Medial Branch Blocks
Performed by Top Pain Management Doctors in San Antonio, Texas
It’s been approximated that between 60-80% of the US population can expect to experience low back pain at some time point during their lifetime, which is one of the most common ailments seen in medical clinics1. One third of patients who seek medical care for low back pain have syndromes involving joints of the spine1, 2. An estimated 15% present with low back pain secondary to disease of the facet joint in particular, termed facet arthropathy3. Facet arthropathies can also occur higher in the spinal cord, causing neck pain and headaches1. The exact cause of facet arthropathies is unknown; however they have been highly associated with arthritis, age-related degeneration and injury1, 3, 8.
Facet arthropathy classically presents with pain in just one side of the neck or lower back, which may radiate to the upper or lower extremities, respectively1. The spine consists of multiple facet joints; however identification of an arthropathy can often be made on the basis of pain in conjunction with local tenderness in the muscles overlying the joint2. Back extension and rotation toward the affected, or painful side tend to exacerbate the pain1.
Traditional treatment of facet arthropathies of the head and neck consisted of conservative therapy, such as anti-inflammatory medications and physical therapy. If ineffective, these modalities would followed by anesthetic/corticosteroid injection into the facet joint, termed a facet injection1. The medication injected into the joint usually consists of an anesthetic (pain reliever) combined with a corticosteroid (anti-inflammatory) 3. In recent years, facet injections have been largely replaced by injections directly into the medial branch nerves which innervate the facet joint, termed a medial branch block (MBB). Both procedures are designed to numb the nerves within a facet joint in an effort to alleviate pain4. Both procedures accomplish the same goals and are today used in the treatment of facet arthropathies of the neck and back. One recent study reported pain relief in 80% of patients with lumbar facet arthropathy within 36 weeks of treatment1.
Today, facet injections/MBB’s are used in both a diagnostic and treatment capacity3, 8. The injections can be used for treatment as described, but they can also serve as a minimally-invasive method for confirming the source of pain in a facet arthropathy before more invasive and long-term surgical procedures (such as radiofrequency ablation, or RFA) are considered. Facet injections/MBB’s are only temporary; pain typically returns after 6-12 months2. The procedure can be repeated, however, with the same success and equivalent safety.
The spinal column consists of 33 stacked vertebrae divided into five groups; they include (1) cervical (neck) vertebrae, (2) thoracic (upper back) vertebrae, (3) lumbar (lower back) vertebrae, (4) sacral (pelvic) vertebrae, and (5) the fused coccygeal vertebrae, or tailbone6. Each vertebra has a hollow center, and when stacked together, they form a protective channel for the spinal cord.
Vertebrae are connected to one another by two facet, or zygapophyseal, joints located on either side of the bone. Facet joints connect the superior articular process, or upward-directed portion of one vertebra with the inferior articular process, or downward directed portion of the vertebral bone above it6. When combined, these two vertebrae, along with the inter-vertebral disc cushioning in between the bones, form a spinal segment. Facet joints assist with spinal weight bearing, prevent the sliding of vertebral bones on top of one another, and limit spinal extension and rotation6. Facet joints are innervated by medial branch nerves stemming from the dorsal rami supplying each spinal segment. The dorsal rami are large bundles of nerves projecting from the spinal cord which carry motor signals to, and sensory information from, the posterior of the body. Each facet joint is dual-innervated by medial branch nerves from the spinal levels above and below3.
The facet joints and medial branch nerves are common targets for injection and/or RFA in chronically painful facet joint arthropathies3, 5. Pathologic cervical facet joints may refer pain to the head, neck and shoulders. Thoracic facet joints may radiate pain to the upper back, middle back, and chest wall, and lumbar facet joints may refer pain to the back, buttocks, and thighs7.
Facet joint arthropathies are diagnosed clinically; that is, problems with the joint aren’t easily visualized with radiologic imaging1, 2, 8. Diagnostic injections of the facet joint or the medial branch nerves which supply it can help to confirm a diagnosis, as strongly evidence by multiple systematic reviews of medical research8. Diagnostic injection of a facet joint is only indicated for patients who’ve been experiencing severe pain for more than four weeks, and for whom other conservative treatment options have been exhausted3.
When guided by physician suspicion, fluoroscopically guided facet joint injections are considered the ‘gold standard’ for determining diagnostically whether or not a facet joint is the source of back, neck or extremity pain3. Fluoroscopy is a type of real-time x-ray which helps pain specialists visually guide the needle and ensure that it reaches the correct location. During diagnostic injections, the medial branch of the dorsal rami at the suspected spinal level is targeted; alternatively an injection can target the joint itself, termed an intra-articular block, but only for larger facet joints at the lumbar level3. A diagnostic block can have three outcomes4:
- Following the block, the pain is relieved and continues to improve over the course of a few days; this indicates that the facet joint was indeed the source of the pain and that the injected medication had a lasting effect.
