A Radiographic Measurement of the Anterior Epidural Space at L4-5 Disc Level.

To observe the morphology character of the anterior epidural space at the L4-5 disc level and to provide an anatomical basis for safely and accurately performing a percutaneous endoscopic lumbar discectomy (PELD). Fifty-five cases with L5 S1 lumbar disc herniation were included in this study, and cases with L4-5 disease were excluded. When the puncture needle reached the epidural space at the L5 S1 level, iohexol was injected at the pressure of 50 cm H2 O during the PELD, then C-Arm fluoroscopy was used to obtain standard lumbar frontal and lateral images. The widths of epidural space at the level of the L4 lower endplate, the L5 upper endplate, as well as the middle point of the L4-5 disc were measured from the lumbar lateral X-ray film. Epidural space at the L4-5 disc plane performs like a trapezium chart with a short side at the head end and a long side at the tail end in the lumbar lateral X-ray radiograph, while the average widths of epidural space were 10.2 ± 2.5, 12.3 ± 2.3, and 13.8 ± 2.6 mm at the upper, middle, and lower level of the L4-5 disc. Understanding the morphological characteristics of epidural space will contribute to improving the safety of the tranforaminal percutaneous endoscopy technique.