Influence of Needle Tip Position on Injectate Spread in 406 Interlaminar Lumbar Epidural Steroid Injections1

Contrast flow in CT-guided lumbar interlaminar epidural steroid injections: does needle position effect the laterality of contrast flow?

PURPOSE

To evaluate the effect of needle position on the laterality of contrast flow in CT-guided lumbar interlaminar epidural steroid injections.

MATERIALS AND METHODS

A retrospective review of consecutive CT-guided interlaminar lumbar epidural steroid injections was performed. The terminal needle tip position (midline or lateral) and the laterality of epidural contrast were evaluated by two readers. Contrast flow pattern was classified as ipsilateral to needle trajectory, bilateral, or contralateral. Bilateral flow was further divided into asymmetric, symmetrical, or asymmetric to the contralateral side. Inter-reader agreement was calculated with the kappa statistic. The relationship of needle position to contrast laterality was calculated with the chi statistic. Pain scores were compared for bilateral and unilateral flows with a two-tailed T test for independent means.

RESULTS

A total of 250 injections were included in 204 patients, with an age range of 24 to 93 years. The most commonly injected level (145/250) was L4-L5. Agreement between the two readers was almost perfect and substantial (kappa 0.751-0.880). The majority of injections (154/250) demonstrated contrast flow ipsilateral to the needle trajectory, 90/250 demonstrated bilateral flow, and 6/250 had contralateral flow. Of the 90 cases with bilateral flow, 80% were performed with a midline terminal needle position (p < 0.001). There was no difference in immediate post-procedure pain scores between patients with ipsilateral or bilateral contrast flow.

CONCLUSION

For interlaminar epidural steroid injections, a midline terminal needle tip position has a greater probability of producing bilateral contrast flow compared to a lateral terminal needle tip position.

Evaluation of Contrast Flow Patterns with Cervical Interlaminar Epidural Injection: Comparison of Midline and Paramedian Approaches

Background and objectives: The purpose of this study was to compare and to analyze contrast spread patterns between the paramedian and midline approaches to cervical interlaminar epidural injection (CIEI). Materials and Methods: We retrospectively enrolled 84 CIEI cases that had been performed for unilateral cervical spinal pain from April 2019 to April 2020. After 3 mL of contrast had been injected into the epidural space, fluoroscopic images were obtained. The CIEI was divided into a midline (Group M, n = 42) and a paramedian (Group P, n = 42) approach by anteroposterior imaging. The P Group was classified into a more medial (Group Pm, n = 26) and a more lateral (Group Pl, n = 16) group. Using ImageJ on an anteroposterior image, we assessed the grayscale brightness ratio of the ipsilateral or contralateral side of the vertebral body as well as the intervertebral disc space one level just above the needle location. We identified the dispersion of contrast into the ventral epidural space. Results: The grayscale brightness ratio was significantly higher in Group P than in Group M (p < 0.001). The incidence of ventral epidural spread in Group M was 57.1% versus 88.1% in Group P, which was significantly different (p = 0.001). Conclusions: The fluoroscopic CIEI finding in the paramedian approach predominantly showed an excellent delivery of the injectate to the ipsilateral side in comparison to the contralateral side. This showed a greater advantage in delivery toward ventral epidural space as compared to the midline approach.

Lumbar epidural steroid injections for herniation and stenosis: incidence and risk factors of subsequent surgery

BACKGROUND CONTEXT

Lumbosacral epidural steroid injections (ESIs) have increased dramatically despite a narrowing of the clinical indications for use. One potential indication is to avoid or delay surgery, yet little information exists regarding surgery rates after ESI.

PURPOSE

The purpose of this research was to determine the proportion of patients having surgery after lumbar ESI for disc herniation or stenosis and to identify the timing and factors associated with this progression.

STUDY DESIGN/SETTING

This study was a retrospective review of nationally representative administrative claims data from the Truven Health MarketScan databases from 2007 to 2014.

