Figure 1.

Preoperative planning. Confirmation of the anatomy around the anterior portion of L5-S1 disc is mandatory using MRI (a, b), abdominal CT angiography (c, d), and reconstructed sagittal CT scan (e,f). (a) The anatomical window should be wide enough (a), and OLIF51 should not be performed when the vessels are congested in front of the disc (b). Abdominal CT angiography provides the information around the L5-S1 disc: (c) Adequate opening with good indication for OLIF51. (d) The left common iliac vein runs over the disc, and the indication for OLIF 51 must be carefully discussed. Confirmation of the relative location of L5-S1 space to the pubic symphysis is also essential in evaluating the preoperative approach to the L5-S1 disc space. If the direction of the L5-S1 disc goes under the pubic symphysis (e), OLIF51 approach is impossible compared with the usual direction (f).