A Quick Reference Guide to Spinal Injections in the Management of Low Back Pain
Interventional medicine has been a longstanding staple in the management of acute, subacute and chronic low back pain. After consulting with a few different spine centers, roughly 30% of patients receive an injection in the management of their spine pain. Patients and health care providers throw out terms like “epidural”, “rhizotomy”, “blocks” and “cortisone” to describe what they received or what a patient is to receive. They often ask questions like how many they can receive or how often will the injection last? I developed this quick reference guide to clean up any misconceptions there are to receiving injections as well as describe when a particular type of injection is appropriate.
Epidural Steroid Injections
Interlaminar Injection
Epidural steroid injections are very common in the continuum of care of back pain. The main goal is to administer steroid medication as close to the irritated tissue as possible. Epidurals are used in patients with radicular signs and symptoms, spinal stenosis, and discogenic pain. There are three types of epidural injections: caudal approach, an interlaminar approach, and a transforaminal approach.
Caudal Approach
The caudal approach is often times the least specific route for steroid administration. It often reaches multiple levels. In the caudal approach, an injection occurs through the sacral hiatus, at the most inferior aspect of the sacrum proximal to the coccyx. This procedure generally has the lowest risk. In older patients, the tissue in the hiatus may become fibrotic and is often difficult for the medication to pass through this thickened area.
Interlaminar Approach
Most commonly performed at L4-5 and L5-S1, the interlaminar approach is where a needle is inserted under fluoroscopy between each lamina of the vertebrae which is located on the posterior aspect of the spine. Patients will often lie prone with a pillow under their stomach to slightly flex the lumbar spine. The interlaminar approach is less specific and medication does not disperse well to the ventral portion of the epidural space. It is often utilized to address one or more levels that are the potential sources of pain. There is an increased risk for a dural puncture compared to the caudal approach. Patients who have had surgery in the past may have additional scarring in the area making it difficult for distribution of medication. Lastly, the procedure can be more difficult in patients with severe degenerative disc disease since there is less space between the vertebrae.
Transforaminal Injection
Transforaminal Injection
A transforaminal approach is most often used in patients with a confirmed disc herniation with a known nerve root involvement. This allows for better access of medication to reach the nerve root. It reaches the ventral dural space where disc pathology often occurs. The procedure is completed with the patient in the prone position. A needle is inserted into the superior foraminal space, below the adjacent pedicle. This technique may be used when patients are at higher risk of a dural puncture (those who have had previous back surgery, scarring, or decreased epidural space). Below is an example of a right sided transforaminal injection.
Medial Branch Block
Medial branch blocks are used for the treatment in facet related spine pain. The medial branch is an afferent nerve that branches from the posterior primary ramus of each spinal nerve. It innervates the facet joint and capsule at the level of the facet joint and the level immediately below it. Because of this anatomy, a medial branch block will require at least 2 separate injections to address 1 single lumbar facet joint. The medial branch block can not only be used as an intervention but also a diagnostic tool. Often times a medial branch block will be completed to diagnose the level of dysfunction. There is a high false positive rate with these injections so often times two separate injections will be completed before a therapeutic injection occurs. A positive response requires at least a 70-80% improvement in symptoms with the activities that caused the patient’s pain. The needle insertion in the procedure is considered at the “eye” of the “scotty dog” on an oblique angle. There are generally no serious side effects to this approach. Below is a three level medial branch block on the right at L3, L4, and L5.
Medial Branch Block
Radiofrequency Ablation (RFA) or Rhizotomy
For patients who have received 2 successful diagnostic medial branch blocks, an RFA is an appropriate technique for continued relief. In simple terms, an RFA is the burning of the medial branch. Pain relief from an RFA may last up to 12 months for patients with facet related pain. In this technique the needle is inserted similar to that of a medial branch block but then is heated to 80-90 degrees Celsius for approximately 1 minute. Patient may continue to feel pain and irritation for a few days after the procedure. As mentioned symptom relief may last up to 12 months but the nerve will regenerate and the procedure can be repeated. Imaging for an RFA will look very similar to that of a medial branch block.
These are the most common interventional procedure completed for the management of spine pain. Other techniques such as stellate ganglion block and spinal cord stimulators may be additional procedures utilized in the management of chronic but are beyond the scope of this article. Specific facet injections may also be completed however the success rates for pain reduction seem to be better with the medial branch blocks and the RFA’s. For more detailed information on these procedures please view the listed reference below. Most information from this post came from the article listed below. Lastly, a special thank you to Dr Matt Perkowski for reviewing the details of this post and providing the pictures for educational purposes.
Reference:
Iannuccilli JD, et al. Interventional Spine Procedures for Management of Chronic Low Back Pain – A Primer. Semin Intervent Radio. 2013;30: 307-317.