PATIENT SAMPLE

The study cohort was comprised of 179,025 patients (54±15 years, 48% women) having lumbar ESIs for diagnoses of stenosis and/or herniation.

OUTCOME MEASURES

The primary outcome measure was the time from ESI to surgery.

METHODS

Inclusion criteria were ESI for stenosis and/or herniation, age ≥18 years, and health plan enrollment for 1 year before ESI to screen for exclusions. Patients were followed longitudinally until they progressed to surgery or had a lapse in enrollment, at which time they were censored. Rates of surgery were assessed with the Kaplan-Meier survival curves. Demographic and treatment factors associated with surgery were assessed with multivariable Cox proportional hazard models. No external funding was procured for this research and the authors' conflicts of interest are not pertinent to the present work.

RESULTS

Within 6 months, 12.5% of ESI patients underwent lumbar surgery. By 1 year, 16.9% had surgery, and by 5 years, 26.1% had surgery. Patients with herniation had surgery at rates of up to five-fold to seven-fold higher, with the highest rates of surgery in younger patients and those with both herniation and stenosis. Other concomitant spine diagnoses, male sex, previous tobacco use, and residence a rural areas or regions other than the Northeastern United States were associated with higher surgery rates. Medical comorbidities (previous treatment for drug use, congestive heart failure, obesity, chronic obstructive pulmonary disease, hypercholesterolemia, and other cardiac complications) were associated with lower surgery rates.

CONCLUSIONS

In the long term, more than one out of every four patients undergoing ESI for lumbar herniation or stenosis subsequently had surgery, and nearly one of six had surgery within the first year. After adjusting for other patient demographics and comorbidities, patients with herniation were more likely have surgery than those with stenosis. The improved understanding of the progression from lumbar ESI to surgery will help to better inform discussions regarding the value of ESI and aid in the shared decision-making process.

The role of epidural contrast distribution in predicting the effectiveness of steroid and local anesthetic injection in patients with lumbar spinal stenosis

STUDY DESIGN

A prospective observational comparative study.

BACKGROUND

Because epidural corticosteroids are more effective for pain relief when delivered close to the site of pathology, lumbar spinal stenosis with multilevel stenotic areas can be treated more effectively when medications cover all of the stenotic areas. Distribution of medications to the pathologic sites is considered an important factor in the effectiveness of inter-laminar epidural injection.

OBJECTIVE

To determine whether spread of a lidocaine and triamcinolone mixture over the stenotic areas improves clinical symptom of spinal stenosis more effectively.

METHODS

Twenty-four patients with lumbar spinal stenosis were enrolled in this study. A lumbar inter-laminar epidural injection under fluoroscopic guidance was administered to each patient. A numeric rating scale (NRS), claudication distance, the Romberg test, and the Oswestry Disability Index (ODI) were checked pre-injection and at 2, 6, and 12 weeks after the epidural injection. Vertebrae that showed more than moderate stenosis were considered stenosis levels. Inter-laminar epidural injection was performed with radiopaque contrast and lidocaine mixed with triamcinolone acetate. When the contrast covered all of the stenosis levels, this was considered a sufficient distribution (SD) and when the contrast did not cover all stenosis levels, this was considered an insufficient distribution (ID).

RESULTS

At 2 weeks, percentages of NRS improvement were 71.4 (IQR, 20.2) in SD group and 50.0 (IQR, 31.4) in ID group (P= 0.02), changes in Romberg test time were 0.0 (IQR, 35.0) in SD group and -3.0 (IQR, 12.0) in ID group (P= 0.02), decreases in ODI were 9.6 (IQR, 11.2) in SD group and 0.0 (IQR, 7.8) in ID group (P= 0.02). However, these parameters were not significantly different at 6 weeks and 12 weeks. Claudication distance showed no significant group difference.

CONCLUSION

Coverage of the stenotic area by the lidocaine, triamcinolone, and contrast dye mixture during inter-laminar epidural injection was an important predictor of acute pain reduction.

