Analysis of dispersion of lumbar interlaminar epidural injectates

provided the original work is properly cited. CC It is recognized that because most lumbar disc herniations occur posterior to the vertebrae, inflammation arises primarily in the anterior epidural space at the site of the disc herniation [1]. Therefore, deposition of steroids in the anterior epidural space directly at the site of inflammation has been the preferred treatment [2]. Until recently, the transforaminal approach has been considered to be the most target-specific, with the least volume necessary to reach the primary site of pathology (the anterior epidural spaces), compared to interlaminar approaches [3,4]. However, the transforaminal approach presents a higher risk of severe adverse events for patients. We have clearly confirmed through an imaging study, whether or not lumbar interlaminar epidural injectates are able to reach the anterior epidural space. After informed, written consent was obtained, 43 patients who suffered from lower back pain without radiculopathy due to degenerative disc disease or internal disc disruption were enrolled in an Institutional Review Board-approved, prospective, controlled, single-blinded study. The male to female ratio was 1 : 2, and the mean age was 61.9 years. Lower back pain in all study patients was treated with lumbar interlaminar epidural steroid injections (LIESIs). Patients with extruded disc rupture, severe spinal stenosis with neurogenic claudication, severe spondylolisthesis and history of spinal surgery or intervention, such as percutaneous vertebroplasty or kyphoplasty, were excluded in order to minimize the influence of anatomical deformities that could affect the dispersion pattern of lumbar interlaminar epidural injectates. The study patients were randomly divided into four groups (A, B, C and D) according to the total volume of injectate administered. Injectates were composed of 0.5% lidocaine, 20 mg of triamcinolone, and radiocontrast dye (Isovist-240, Schering) and were administered as follows: Group A received 5 ml (3 ml of 0.5% lidocaine, 20 mg of triamcinolone [0.5 ml], and 1.5 ml of radiocontrast dye), Group B received 7.5 ml (5 ml of 0.5% lidocaine, 20 mg of triamcinolone, and 2 ml of radiocontrast dye), and Group C received 10 ml (7 ml of 0.5% lidocaine, 20 mg of triamcinolone, and 2.5 ml of radiocontrast dye). To clarify the effect of position change on the dispersion of the injectates, Group D received 7.5 ml (5 ml of 0.5% lidocaine, 20 mg of triamcinolone, and 2 ml of radiocontrast dye) and assumed a supine position soon after the procedure until the computed tomography (CT) scan was taken. After 20 minutes, all patients were re-scanned from the upper endplate level of the L1 body to the S2 body level, using CT to a thickness of three millimeters. The physicians divided each vertebra into two compartments; an upper and a lower. One intervertebral disc was regarded as one compartment. Therefore, the total number of compartments was 16; from the L1 upper endplate level to the S1 upper body level (Fig. 1). The results show that there were no statistical differences between Groups A, B, and C in the degree of dispersion of the injectates anteriorly and posteriorly in the epidural space (P > 0.05) and that there were no statistical differences between Groups B and D (P > 0.05). However, in all of the groups, the degree of dispersion of the injectates within the posterior epidural space was greater than that within the anterior epidural space. No patient in this study experienced any infection, headache, intravascular injection, reaction to the contrast material and steroid, or subarachnoid injection.