- Following the block, the pain is relieved for a short period of time and then returns; this indicates that the pain may have come from the joints, but that the medication didn’t take effect.
- Following the block, the pain remains, indicating that the targeted joint is not the source of chronic pain and that further investigation is needed.
If pain relief is long-lasting, a facet injection/MBB therapy can be continued for several rounds as treatment4. If relief is short-lived, surgical interventions such as RFA may need to be explored. RFA has been shown to be effective for the treatment of cervical and lumbar radicular pain; one review reported pain relief averaging 50% for half of study participants2, 5.
Facet injection/MBB procedures differ slightly depending on from which area of the spine the pathology originates.
Cervical Facet Joints3
For MBB injection of a cervical facet joint, at patient is draped and positioned lying prone (flat on the abdomen) on a procedural table. The neck is rotated, so that the side affiliated with the source of the pain is against the table. The side of the neck facing up is then sterilized before the fluoroscope is positioned. A needle is inserted through the skin, and guided fluoroscopically until contact is made with the outer membrane of the bone surrounding the facet joint. The needle is then adjusted to the side to reach the medial branch nerve. Once contact is made, medication is distributed through the needle to the joint.
Lumbar Facet Joints3
The lumbar facet joint injection procedure is similar to that of the cervical facet joint injection, although the injection can target the medial branch nerve OR be directed into the joint itself (intraarticular). For a MBB injection, the patient is positioned prone on the procedural table, draped, and the injection site is sterilized. Lumbar facet joints are innervated by medial branches from two levels, thus two MBB’s are required. A needle is inserted and guided fluoroscopically to the bone of the joint, and subsequently repositioned into the adjacent medial branch nerve for injection. For an intraarticular injection, the patient is prepared in the same manner as before. The needle is inserted and fluoroscopically guided not the medial branch nerve, but instead through the capsule of the facet joint for local delivery of the medication.
Following the procedure, the area of insertion is cleaned and bandaged, and the patient is monitored for a short time before being released4. Following the procedure, it is recommended that the patient not drive themselves home. The patient should also be instructed to be on the alert for significant bleeding, swelling, drainage, or increased pain at the injection site4.
Complications associated with facet injections/MBBs are related to needle placement and drug delivery8. With regard to needle placement, possible complications include puncturing of the dura, or protective sheath of the spinal cord, neural tissue trauma, and joint capsule rupture. Complications of drug delivery generally involve inadvertent injection into a blood vessel, which can cause systemic steroid side effects like elevated blood pressure, elevated blood sugar (glucose), flushing, and fainting. It is also fairly common to experience pain or irritation at the treatment site for up to two weeks2. Finally, infection and bleeding are potential complications of any medical procedure in which the skin is perforated8.
Adverse effects of facet injections/MBBs are uncommon, estimated at approximately 1%2. The success of the procedure is dependent on accuracy of the injection, which is why real-time fluoroscopy with contrast injection is recommended to increase the diagnostic and therapeutic value of the procedure, while avoiding possible complications.
Facet joint injection/MBB can help pain specialists diagnose facet joint arthropathies, and focus treatment for associated pain to specific, affected spinal segment3. With proper patient selection, facet injections/MBBs can provide temporary pain relief during symptomatic management of facet arthropathy-associated chronic pain. While research and evidence supporting the diagnostic use of facet injections/MBBs is very strong, research and evidence supporting the therapeutic use of the procedure is still sparse8. Further investigation may yet reveal additional insight as to the applicability of facet injections/MBBs in the treatment of facet joint arthropathies and other chronic pain conditions.
1 Zhou, Y. (2008). Principles of Pain Management. Bradley: Neurology in Clinical Practice, 5th Ed. MD Consult Web site, Core Collection.
2 Mehta, P.; Rathmell, J. (2011). Interventional Pain Therapies. Miller: Basics of Anesthesia, 6th Ed. MD Consult Web site, Core Collection.
3 Williams, K.; Park, A. (2007). Injection Studies. Canale & Beaty: Campbell’s Operative Orthopaedics, 11th Ed. MD Consult Web site, Core Collection.
4 ExitCare. (2008). Facet Block. Patient Care. MD Consult Web site, Core Collection.
5 Niemisto L, Jousimaa J, Hurri H, Kalso EA, Malmivaara A. Radiofrequency denervation for chronic neck pain (Protocol). Cochrane Database of Systematic Reviews 2010, Issue 7. Art. No.: CD008573. DOI: 10.1002/14651858.CD008573.
6 Hansen, J. (2010). Back. Hansen: Netter’s Clinical Anatomy, 2nd Ed. MD Consult Web site, Core Collection.
7 Boswell, M.; et al. (2007) A Systematic Review of Therapeutic Facet Joint Interventions in Chronic Spinal Pain. Pain Physician. Vol. 10, 229-253.
8 Datta, S.; et al. (2009) Systematic Assessment of Diagnostic Accuracy and Therapeutic Utility of Lumbar Facet Joint Interventions. Pain Physician. Vol. 12, 437-460.