Spinal Injections for Pain Management

Image-guided spinal injection is commonly performed in symptomatic patients to decrease pain severity, confirm the pain generator, and delay or avoid surgery. This article focuses on the radiologist as spine interventionist and addresses the following four topics relevant to the radiologist who performs corticosteroid injections for pain management: (a) the rationale behind corticosteroid injection, (b) the interaction with patients, (c) the role of imaging in procedural selection and planning, and (d) the pearls and pitfalls of fluoroscopically guided injections. Factors that contribute to the success of a pain management service include communication skills and risk mitigation. A critical factor is the correlation of clinical symptoms with magnetic resonance (MR) imaging findings. Radiologists can leverage their training in MR image interpretation to distinguish active pain generators in the spine from incidental abnormalities. Knowledge of fluoroscopic anatomy and patterns of contrast material flow guide the planning and execution of safe and effective needle placement. ^© RSNA, 2016 Online supplemental material is available for this article.

Safety of Epidural Corticosteroid Injections

BACKGROUND AND OBJECTIVE

Epidural corticosteroid injections (ESIs) have been used for several decades and now represent the most common intervention performed for the management of back pain with a radicular component. However, several reports have presented devastating complications and adverse effects, which fuelled concerns over the risk versus clinical effectiveness. The authors offer a comprehensive review of the available literature and analyse the data derived from studies and case reports.

METHODS

Studies were identified by searching PubMed MEDLINE, Ovid MEDLINE, EMBASE, Scopus, Google Scholar and the Cochrane Library to retrieve all available relevant articles. Publications from the last 20 years (September 1994 to September 2014) were considered for further analysis. Studies selected were English-language original articles publishing results on complications related to the technique used for cervical and lumbar ESIs. The studies had to specify the approach used for injection. All studies that did not fulfil these eligibility criteria were excluded from further analysis.

RESULTS

Overall, the available literature supports the view that serious complications following injections of corticosteroid suspensions into the cervical and lumbar epidural space are uncommon, but if they occur they can be devastating.

CONCLUSIONS

The true incidence of such complications remains unclear. Direct vascular injury and/or administration of injectates intra-arterially represent a major concern and could account for the vast majority of the adverse events reported. Accurate placement of the needle, use of a non-particulate corticosteroid, live fluoroscopy, digital subtraction angiography, and familiarisation of the operator with contrast patterns on fluoroscopy should minimise these risks. The available literature has several limitations including incomplete documentation, unreported data and inherent bias. Large registries and well-structured observational studies are needed to determine the true incidence of adverse events and address the safety concerns.

Fluoroscopically guided lumbar facet joint injection using an interlaminar approach and loss of resistance technique

PURPOSE

To describe a new technique for performing fluoroscopically guided lumbar facet joint injections using an interlaminar approach and loss-of-resistance technique and to report the initial success rate of this technique in a small series of patients.

MATERIALS AND METHODS

The institutional radiology database was retrospectively reviewed to identify patients who underwent fluoroscopically guided lumbar facet joint injections. Between 1 May 2014 and 31 October 2015, one radiologist attempted fluoroscopically guided lumbar facet joint injections using an interlaminar approach and loss-of-resistance technique in ten severely osteoarthritic facet joints (4 patients). Patient demographics, facet joint side and level, and whether or not an intra-articular facet joint injection was achieved were recorded.

RESULTS

Intra-articular injection was achieved using the interlaminar approach and loss-of-resistance technique in five facet joints.

CONCLUSION

Fluoroscopically guided lumbar facet joint injection using an interlaminar approach and loss-of-resistance technique is an alternative approach to a direct posterior facet joint injection and may be particularly useful for severely osteoarthritic facet joints, where bulky osteophytes and/or extreme curvature of the joints in the transverse plane threaten to preclude direct posterior access to the joints.

Access routes and reported decision criteria for lumbar epidural drug injections: a systematic literature review

PURPOSE

To review lumbar epidural drug injection routes in relation to current practice and the reported criteria used for selecting a given approach.

