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Departments of Anesthesiology and Intensive Care, Radiology and Spine Surgery, Meir Hospital, Kfar Saba; and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
Address correspondence and reprint requests to Robert Jedeikin, BSc, MB ChB, FFA(SA), Department of Anesthesiology and Intensive Care, Meir Hospital, Kfar Saba 44281, Israel.
| Abstract |
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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.
| Introduction |
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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.
| Methods |
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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.
| Results |
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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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| Discussion |
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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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