Injection Procedures
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In following up my discussion of the use of steroid blocks to alleviate back pain cased by traumatic injuries, I think many will want to know specifics about the procedure,
Injection Details:The interval between the injections varies with the steroid preparations used. Since injected methylprednisolone was reported to remain in situ for approximately 2 weeks, the clinician should expect to wait 2 weeks after the injection to assess the patient's response and to administer a repeat injection. However, this 2-week interval may be shortened if using a different steroid (short-acting steroid). Of course, clinical judgment often guides the most appropriate timing in a given patient.
Clinicians and patients often must consider the number of ESIs that should be performed. Studies have demonstrated that patients who did not respond to an initial injection did still show improvement after 1 or 2 more epidural steroid injections. In general, up to 3-4 epidural injections may be performed if clinically indicated. Some clinicians schedule a series of 3 ESIs and proceed with these regardless of the clinical response to the first 1 or 2 injections. However, there are no medical outcome studies to clearly support such a regiment.
The volume of the injection is dictated mainly by the approach used. In cervical and thoracic epidural injections, a total of 3-5 mL may be used for ESIs using the interlaminar approach. However, in transforaminal ESIs, clinicians generally use a total volume of only about 1.5-2 mL. The volume used for lumbar ESIs is slightly greater, generally using 6-10 mL for interlaminar ESIs, up to 20 mL for caudal ESIs, and 3-4 mL for transforaminal ESIs. For interlaminar ESIs, 13 typical corticosteroid doses are 12-18 mg for Celestone and 80-120 mg for Methylprednisolone. Half of these steroid doses are generally used when performing transforaminal ESIs.
Injection Technique:Cervical, thoracic, and lumbar epidural injections can be approached through translaminar and transforaminal injections. Lumbar epidural injection can be performed using 3 approaches. Translaminar epidural injection refers to injection into the interlaminar space of the spine. Hence, many spine specialists refer to translaminar injection as interlaminar injection. The interlaminar epidural injection can be performed through paramedian or midline approaches. The epidural needle penetrates skin, subcutaneous tissue, paraspinal muscles (paramedian approach) or interspinous ligament (midline approach), and ligamentum flavum. Transforaminal approach is performed by placing the needle in the neuroforamen ventral to the nerve root. The needle is directed in an oblique approach until the tip of the needle touches the posterior lateral portion of the vertebral body, located superior to the intervertebral foramen just under the pedicle. Caudal lumbar epidural injections may be performed by inserting a needle through the sacral hiatus into epidural space at the sacral canal.
As mentioned previously, reports suggest that injection without fluoroscopic guidance (ie, blind injection) result in 30-40% of needle misplacement, including needle tip placement outside the epidural space (eg, intravascular injection) and not at presumed level of pathological process. Therefore, although it is not a standard, it is recommended that ESIs be performed under fluoroscopic guidance and with radiographic contrast documenting appropriate placement in order to improve safety, accuracy, and potential efficacy of ESIs.