MATERIAL AND METHODS

This was a HIPPA-compliant study. Employing a systematic search strategy, the MEDLINE and EMBASE databank as well as the Cochrane Library were searched for studies on epidural drug injections. The following data were noted: access route, level of injection, use of image guidance, and types and doses of injected drugs. Justifications for the use of a particular route were also noted. Data were presented using descriptive statistics.

RESULTS

A total of 1,211 scientific studies were identified, of which 91 were finally included (7.5%). The interlaminar access route was used in 44 of 91 studies (48.4%), the transforaminal in 37 of 91 studies (40.7%), and the caudal pathway in 26 of 91 studies (28.6%). The caudal pathway was favored in the older studies whereas the transforaminal route was favored in recent studies. Decision criteria related to correct needle placement, concentration of injected drug at lesion site, technical complexity, costs, and potential complications. Injection was usually performed on the level of the lesion using local anesthetics (71 of 91 studies, 78.0%), steroids (all studies) and image guidance (71 of 91 studies, 78%).

CONCLUSIONS

The most commonly used access routes for epidural drug injection are the interlaminar and transforaminal pathways at the level of the pathology. Transforaminal routes are being performed with increasing frequency in recent years.

Some epidurographic explanations for incomplete epidural analgesia coverage in the absence of a catheter

STUDY OBJECTIVE

To determine the impact of the plica mediana dorsalis (PMD) on injected contrast media spread in the epidural space.

DESIGN

Prospective interventional study.

SETTING

Academic medical center.

PATIENTS

30 chronic pain patients ranging in age from 37 to 71 years, undergoing epidural steroid injection.

INTERVENTIONS AND MEASUREMENTS

Epidurograms were evaluated for the 1) presence or absence of a PMD and 2) bilateral differential density and the extent of contrast spread on either side of the midline, horizontally and vertically.

RESULTS

The PMD (defined as midline radiolucency in epidurograms) was observed in (80%) 24/30 patients based on the epidurograms that were evaluated. Denser contrast spread on one side was found in (79%) 19/24 patients who had the PMD and in (33%) 2/6 patients who did not have the PMD (P = 0.03). Horizontal and vertical asymmetrical spread of the contrast was observed in (67%) 16 of 24 patients with the PMD and in (50%) 3 of 6 of patients without the PMD in each direction independently.

CONCLUSION

The difference in density of contrast spread on either side of the midline carries important clinical implications in understanding the pathogenesis of inadequate epidural analgesia and/or unilateral excessive motor weakness or numbness.

Immediate pain response to interlaminar lumbar epidural steroid administration: response characteristics and effects of anesthetic concentration

BACKGROUND AND PURPOSE

Interlaminar LESIs are commonly used to treat LBP or radiculopathy. Most studies focus on the long-term outcomes of LESI. The purpose of this study is to evaluate the immediate effects of fluoroscopically guided LESI on LBP/radiculopathy including low- or high-strength anesthetic response.

MATERIALS AND METHODS

The procedure notes, post-procedure records, and imaging records dedicated spine nurse assessments, and imaging records were retrospectively evaluated in 392 fluoroscopically guided LESIs performed in 276 patients (nonrandomized, nonblinded; 131 males, 145 females; average age, 56 years) with LBP/radiculopathy using either low- or high-strength anesthetic (80 mg of methylprednisilone mixed with bupivacaine [0.25% or 0.5%]). Post-procedure documentation of the patient's pre- and postprocedure VAS pain-scale level were tabulated.

RESULTS

Single LESI was performed in 199 patients, with multiple LESIs in 77 (193 injections). Low-strength bupivacaine (0.25%) was used in 237 injections, with high-strength (0.5%) in 155. Complete to near-complete immediate pain relief (<20% residual pain) was reported after 197 of 392 (50.3%) injections. No pain relief was reported after 60 (15.4%) injections (>80% residual), with partial relief in the remainder. No statistical difference was noted between low- and high-anesthetic strength or between single- and multiple-injection patients. In multiple-LESI patients, consistent pain relief response was noted in 39 of 77 (50.6%) patients, with improving LESI response in 20.8%, deteriorating LESI response in 19.5%, and variable response in 9.1%.

