Devoted to diagnostic and interventional spine imaging and therapeutics


Influence of Needle Tip Position on the Incidence of Immediate Complications in 2217 Selective Lumbar Nerve Root Blocks 2006

Interventional Spine

Seth T Stalcup, BS, Non ASSR Member
K D Riew, MD, Non ASSR Member
Timothy S Crall, MD, Non ASSR Member
Louis A Gilula, MD, ASSR Member

Scientific Paper


Selective lumbar nerve blocks (SLNBs) are a popular, minimally-invasive treatment and diagnostic tool for lumbar radiculopathy; yet, to our knowledge, the present study is the first to examine the immediate post-procedural complication rates of SLNBs in a large cohort of patients and determine the association between needle-tip position and complication rates. The purposes of the present study were to determine the overall rate of immediate, post-procedural complications in a large cohort of patients who received SLNBs and determine if certain needle-tip positions are less likely to cause complications in order to improve patient safety.

Methods & Materials

Patients who had undergone a SLNB in a single radiology department between April 1, 1997 and May 31, 2002 were retrospectively reviewed after first obtaining Institutional Review Board approval for this study. SLNBs were performed as they would be in the normal course of care, using fluoroscopic guidance and methodology established by a single radiologist overseeing the procedures. Prior to the procedure, information concerning the patient's pre-procedural pain level, including quality and location, was obtained. The Visual Analogue Scale (VAS), where 0 = no pain and 10 = worst possible pain, was used to evaluate pain levels. Patients were then placed in the prone position on a fluoroscopic table with c-arm capabilities to allow visualization of the target lumbar foramen in oblique, lateral, and frontal views. Under fluoroscopic guidance a 22 gauge spinal needle was advanced adjacent or into the intervertebral foramen. Contrast safe to use around neural structures was injected through the spinal needle to confirm that the needle-tip was appropriately placed near the nerve root and to ensure the injectate was not passing intravascularly. Then, a mixture of 1-2cc of anesthetic and 1 cc of a corticosteroid was injected through the spinal needle. If more than one level was to be injected, a separate needle entry-site was used for each injection. After the procedure, the patients were observed for 15-30 minutes and questioned about their pain levels, any new subjective weakness in the legs that developed after the procedure, and any other changes or complications due to the SLNB. Their post-procedural pain VAS levels were then recorded. Patients were not allowed to leave the department until the treating radiologist determined they were stable. The radiologist's record of each visit was examined by an independent observer uninvolved in the procedures to note immediate, post-procedural complications and to determine the overall immediate complication rate for all injections.
In addition, all patients who received only a single injection were compiled into another cohort. Radiographs from the patients who received a single injection during their visit were examined to determine the needle-tip position during the procedure. Both frontal and lateral views were utilized to determine the three-dimensional position of the needle-tip. Horizontal or vertical lines were drawn on the radiographic images, dividing the foramina into quadrants on both the frontal and lateral views. The quadrants were defined as follows: on the frontal view, a vertical line was drawn in the sagittal plane bisecting the pedicle. This line determined if the needle was in the lateral or medial half of the foramen. On the lateral view, a rostral-caudal line was drawn tangent to the curve of the vertebral column at the level of the block bisecting the intervertebral foramen into posterior and anterior halves. A second line was drawn perpendicular to the rostral-caudal line, bisecting the foramen into inferior and superior halves. Each injection was given a position for each of the three planes of section: superior or inferior, anterior or posterior, and medial or lateral. The complication rate of each needle-tip position was determined, and the needle-tip positions from the "Complications" and "No Complications" single injection cohorts were compared to determine if certain needle-tip positions were associated with fewer complications than others.


During the study, 2217 SLNBs were performed during 1777 patient visits. Minor complications were encountered in 98 of these patient visits for an overall complication rate of 5.5%. All complications were transient, and included leg weakness or light-headedness, an increase in pre-procedural pain, or development of new pain that was not concordant with the pre-procedural pain. There were two occurrences of potentially more serious complications: one incident in which the dural sac was punctured but no medication was injected, and another where the medication passed into the subarachnoid space. A review of the charts from both of the patients' subsequent visits to their referring physician's office showed no evidence that either patient suffered lasting harm, nor required any follow-up care resulting from these incidents.
There were 1232 procedures in which the patient received a single injection, and a minor complication was encountered in 62 of these visits. The complication rate approached 5% for all needle-tip positions, which is not statistically different from the overall complication rate. However, there was an increased likelihood of complications in patients undergoing a multiple injection procedure versus those who had only one injection (4.81% complication rate for single injections, 7.88% complication rate for multiple injections, p=0.025).


As with any invasive procedure, SLNBs carry an inherent risk of complications, but our results suggest that SLNBs performed with fluoroscopic guidance by experienced physicians have an acceptably low overall incidence of immediate post-procedural complications. Prior to this study the complication rates of SLNBs have only been examined in small series, mentioned in case reports, or included as part of a large cohort in which only major complications requiring an ER visit or hospitalization were reported. Our study is the first to examine immediate post-procedural complications of SLNBs and to correlate the needle-tip position with complication incidence. All complications encountered in our study were transient and quickly resolved. Based on our data, there was no statistically significant difference between the average complication rates among various needle-tip positions. In other words, there is no optimum needle-tip position within or adjacent to the neural foramen to avoid complications, so physicians need not feel compelled to place the needle in any certain quadrant of the neural foramen.


There is no financial involvement in this research from any commercial entity. This work has not been presented at a prior meeting and is not published to date.

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