The facet joints are the joints that connect each vertebra (the bony segments of the spine) to each other. Just like other joints in the body the facet joints have cartilage covering which allow gliding of the surfaces with motion. As arthritis set in the human body, this cartilage may degenerate and produce pain. The capsular covering may also be a source of pain. Research studies have shown that nerve endings exists on these facet joints that may produce back pain with radiation to the buttocks or even the thigh and the knee. However, it is uncommon for the pain to radiate down the leg, past the knee. Since the pain may radiate down to the leg, this could be confused with radiculopathy or a herniated disc.
When the source of the pain can not be found, your physician may suggest a facet joint block injection. This injection is used as a diagnostic as well as a therapeutic injection. This may isolate and confirm the specific source of pain. The medication injected consists of a numbing medication (anesthetic) as well as an anti-inflammatory medication like steroids. If the pain is eliminated after the injection, it is reasonable to assume that the pain generator in the spine is the facet joint. The anti-inflammatory medication may resolve this pain. This procedure is often repeated several times in a year period to completely resolve the symptoms.
The procedure is performed under sterile conditions to minimize the risk of infection. Initially, the surrounding skin is anesthetized using a small needle followed by a larger needle that reaches the area of interest. Fluoroscopy (X-ray images produced on a monitor) guidance is used to locate the exact site prior to injection. This is performed while the patient is awake so the physician can get feedback from the patient. After the needle is placed in the desired position, anesthetic and steroidal medications are injected in the area. The needle is removed and the patient is released from the procedure room. Patients are observed for a short period and are released home on the same day.
Patients should keep a diary regarding the response to pain relief. The diary should include information one hour, two hours, three hours, 8 hours, and 24 hours after the procedure. This will provide information regarding the success of the procedure and will guide your surgeon regarding further diagnostic and theraputic recommendations.
As with any procedure or test, risks, benefits, and alternatives should be evaluated. Risks are rare but include infection and nerve root injury.