CONCLUSIONS

An immediate pain-extinction response is identified after LESI, which appears independent of anesthetic strength. This observation may relate to pain origin and/or pain nociceptor afferent pathway in an individual patient and potentially relate to treatment response.

An evaluation of contrast medium spread on caudal epidurography with the needle positioned toward the affected side in patients with unilateral lumbosacral radiculopathy

OBJECTIVE

We used caudal epidurography to compare the spread of contrast medium when the needle was inserted toward the affected side in patients with unilateral radiculopathy undergoing caudal steroid injection.

MATERIALS AND METHODS

We enrolled 24 patients with unilateral radiculopathy. A block needle was positioned toward the affected side in the sacral epidural space. After 5 mL of iodinated contrast medium was injected, a standardized anteroposterior view was imaged. Using Adobe Photoshop software, contrast medium spread was assessed by counting pixels within the areas spread on the affected side and on the opposite side, and the pixel counts of the two sides were compared. Spinal nerve root filling was also assessed.

RESULTS

The pixel count within the area of contrast medium spread on the side with the needle was significantly greater than that of the opposite side (mean [SD] 41,368.6 [13,143.1] vs 15,165.3 (10,698.1), P < 0.001]. However, 13.6% of the study patients had greater spread on the opposite side. The rates of L5 and S1 nerve root filling in the affected side were 18.2% and 36.4% respectively.

CONCLUSIONS

When a needle was intentionally inserted toward the side with radiculopathy, the spread of contrast medium and number of delineated roots tended to be greater on the side with the needle, compared with those on the opposite side. However, the pattern of contrast medium spread in the sacral epidural space varied and some patients even had greater spread on the opposite side.

Injectate volumes needed to reach specific landmarks in s1 transforaminal epidural injections

OBJECTIVES

  We identify the contrast volumes needed to reach specific landmarks during S1 transforaminal epidural injections (S1-TFEIs).

DESIGN

  Prospective, nonrandomized, observational human study. Setting.  Academic/private pain management practice. Subjects.  Forty-two patients undergoing S1-TFEIs were investigated. Thirty-seven patients were included in this study. Interventions.  S1-TFEIs were performed using contrast-enhanced fluoroscopic visualization.

MAIN OUTCOME MEASUREMENTS

  After confirming appropriate spinal needle position, up to 5 mL of nonionic contrast was slowly injected. Under biplanar fluoroscopic guidance, contrast volumes were recorded as flow reached specific anatomic landmarks: the ipsilateral S1 pedicle, the superior aspect of the L5-S1 disc space, and across the midline of the spinous process.

RESULTS

  After injecting 2 mL of contrast, 100% of S1-TFEIs spread to the medial aspect of the ipsilateral superior pedicle of S1. After injecting 3.0 mL of contrast, 92% of S1-TFEIs spread to the superior aspect of the L5-S1 intervertebral disc. After injecting 4 mL of contrast, 27% of S1-TFEIs spread beyond the midline of the spinous process, but by only a few millimeters.

CONCLUSIONS

  This study demonstrates injectate volumes needed to reach specific anatomic landmarks in S1-TFEIs. A volume of 3.0 mL of contrast reaches the superior aspect of the L5-S1 intervertebral disc 92% of the time.

Dispersal pattern of injectate after lumbar interlaminar epidural spinal injection evaluated with computerized tomography

