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© 1999 International Anesthesia Research Society
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Abstract |
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Epidural steroids are commonly administered in the treatment of "failed back surgery syndrome." Because patient response is dependent on accurate steroid placement, fluoroscopic guidance has been advocated. However, because of ever-increasing medical expenditures, the cost-benefit of routine fluoroscopy should be critically evaluated. Therefore, 50 patients were enrolled into this institutional review board-approved, prospective, controlled, single-blinded study. At a predetermined intervertebral level, the epidural space was identified using an air loss of resistance technique. Thereafter, an epidural catheter was inserted 2 cm through the epidural needle. To determine the accuracy of the clinical placement, contrast medium was administered through the epidural catheter; antero-posterior and lateral lumbar spine radiographs were then obtained. The number of attempts required to successfully locate the epidural space, the reliability of the air loss of resistance technique in indicating successful epidural penetration in failed back surgery syndrome, the ability of the clinician to accurately predict the intervertebral space at which the epidural injection was performed, and the spread of contrast medium within the epidural space were recorded. A total of 48 epidurograms were performed. The number of attempts to successfully enter the epidural space was 2 ± 1. In 44 cases, the radiological studies confirmed the clinical impression that the epidural space had been successfully identified. In three patients, the epidural catheter was in the paravertebral tissue. One myelogram was recorded. In 25 patients, the epidural catheter did not pass through the predetermined intervertebral space. In 35 cases, the contrast medium did not reach the level of pathology.
Implications: The clinical sign of loss of resistance is a reliable indicator of epidural space penetration in most cases of "failed back surgery syndrome." However, surface anatomy is unreliable and may result in inaccurate steroid placement. Finally, despite accurate placement, the depot-steroid solution will spread to reach the level of pathology in only 26% of cases.
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Introduction |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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Because of their antiinflammatory properties, epidural steroids are often administered in the treatment of low back pain (1–5). To optimize patient response to treatment, the depot-steroid solution is injected through the epidural needle, but it must be placed within the epidural space and as close to the site of pathology as possible (6,7). Although several devices have been developed to assist in the identification of the epidural space (8), manual loss of resistance is the preferred technique (9). To ensure accurate identification of the epidural space, several authors have suggested that needle placement be performed under fluoroscopic guidance (6,10). However, this procedure is time-consuming and costly and requires specialized personnel and radiological facilities.
Low back pain that does not respond to epidural steroid administration is often successfully managed by surgical intervention. However, in some patients, low back and radicular pain are persistent despite adequate surgical decompression (11,12). The resultant "failed back surgery syndrome" is characterized by chronic debilitating pain with consequent psychological and social side effects (13). Similar to that in the nonsurgical patient, epidural steroid administration may reduce local neural tissue inflammation and improve patient comfort. However, because of surgically induced changes in anatomy, apparent loss of resistance may occur at tissue planes other than the epidural space. Therefore, in this setting, the expense associated with fluoroscopy may be justified. However, no prospective studies have been performed to assess the efficacy of fluoroscopy when used as an adjuvant to clinical signs of loss of resistance in failed back surgery syndrome. Therefore, we performed a study designed to assess whether the epidural space can be accurately identified without fluoroscopic guidance in patients suffering from this syndrome. In addition, we evaluated the ability of the clinician to correctly predict the intervertebral space at which the needle and epidural steroids were placed. Finally, spread of contrast medium within the epidural space was recorded.
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Methods |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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After obtaining informed, written consent, 50 patients were enrolled into an institutional review board-approved, prospective, controlled, single-blinded study. All participants were
18 yr of age, had undergone previous spine surgery (laminectomy, discectomy, fusion), and had no obvious radiological cause for the low back or radicular pain. Patients with a history of bleeding disorders and those receiving anticoagulant therapy were excluded from the study. The epidural catheterization and subsequent fluoroscopy were performed by the same professional staff. In all cases, the radiologist interpreting the epidurogram was blinded to the clinical level of pathology and the estimated level of epidural catheterization. The epidural injection was performed in a low care patient holding area. In all cases, lumbar epidural injection was performed. The level of pathology was determined by clinical signs of motor and sensory deficit. The desired intervertebral level was located using the L5-S1 intervertebral space as an anatomical landmark. Furthermore, a line connecting the superior iliac crests located the L4 vertebra. After establishing these anatomical landmarks, adjacent vertebra were palpated and marked. Thus, the anatomy of the lumbar vertebral column was reconstructed, and the intervertebral space closest to the level of pathology was clearly marked.
Before performing the epidural catheterization with the patient in the lateral decubitus position, 1% lidocaine was liberally infiltrated into the skin and subcutaneous tissue in an aseptic fashion. Using an air loss of resistance technique, an epidural catheter was inserted 2 cm through an 18-gauge Tuohy needle (B. Braun, Melsungen, Germany) placed at the interspace closest to the clinical level of pathology. In all cases, the catheter was placed toward the level of pathology.
In the case of accidental dural puncture, the Tuohy needle was removed and the epidural injection was attempted at either one intervertebral space above or below the initial attempt. With the epidural catheter clinically in place, the catheter was firmly taped in position, and the patient was transferred to the radiology suite where fluoroscopy was performed.
