Anatomical Flow Pattern of Contrast in Lumbar Epidural Space: A Human Study with a Midline vs. Parasagittal Interlaminar Approach under Fluoroscopy.

BACKGROUND Epidural injections for managing chronic back pain are one of the most commonly performed interventions; however, controversy continues regarding the most effective method of epidural injections. A ventral distribution of epidural injected drug plays a significant role in its effectiveness. OBJECTIVE To determine the distribution of a drug in the epidural space after parasagital and midline epidural injection. SETTING Academic hospital. STUDY DESIGN In randomized double-blind clinical trial, patients with a diagnosis of low back pain (LBP) and unilateral lumbosacral radicular pains were randomized to receive drug through either parasagital or midline approach. METHODS Patients were assessed for anterior epidural spread of contrast under fluoroscopy in anteroposterior and lateral views. After epidural space confirmation, triamcinolone (80 mg) plus bupivacain was injected and patients were followed up for 2 weeks. RESULTS Fifty-six patients enrolled in the study. Successful infiltration of the drug into the ventral epidural space was successfully achieved in 75% of cases in the parasagital group but in only 25% of the cases in using a midline approach. Effective pain relief (numeric rating scale [NRS] < 3) was observed in 76.5% of patients in the parasagital group and 24.5% of patients in the midline group (P = 0.001) at 2 weeks. Number of patients with improved disability (measured by Oswestry Disability Index [ODI] < 20%) was significantly higher in the parasagital group (78%) compared to the midline group (26%) at 2 weeks (P = 0.002). LIMITATIONS The results of the current study should be interpreted in relation to the study design and future studies should include larger patient numbers and longer follow-up time. However, the results are consistent with previous studies. CONCLUSION Parasagital epidural injection showed higher infiltration of the drug to the ventral epidural space compared to the midline approach. The higher infiltration of the ventral epidural space provides better improvement of clinical disability and pain in the parasagital group.