Study Design Retrospective analysis of lumbar computed tomographic epidurograms. Objective To evaluate the dispersal pattern of injectate after interlaminar lumbar epidural steroid injections. Summary Prior studies have evaluated the dispersal patterns of injectate after lumbar epidural steroid injections using fluoroscopy with varying results. To date, there have been no studies evaluating the dispersal pattern utilizing computerized tomography. Methods Ten epidurograms were analyzed after lumbar interlaminar epidural steroid injection. The epidurograms were examined, evaluating the dispersal pattern in longitudinal flow as well as circumferential flow. In addition, pain values were assessed with the visual analogue scale. Results Mean diffusion in the rostral direction was 9.8 cm (standard deviation 4.0 cm, range 4.0 to 15.0 cm). Mean diffusion in the caudal direction was 5.4 cm (standard deviation 1.4 cm, range 3.0 to 8.0 cm). Both rostral and caudal flow had a p value < 0.001. The circumferential flow was 360 degrees in 9 of 10 cases. In addition, there was significant (p = 0.006) reduction in pain. Conclusion Interlaminar lumbar epidural steroid injections are an effective treatment modality for various spine-related conditions. The injectate diffuses throughout the epidural space with nearly uniform circumferential flow as well as significant rostral and caudal flow.

Incidence of inadvertent intra-articular lumbar facet joint injection during fluoroscopically guided interlaminar epidural steroid injection

OBJECTIVE

To determine the incidence of inadvertent lumbar facet joint injection during an interlaminar epidural steroid injection (ESI).

MATERIALS AND METHODS

A total of 686 interlaminar lumbar ESIs were performed from January 1, 2009 to December 31, 2009. Archived images from these cases were retrospectively reviewed on the PACS. Positive cases of inadvertent lumbar facet joint injection were identified by the characteristic sigmoid-shaped contrast pattern projecting over the posterior elements on the lateral view and/or ovoid contrast projecting over the facet joints on the anteroposterior (AP) view.

RESULTS

Eight positive events were identified (1.2%). There was no statistically significant gender or lumbar level predilection. In 3/8 of the positive cases (37.5%), the inadvertent facet joint injection was recognized by the operator. The needle was repositioned as a result, and contrast within the posterior epidural space was documented by the end of the procedure. In 5/8 of the positive cases (62.5%), the patients reported an immediate decrease in the presenting pain.

CONCLUSIONS

The incidence of inadvertent lumbar facet joint injection during an interlaminar epidural steroid injection is low. Recognizing the imaging features of this event permits the operator to redirect the needle tip into the epidural space and/or identify the facet joint(s) as a source of the patient's presenting pain.

Inadvertent intra-articular lumbar facet joint injection during fluoroscopically guided interlaminar epidural steroid injection

OBJECTIVE

Inadvertent lumbar facet joint injection during an interlaminar epidural steroid injection (ESI) is rare when using the loss-of-resistance technique. The pattern of contrast material on the lateral view can mimic that of a successful ESI. The purpose of this study is to illustrate the imaging features of this event.

MATERIALS AND METHODS

From 2001 to 2009, 6,631 interlaminar lumbar ESIs were performed. Cases in which facet joint injection was recognized by the radiologist were identified by a text search of the report for the term "facet" and corroborated by review of the case images and the patients' medical records.

RESULTS

Forty-two positive events were identified. Imaging features are characteristic and include sigmoid-shaped area of contrast material projecting over the posterior elements on the lateral view and an ovoid area of contrast material projecting over the facet joints on the anteroposterior (AP) view. Thirty-one out of 42 events were recognized by the operator during the procedure. In 17 cases, the final images documented the appropriate location of the needle tip within the epidural space. In 9 cases, simultaneous epidural and facet joint injection occurred. In 16 cases, epidural contrast material was not documented.

CONCLUSION

Lumbar facet joint injection has a characteristic appearance and can be distinguished from epidural injection. However, since this event can simulate the appearance of a successful ESI, it may be unrecognized during the procedure. Therefore, the true incidence is likely higher than that suggested by this study. Recognizing the imaging features of this event permits the operator to further manipulate the needle tip and increase the success rate of ESIs.

Injectate volumes needed to reach specific landmarks in lumbar transforaminal epidural injections

OBJECTIVES

To identify the volumes of contrast material needed to reach specific landmarks during lumbar transforaminal epidural injections (L-TFEIs).

DESIGN

Prospective, nonrandomized, observational human study.

SETTING

Academic/private pain management practice.

