Transforaminal versus parasagittal interlaminar epidural steroid injection in low back pain with radicular pain: a randomized, double-blind, active-control trial.

BACKGROUND Epidural injections are the most common minimally invasive intervention used to manage low back pain with lumbosacral radicular pain. It can be delivered through either transforaminal (TF), interlaminar, or caudal approaches. The TF approach is considered more efficacious than the interlaminar approach probably because of ventral epidural spread. However, catastrophic complications reported with the TF approach have raised concerns regarding its use. These concerns regarding the safety of the TF approach lead to the search for a technically better route with lesser complications with drug delivery into the ventral epidural space. The parasagittal interlaminar (PIL) route is reported to have good ventral epidural spread. However, there is a paucity of literature comparing the effectiveness of PIL with TF. OBJECTIVES To compare effectiveness of PIL and TF epidural injections for managing low back pain with lumbosacral radicular pain. STUDY DESIGN Randomized, double-blind, active-control study. SETTING Interventional pain management clinic in a tertiary care center in India. METHODS Sixty-two patients were randomized to receive fluoroscopically guided epidural injection of methylprednisolone (80 mg) either through the PIL (n = 32) or TF (n = 30) approach. Patients were evaluated for effective pain relief (≥ 50% from baseline) by 0 - 100 visual analogue scale (VAS) and functional improvement by Modified Oswestry Disability Questionnaire (MODQ) at 2 weeks, 1, 2, 3, 6, 9, and 12 months. Patients who failed to respond to the treatment or when the patient's response deteriorated received additional injection of same injectate, dose, and approach. Only if the pain returns should there be a maximum of 3 injections. Other outcome measures were overall VAS and MODQ, number of injections, and presence of ventral and perineural spread. RESULTS Effective pain relief (≥ 50% pain relief from baseline on VAS) was observed in 76% (90% CI 60.6 - 88.5%) of patients in the TF group and 78% (90% CI 62.8 - 89.3%) of patients in the PIL (P = 1.00) group at 3 months. The pain relief survival period was comparable in both groups (P = 0.98). Significant reduction in VAS and improvement in MODQ were observed at all time points post-intervention compared to baseline (P < 0.001) in both groups. On average, patients in the PIL group received 1.84 and patients in the TF group received 1.92 procedures annually. The majority received injection at L4-L5 intervertebral level (24 in TF and 23 in PIL). Ventral epidural spread was comparable in both groups (PIL - 91.6% and TF - 89.6%). No major complications were encountered in either group; however, initial intravascular spread of contrast was observed in 3 patients in the TF group. LIMITATIONS Limitations included lack of documentation of adjuvant analgesic drug therapy and procedures performed by a single experienced interventionalist. CONCLUSIONS Epidural injection delivered through the PIL approach is equivalent in achieving effective pain relief and functional improvement to the TF approach for the management of low back pain with lumbosacral radicular pain. The PIL approach can be considered a suitable alternative to the TF approach for its equivalent effectiveness, probable better safety profile, and technical ease. TRIAL REGISTRATION CTRI/2012/08/002938.