Objective. To evaluate the effectiveness of a modified interlaminar (MIL) approach for accessing ventral epidural space compared with the transforaminal (TF) approach.

Study Design. Randomized double blinded control trial

Methods. Eighty-four patients with lumbar radicular pain were randomly assigned into two groups in which drug delivery to the ventral epidural space was performed through either the MIL (n = 42) or the TF approach (n = 42). Within each group, subgroups were classified according to the dominant pathology as assessed by magnetic resonance imaging (MRI): bulging disc, herniated nucleus pulposus (HNP), and foraminal stenosis. Degenerative changes such as scoliosis and facet hypertrophy was also evaluated.

Results. The overall accessibility to the ventral epidural space was similar between the two groups. In cases with foraminal stenosis, the success rate of ventral epidural spreading was significantly higher in the MIL group compared with the TF group (TF approach = 50.00% vs MIL approach = 100.00%, P = 0.013). Medial spread of contrast was more dominant in the MIL group ( P < 0.001). There was no significant difference between the two groups in overall clinical outcome. The total success rate of accessing the ventral epidural space in degenerative bony changes was higher in the MIL group than in the TF group (TF approach = 57.1% vs MIL approach = 84.6%), but the difference was not statistically significant.

Conclusion. In cases where access to the ventral epidural space by conventional approach is limited, our MIL approach can be considered a suitable alternative, especially in the case of foraminal stenosis.

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