PATIENTS

Sixty-nine patients undergoing L-TFEIs were investigated. Sixty patients were included in this study.

INTERVENTIONS

L-TFEIs were performed with the use of contrast-enhanced fluoroscopic visualization.

MAIN OUTCOME MEASUREMENTS

After the appropriate spinal needle position was confirmed, up to 5.0 mL of nonionic contrast material was slowly injected. Under biplanar fluoroscopic guidance, contrast volumes were recorded as flow reached specific anatomic landmarks: ipsilateral neural foramen, ipsilateral disks superior and inferior to the injected level, and across the midline of the spinous process.

RESULTS

After 1.1 mL of contrast was injected, 100% of L-TFEIs spread to the medial aspect of the superior pedicle (PED) of the corresponding level of injection. After 2.8 mL of contrast was injected, 95% of L-TFEIs spread to the superior aspect of the superior intervertebral disk (IVD) of the corresponding level of injection. After 3.6 mL of contrast was injected, 95% of L-TFEIs spread to the inferior aspect of the inferior IVD of the corresponding level of injection. After 3 mL of contrast was injected, 88% of L-TFEIs spread to cover both the superior and inferior IVDs of the corresponding level of injection. After 4 mL of contrast was injected, 93% of L-TFEIs spread to cover both the superior and inferior IVDs of the corresponding injection. After 4 ml of contrast was injected, 55% of L-TFEIs spread beyond the midline of the spinous process, but barely.

CONCLUSION

This study demonstrates injectate volumes needed to reach specific anatomic landmarks in L-TFEIs. A volume of 4.0 mL of injectate reaches both the superior aspect of the superior IVD and the inferior aspect of the inferior IVD 93% of the time.

Lumbar epidural steroid injections: indications, contraindications, risks, and benefits

The clinical use of lumbar epidural steroid injections has increased dramatically. Although there are certainly beneficial effects to using epidural steroid injections in a treatment regimen for lumbar radicular pain, there is a lack of well designed, placebo-controlled studies to define conclusively specific indications and techniques for different spinal diagnoses. This article reviews the pathophysiology of lumbar radiculopathy and the use of epidural steroid injections as one treatment option, as well as describes their risks and benefits. Based on current literature, we offer an evidence-based perspective regarding rational use of lumbar epidural steroid injections for certain indications and treatment goals.

A prospective, observational study of the relationship between body mass index and depth of the epidural space during lumbar transforaminal epidural steroid injection

BACKGROUND AND OBJECTIVES

Previous studies have concluded that transforaminal epidural steroid injections (ESIs) are more effective than interlaminar injections in the treatment of radiculopathies due to lumbar intervertebral disk herniation. There are no published studies examining the depth of epidural space using a transforaminal approach. We investigated the relationship between body mass index (BMI) and the depth of the epidural space during lumbar transforaminal ESIs.

METHODS

Eighty-six consecutive patients undergoing lumbar transforaminal ESI at the L3-L4, L4-L5, and L5-S1 levels were studied. Using standard protocol, the foraminal epidural space was attained using fluoroscopic guidance. The measured distance from needle tip to skin was recorded (depth to foraminal epidural space). The differences in the needle depth and BMI were analyzed using regression analysis.

RESULTS

Needle depth was positively associated with BMI (regression coefficient [RC], 1.13; P < 0.001). The median depths (in centimeters) to the epidural space were 6.3, 7.5, 8.4, 10.0, 10.4, and 12.2 for underweight, normal, preobese, obese I, obese II, and obese III classifications, respectively. Sex (RC, 1.3; P = 0.02) and race (RC, 0.8; P = 0.04) were also significantly associated with needle depth; however, neither factor remained significant when BMI was accounted as a covariate in the regression model. Age, intervertebral level treated, and oblique angle had no predictive value on foraminal depth (P > 0.2).

CONCLUSION

There is a positive association between BMI and transforaminal epidural depth, but not with age, sex, race, oblique angle, or intervertebral level.