Historically, epidural steroid injections have provided anesthetic relief for surgical procedures and childbirth. More than 60 years ago, it was recognized that the therapeutic benefits of such injections could be extended to the treatment of patients with low back pain. However, there is growing evidence that these anesthetic techniques are not directly applicable to the patient with low back pain. In this paper, we will discuss the indications, techniques of administration, and diagnostic and therapeutic benefits of spinal injections for low back pain.
Indications For Selective Spinal Injection
The typical epidural steroid injection can bathe several intervertebral levels, thereby resulting in a comprehensive anesthetizing effect on the spine. However, for patients with low back pain, a more localized injection is often helpful in determining the etiology of the patientís pain, and thus clarifying the diagnosis. Just as internal derangement of the knee is no longer considered an acceptable diagnosis for patients with knee pain, lumbago should no longer be acceptable as a diagnosis for low back pain. Back pain may emanate from many anatomic structures, such as facet joints, sacroiliac joints, hip joints, discs, or the nerve roots.1
To address the problem of pain localization, as well as to insure that injections are in the desired location, spinal injections should be done under fluoroscopy. Fluoroscopy allows accurate placement of the injection into any anatomic structure suspected to be the source of the patient's pain. White et al.2 have demonstrated that experienced anesthesiologists missed the epidural space 25 percent of the time when they performed epidural injections without the benefit of fluoroscopy. The reasons for this may include decreased interlaminar space, as commonly seen with spinal stenosis, postoperative scarring, obesity, and previous spinal fusions.
Techniques Of Administration And Diagnostic Benefits
Since January of 1991, the Carolina Spine Institute has performed over 4,000 selective fluoroscopically-guided spinal injections.3 All injections are done in a spinal injection suite specifically designed for the use of fluoroscopy and equipped with a digital C-arm fluoroscope which provides high image magnification in detail. Prior to patient injection, an examination by a physician, and often a spinal physical therapist, is made to assess the most likely sources of pain. The clinical assessment is correlated with a review of electrodiagnostic information and any pertinent imaging studies, particularly CAT scans and MRI scans, to make a presumptive diagnosis of the patient's pain generator. The patient is then taken under fluoroscopy. The skin is anesthetized with 1% Xylocaine and injections are made into the presumed pain generators. Needle placement is usually verified by the injection of omnipaque 240 contrast dye, followed by an injection of 1% Xylocaine in a steroid solution, usually Depo Medrol. The patient is then taken from the fluoroscopic table to an adjoining waiting room, where a post-block examination is done to assess the immediate effect of the injection. The patient is asked to reproduce his typical discomfort, usually through a series of movements such as bending, twisting, walking, or sitting. Changes in the patient's discomfort provide immediate feedback to both the patient and therapist and helps to identify the etiology of the patient's low back pain. After being monitored for 15-30 minutes, the patient is discharged home.
Selective spinal injections can be placed into the sacroiliac joints, facet joints, epidural space, nerve roots, discs, or congenital bony anomalies. One of the more common spinal injections is the selective nerve root injection. To perform this injection, the patient is placed in a prone position under fluoroscopy. The nerve root exits the spime below its adjacent transverse process and lateral to its adjacent pedicle. After the skin is anesthetized, an 18-gauge needle is placed just inferior to the base of the transverse process, slightly lateral to the pedicle and just deep in the coronal plane to the intertransverse membrane. A 22-gauge spinal needle is then threaded through the 18-gauge needle into the exit zone of the neural foramen. Contrast dye is injected and a radiculogram is reproduced under fluoroscopy. For example, a patient with a right L5 radiculopathy secondary to a disc herniation would undergo a right L5 selective nerve root injection. When contrast is injected over this nerve root, the patient's typical pain is immediately reproduced. Then one to three cc's of 1% Xylocaine, as well as 60-80 mgs of Depo Medrol are injected. Within seconds, the patient's discomfort is diminished as the anesthetic solution is absorbed. An assessment of the injection's efficacy is made within 5 to 15 minutes, as described above. If the patient's pain is largely resolved, then we can be reasonably certain that irritation of the L5 nerve root is the source of the pain.
Derby4 has shown that patients who receive immediate pain relief with selective nerve root injections, often benefit from surgical decompression of the root. Conversely, patients for whom there is no relief of pain after selective nerve root injections have poor surgical outcome. Selective nerve root injections can also be given to patients with a history of previous spinal surgery. For this group of patients, epidural injections are often impossible because of the large amount of epidural fibrosis and bony mass from fusions. However, selective nerve root injections may be very helpful. We have found this technique to be extremely useful in postoperative patients and often is the only technique available to deliver medication to painful nerve roots.
In addition to the diagnostic benefits of these selective spinal injections, we believe these injections often have a substantial therapeutic benefit.5 We are currently reviewing a large group of patients with herniated discs and free fragments in the epidural space who have been treated conservatively with such injections and physical therapy rehabilitation exercises, and have made complete recoveries without surgery. However the utilization of these selective spinal injections should be placed in the continuum of care which includes thorough examinations, appropriate imaging, electrodiagnostics, arid active therapeutic rehabilitation, as well as education. While these injections in and of themselves are not a total medical treatment or cure for any back problem, they can be a very effective form of treatment. It has been proposed by others that maximal therapeutic benefits are obtained through a series of blocks, consisting of three to seven injections performed one week apart. However, there is no current medical literature to support such a proposal. In our experience, selective injections can dramatically reduce the number of injections required: only 50 percent of our patients require a second injection, and only five percent require a third injection.
In conclusion, we feel that selective fluoroscopically-guided spinal injections are the current state of the art for epidural anesthetics and steroids delivery. When combined with other treatment modalities, they may be therapeutic, as well as diagnostic. By using these injection techniques, the need for many types of spinal surgeries can be avoided.
References
1 Mooney V: Where is the pain coming from? Spine 12:754-59, 1987 back
2 White A. Derby R, Wynne G: Epidural injections for the diagnosis and treatment of low-back pain. Spine 5:78-86, 1980. back
3
Poletti S, Johnson D: The use of diagnostic injections in the cervical and lumbar spine. North and South Carolina Orthopedic Society, Charleston, SC. June 1992. back
4 Derby R: Diagnostic block procedures: use in pain localization. Spine: State of the An Reviews. 1:47-64. Sept. 1986. back
5 Stanley D, MeLaren MI, Euinton HA, Getty CJM:
A prospective study of nerve root infiltration in the diagnosis of sciatica; a comparison with radiculography, computed tomography and operative findings.
Spine 15:540-43, 1990. back
* Address correspondence to Dr. Johnson at the Carolina Spine Institute, 247 Calhoun Street, Char1eston, SC 29401. |
