Needle Depth and Angle for Lumbar Interlaminar Epidural Injection Using Magnetic Resonance Imaging and C-Arm Measurements

Abstract

BACKGROUND: Interlaminar epidural injection (ILEI) is used to relieve low back pain, with or without radiating pain. The distance from the skin to the epidural space determines the needle depth and may be influenced by the patient’s body measurements. OBJECTIVES: The objective of this study was to investigate the correlation between needle depth for ILEI and patients’ body profiles, including weight, height, and body mass index (BMI), using magnetic resonance imaging (MRI) and also to compare the needle depth and angle between MRI and C-arm fluoroscopic images of ILEI. STUDY DESIGN: This was a retrospective study. SETTING: This study was conducted at a single Department of Anesthesiology and Pain Medicine of Konkuk University Medical Center. METHODS: This retrospective study reviewed patients who underwent MRI and ILEI. The needle depth and caudal angle were measured on the sagittal view of MRI and C-arm images for L3–L4, L4–L5, and L5–S1 ILEI. RESULTS: Overall, 386 patients were reviewed. For MRI, the mean value of the needle angle given caudally was 14.70, 12.06, and 11.33 for L3–4, L4–5, and L5–S1 ILEIs, respectively. Mean values of needle depth were 52.17, 52.09, and 47.91 mm for L3-4, L4-5, and L5–S1 ESIs, respectively. Height combined with weight and BMI had a higher correlation with needle depth than weight and height. In the comparison between MRI and fluoroscopy, needle depth at L5–S1 and caudal angle at L3–4 and L4–5 were significantly correlated. LIMITATIONS: This study was a retrospective study conducted at a single center. CONCLUSION: Height combined with weight and BMI can help estimate the optimal needle depth from the skin to the epidural space. Needle depth in L5–S1 and caudal angle in L3–4 and L4–5 of MRI were correlated with those of fluoroscopy of ILEI. KEY WORDS: Body mass index, epidural depth, obesity, morbid, injections, epidural, magnetic resonance imaging, C-arm fluoroscopic images, low back pain, umbosacral pain IRB approval was obtained from the Institutional Review Board of Konkuk University Hospital (IRB file No. 2020-04-011).