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Background: During lumbar epidural injection (LEI) using a midline approach, we might encounter failure of identifying the epidural space owing to an equivocal or absent loss of resistance (LOR) sensation. The reason for such absence of LOR sensation has been suggested as paucity of midline ligamentum flavum, paravertebral muscle, and cyst in the interspinous ligament of the lumbar spine. Despite its low specificity, LOR is the most commonly used method to identify the epidural space. Objectives: The purpose of this study was to analyze lumbar epidural pressure decrease patterns and identify factors contributing to this pressure decrease. Study Design: Prospective randomized trial. Setting: An interventional pain management practice in South Korea. Methods: This prospective study included 104 patients receiving LEI due to lumbar radiculopathy. A midline or paramedian approach of LEI was determined with randomization. Among various factors, gender, age, body mass index (BMI), and diagnosis were analyzed using a subgroup that included 60 cases of only a paramedian approach. Results: Grades I, II (abrupt decrease), and III (gradual decrease) were found as patterns of epidural pressure decrease. Abrupt pressure decrease was more frequently observed in the paramedian group (P < 0.001). Age, gender, BMI, and diagnosis did not show any significant difference in frequencies between abrupt and gradual pressure decrease. Limitations: We could not match LOR sensation with epidural pressure decrease shown in the monitor. Conclusions: This study demonstrates that abrupt pressure decrease occurs more frequently with the paramedian approach. However, age, gender, BMI, or diagnosis did not affect the incidence of epidural pressure decrease. Key words: Epidural, paramedian, midline, pressure decrease

Background: Interlaminar epidural steroid injection (ESI) is a well-established intervention to improve radicular leg pain. However, few studies have demonstrated the prognostic factors for interlaminar ESI. Objective: To investigate the clinical effectiveness and prognostic indicators of parasagittal interlaminar ESI during a 2-week follow-up. Study Design: Prospective evaluation. Setting: An interventional pain management practice in South Korea. Methods: After Institutional Review Board approval, parasagittal interlaminar ESI under fluoroscopic guidance was performed in 55 patients with central spinal stenosis. The numerical rating scale (NRS) and the Oswestry Disability Index (ODI) (%) were used to evaluate clinical efficacy and prognostic indicators. To determine the prognostic indicators, treatment outcomes were classified as successful (decreased NRS ≥ 50%, decreased ODI ≥ 40%) and unsuccessful (decreased NRS < 50%, decreased ODI < 40%) results. Results: Parasagittal interlaminar ESI significantly improved the NRS and ODI (%) scores after 2 weeks compared to those measured pretreatment. Paresthesia provocation (P = 0.006) was a significant prognostic factor on the NRS, whereas the Beck Depression Inventory (BDI) score (P = 0.007), paresthesia provocation (P = 0.035), and epidurography finding (P = 0.038) were significant on the ODI (%) score between patients with successful and unsuccessful outcomes. Limitations: We included the method of parasagittal interlaminar ESI only, therefore, direct comparison with other techniques was not available. Conclusion: Parasagittal interlaminar ESI significantly improved the NRS and ODI (%) scores. Paresthesia provocation was a prognostic indicator on the NRS and ODI (%) scores, and BDI scores and epidurography findings were prognostic indicators for the ODI (%) score. Key words: Parasagittal interlaminar epidural steroid injection, spinal stenosis, radicular leg pain, prognostic indicator, paresthesia provocation, epidurography, Beck Depression Inventory

Background: Transforaminal epidural steroid injection (TFESI) is a commonly used interventional pain management procedures to treat radicular leg pain. Although most reported complications of TFESI are minor, serious morbidity has also been demonstrated including spinal cord infarction, paraplegia, and quadriparesis. Suggested mechanisms include direct vascular injury or intravascular injection of particulate steroid. Objective: We compared 2 different needle types, Whitacre and Quincke type needles, with regard to intravascular injection rate with total procedure time and the amount of radiation during lumbar TFESI. Study Design: Prospective, randomized trial. Setting: An interventional pain management practice in South Korea. Methods: After Institutional Review Board approval, 149 patients undergoing lumbar TFESI for radicular leg pain were randomly assigned to one of 2 needle groups (Whitacre needle or Quincke type needle). After final confirmation of intravascular injection with digital subtraction angiography, total procedure time and amount of radiation exposure during TFESI were measured. Results: The overall incidence of intravascular injection was 10.4% (28/269). We analyzed the overall incidence of intravascular injection according to the 2 different needle types. The incidence of intravascular injection of the Whitacre needle was 5.4% (8/146), whereas the incidence of intravascular injection of the Quincke needle was 16.2% (20/123). Total procedure time and amount of radiation required to complete the TFESI in the Whitacre and Quincke needle groups was 168.4 ± 57.9 (seconds) and 33.4 ± 15.9 (cGy/cm2 ), 131.9 ± 46.0 (seconds) and 33.2 ± 15.8 (cGy/cm2 ), respectively. Limitations: The physician who performed the TFESI was not blinded to the type of needle for detecting intravascular injection. This study was focused on lumbar TFESI, however, most TFESIs are performed at the L4-5 or L5-S1 level. Conclusion: The Whitacre needle had the benefit of reducing the incidence of intravascular injection with minimal differences in technical difficulties and the amount of radiation exposure during lumbar TFESI. Key words: Transforaminal epidural steroid injection, complication, intravascular injection, Whitacre needle, Quincke needle, procedure time, radiation, digital subtraction angiography