Correct placement of the catheter was determined by administering contrast medium (5 mL) through the epidural catheter and by obtaining antero-posterior and lateral lumbar spine radiographs. Spread within the epidural space was determined by placing the patient in both the horizontal and 60° head-up position. Thereafter, both antero-posterior and lateral lumbar spine radiographs were obtained.
On completion of the study, the number of attempts required to successfully locate the epidural space, the correlation between the air loss of resistance technique and fluoroscopic signs of successful epidural space identification in failed back surgery syndrome, the ability of the clinician to accurately predict the intervertebral space at which the epidural injection was performed, and the incidence of spread of contrast medium to the level of pathology were recorded.
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Results |
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The mean age, weight, height, and number of previous surgeries are presented in Table 1. The specific surgical procedure and the relationship among the time since last surgery, number of previous procedures, and number of attempts at epidural placement are presented in Tables 2 and 3, respectively. The nature and number of previous surgeries are presented in Table 4.
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Fifty patients were enrolled into the study (Fig. 1). The mean number of attempts to successfully enter the epidural space was 2 ± 1. In two patients, the epidural space was not located; they were excluded from the study because of repeated accidental dural puncture, and fluoroscopy was not performed. Of the remaining 48 patients, the epidurogram confirmed the clinical impression that the epidural catheter had been successfully placed in the epidural space in 44 (91.7%). Despite positive loss of resistance and easy catheter insertion, radiological studies did not confirm the clinical signs of successful epidural catheterization in four (8.3%). In three patients, the catheter had been placed in paravertebral soft tissue (Fig. 2). In one patient, a myelogram was noted due to subdural catheter placement (Table 4, Patient 21) (Fig. 3). Of the four failures, epidural catheterization was unsuccessful in one patient despite multiple attempts and fluoroscopic guidance (Table 4, Patient 10). In one patient, the second attempt resulted in accidental dural puncture (Table 4, Patient 3). In this patient, fluoroscopy confirmed that the epidural space had been successfully located on the third attempt. In two patients, the epidural catheter was easily placed on the second attempt (Table 4, Patients 21 and 31). In these patients, the clinical signs of successful epidural catheterization were radiologically confirmed.
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The two patients (Table 4, Patients 11 and 33) excluded from the study had undergone either a multilevel laminectomy (L1-2, L2-3, L3-4) or laminectomy (L4-5) and discectomy (L5-S1). The one patient (Table 4, Patient 10) in whom the epidural space was not located despite fluoroscopic guidance had undergone three previous discectomies, as well as posterior fusion for instability of the lumbar spine.
In 22 patients, the radiological studies confirmed the clinical impression of the level at which the catheter had been placed. In 20 patients, the catheter was noted one intervertebral space above or below the level determined by clinical signs. In five patients, fluoroscopy revealed that the catheter had been placed two intervertebral spaces above or below the level determined by clinical signs (Table 5).
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Spread of contrast medium to the level of pathology was noted in 12 patients. In 35 cases, despite placing patients in the 60° head-up position, contrast medium did not reach the level of pathology (Fig. 4).
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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The results of this prospective study suggest that the air loss of resistance technique is a reliable indicator of successful epidural space penetration in most cases of failed back surgery syndrome. This is supported by the fact that, in the 48 radiological studies performed, the clinical signs of successful epidural space catheterization were not confirmed in only four (8.3%) patients. By contrast, fluoroscopy revealed that needle placement at a predetermined intervertebral space is unreliable when based on surface anatomy alone. Of the 47 patients in whom the epidural space was located, fluoroscopy revealed that blinded needle placement at the predetermined intervertebral space was successful in only 22 (47%) patients. In 25 (53%) patients, the Tuohy needle and epidural catheter were placed either one or two intervertebral spaces above or below the desired level (Table 5).
Analysis of the surgical records of the six problematic patients in our study revealed that all these patients had undergone extensive spine surgery. The two patients who were excluded because of repeated dural puncture had undergone either extensive laminectomy or laminectomy and discectomy, respectively (Table 4, Patients 11 and 33). The one patient in whom the epidural space was not located (even under fluoroscopic assistance) had undergone three previous discectomies, as well as lumbar spinal fusion (Table 4, Patient 10). Of the three patients in whom fluoroscopy demonstrated the epidural catheter in the paravertebral tissue, one patient had undergone two previous discectomies (Table 4, Patient 21), and the surgical records revealed accidental dural tear during the surgical procedure in two patients (Table 4, Patients 3 and 31). Of the 44 patients in whom epidural catheter placement was uneventful, 29 patients had undergone one previous surgical procedure, 13 patients had undergone two previous procedures, and 2 patients had undergone previous spine surgery on three occasions (Table 4). The random nature of these results may be due to the effects of the previous spine surgery. In surgical procedures associated with extensive local tissue trauma, the consequent fibrosis and adhesions may complicate epidural needle placement. Furthermore, in cases in which the posterior spinous processes are removed to ensure adequate surgical exposure, counting intervertebral spaces is unreliable and may result in epidural needle placement at the incorrect intervertebral space. Therefore, in procedures associated with extensive tissue trauma or in which the posterior spinous processes are removed, fluoroscopy may ensure more accurate epidural space identification. Thus, the surgical records may be vital when analyzing the cost-benefit of fluoroscopic guidance.
