrease distention of the capsule, which will often offer longer lasting pain relief. It is possible that this injection will block the pain long enough to allow the body to begin the process of repairing itself.
The chief effect of a Z-joint injection is to reduce pain, but the effect is not always long lasting and differs from person to person. Most patients will receive good relief for some weeks or months after injection.
Your physician will probably request that you participate in physical therapy to mobilize the affected joints and begin strengthening and stabilizing the affected area.
How are these injections administered?
With some of these procedures, you may be asked to stop medications that thin your blood. However, current medical advice for most of these procedures, is that the risk of stopping these medications is worse than the risk of having a bleeding complication from the procedure. If you are on medications that thin your blood, such as aspirin, warfarin, heparin, enoxoparin, ticlopidine, clopidogrel, diabigatran, dipyridamole, prasugrel, or any other blood thinning agents such as anti-inflammatory agents, please let your physician know at least one week prior to the procedure. Do not take your regular pain medications for six hours before or after the procedure. You should continue to take your routine medications (such as high blood pressure and diabetes medications) before the procedure. If you are on antibiotics please notify your physician, he may wait to do the procedure. If you have an active infection or fever we will not do the procedure.
These procedures (with the exception of radiofrequency neurotomy) typically do not require sedation. When receiving IV sedation you should not eat or drink anything (except your routine medications) for four hours prior to the procedure; this again, lowers the chance of having complications. You are expected to have a ride to and from the procedure. The procedure usually takes about fifteen minutes though you may be at the facility for as long as 45min. Once you arrive to the facility, if having sedation, a nurse will place an IV in your arm. After this has been done and the doctor is ready, you will be taken to the room and positioned on the table.
A spinal needle will be advanced to the appropriate location using bones as landmarks. Your physician will use fluoroscopy (a live x-ray) and other technical aids to ensure that the needle is in the right place.
For Z-joint injections, once the needle is in the joint, a small amount of contrast will be injected to confirm the appropriate location of the needle tip and to evaluate the competence of the joint capsule. After making sure that the needle is in the joint, the doctor will inject the solution of local anesthetic and steroid. The doctor may inject more than one joint depending on the symptoms you present with and the physical examination performed by the doctor.
What are the risks of these procedures?
With any operation or injection procedure there are risks. In the case of these procedures, the risks are small. These procedures are performed on the posterior spine and are thus away from the neuroaxis (spinal cord, etc). This dramatically reduces the risk of serious problems.
With Z-joint injections, the most common problems side-effect is a temporary increase in pain. It occurs in about less than one per cent of patient’s undergoing this procedure and appears to be related to the volume of substance injected into the joint. On occasion, the joint can be over-filled and this can cause a rupture of the joint capsule. This will normally heal with time. Your physician will take care to inject the appropriate amount of solution.
If you are allergic to one of the additives in the steroid solution you may experience a hot flush or develop a rash. However, this should get better within a few hours or days.
As with any injection through the skin, it is possible for bacteria to gain entry causing an infection. Your physician will use sterile technique and the risk of infection with these procedures is very small.
Sometimes a patient's blood pressure falls at the time of the injection. If so, the doctor will use the venous canula inserted before the epidural procedure commenced so that intravenous fluids or medication, if necessary, can rapidly control the blood pressure.
Some side-effects may occur as a result of the corticosteroid administered. If you have diabetes, you may notice that your blood sugars are elevated for 2-3 days following the procedure. If they are, usually only monitoring is required. However, if you are concerned, call your physician. Corticosteroids may also cause fluid retention, weight gain, alterations in skin pigmentation at the site of injection, fluid and electrolyte alterations and/or gastrointestinal upset. These side-effects are usually not serious.
How long does it take?
These procedures take 10 minutes to one hour depending on the procedure and number of levels involved. The patient will usually be in the recovery room for 5-10 minutes after the procedure.
Repetitions
Any of these procedures may be repeated. In general, however, if the effect of a Z-joint injection wears off and the patient has adequately participated in a physical therapy program after the procedure, it is more reasonable to proceed with medial branch blocks and ultimately radiofrequency ablation.