Despite differences in technique, professional training, and patient population, it is interesting to compare our results with those of previous investigators. Although our current study was associated with an 88% success rate without fluoroscopic guidance, White et al. (14) reported that when experienced physicians performed blinded needle placement for lumbar epidural steroid injection, they were successful in only 30% of cases. In addition, El-Khoury et al. (10) reported a 97.5% success rate when caudal epidural steroid administration was routinely preformed under fluoroscopic control. These apparent contradictory results are likely due to the use of fluoroscopy, as well as spine pathology and operator experience. These studies differ from our current investigation in that the study population included patients with acute herniated nucleus pulposus, spinal stenosis, failed back surgery syndrome, and back pain of unknown etiology. Furthermore, in a study designed to assess the influence of professional experience on successful epidural space location, Renfrew et al. (7) demonstrated a direct correlation between the number of previous epidural injections performed and correct blinded needle placement. In this study, physicians who had performed <10 epidural steroid injections were successful in 47.7% of nonfluoroscopically directed attempts. By contrast, blinded needle placement by staff physicians was successful in 61.7% of cases. We attribute our comparatively high success rate to the fact that the epidural injections were always performed by the same highly experienced professional staff. Therefore, we suggest that an epidural steroid injection be performed by experienced personnel in cases of failed back surgery syndrome.
Because optimal patient response to epidural steroid injection requires that the steroid solution be placed at the level of pathology, it is interesting that, although blinded needle placement at the predetermined intervertebral space was successful in 22 of 47 (47%) patients, the contrast medium spread within the epidural space reached the level of pathology in only 12 of 47 (26%) patients. Because fluid spreads to areas of low resistance, surgery-induced adhesions in patients with failed back surgery syndrome may distort normal anatomy and prevent even distribution within the epidural space (15). Furthermore, in most patients, a definite stop in the spread of contrast medium was detected (Fig. 4). Therefore, if the catheter is placed within two levels of the pathology, it is unlikely that diffusion to the level of pathology is dependent on either the catheter position or the volume.
In an era of soaring medical expenditure, the cost-benefit of therapeutic procedures must be critically analyzed. The results of this study suggest that the clinical sign of loss of resistance is a reliable indicator of epidural space penetration in most cases of failed back surgery syndrome. However, despite correct catheter placement, the steroid solution will not reach the level of pathology in most cases. Furthermore, in this population group, anatomical landmarks are unreliable and may result in inaccurate steroid placement.
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References |
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- Saal JS, Franson RC, Dobrow R, et al. High levels of inflammatory phospholipase A2 activity in lumbar disc herniations. Spine 1990;15:674–8.[Web of Science][Medline]
- Takata K, Inoue S, Takahasi K, et al. Swelling of cauda equina in patients who have herniation of a lumbar disc: a possible pathogenesis of sciatica. Am 1988;70:361–8.
- Beliveau P. A comparison between epidural anesthesia with and without corticosteroid in the treatment of sciatica. Rheum Phys Med 1971;11:40–3.
- Dilke TFW, Burry HC, Grahame R. Extradural corticosteroid injection in management of lumbar nerve root compression. BMJ 1973;2:635–7.
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Cuckler JM, Bernini PA, Weisel SW, et al. The use of epidural steroids in the treatment of lumbar radicular pain. Joint Surg Am 1985;67:63–6.
[Abstract/Free Full Text] -
Winnie AP, Hartman JT, Meyers HL, et al. Intradural and extradural corticosteroids for sciatica. Anesth Analg 1972;51:990–1003.
[Free Full Text] - Renfrew DL, Moore TE, Kathol MH, et al. Correct placement of epidural steroid injections: Fluoroscopic guidance and contrast administration. AJNR Am J Neuroradiol 1991;12:1003–7.[Abstract]
- Dawkins CJM. An analysis of complications of extradural and caudal block. Anaesthesia 1969;24:554–63.[Web of Science][Medline]
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El-Khoury G, Ehara S, Weinstein JN, et al. Epidural steroid injection: a procedure ideally performed with fluoroscopic control. Radiology 1988;168:554–7.
[Abstract/Free Full Text] - Law JD, Lehman RAW, Kirsch WM. Reoperation after lumbar intervertebral disc surgery. J Neurosurg 1978;48:259–63.[Web of Science][Medline]
- Wilkinson HA. The role of improper surgery in the etiology of failed back syndrome. In: Wilkinson HA, ed. The failed back syndrome. Philadelphia:JB Lippincott, 1983:15–6.
- North RB, Campbell JN, James CS, et al. Failed back surgery syndrome: 5-year follow-up in 102 patients undergoing repeated operation. Neurosurgery 1991;28:685–90.[Web of Science][Medline]
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[Abstract/Free Full Text]
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