Cage Obliquity and Radiological Outcomes in Oblique Lateral Interbody Fusion

Study Design. Retrospective radiological study.Objective. This study aimed to examine whether cage obliquity affects radiological outcomes in oblique lateral interbody fusion (OLIF).Summary of Background Data. The OLIF cage enters the disk space in the oblique direction and is then turned to the true orthogonal orientation. However, orthogonal cage placement is often hindered by cage rotation limitations. Few studies have examined the degree of cage obliquity and its effects in OLIF.Materials and methods. This study involved 171 levels in 118 consecutive patients who underwent OLIF between L2-L3 and L4-L5 with a minimum two-year follow-up. Cage obliquity was divided into three groups on postoperative axial computed tomography images; cage obliquity <10 degrees (group 1), cage obliquity >= 10 degrees and <20 degrees (group 2), and cage obliquity >= 20 degrees (group 3). The radiological outcomes included anterior/posterior disk height, intervertebral disk angle, foraminal height, fusion, and cage subsidence. Postoperative complications related to cage obliquity were examined.Results. The mean cage obliquity of the 171 cages was 11.3 +/- 6.9 degrees. Cage obliquity was greater at the L4-L5 level (13.4 +/- 6.4 degrees) than at other levels (L2-L3 and L3-L4: 6.5 +/- 7.0 degrees and 10.1 +/- 6.2 degrees, respectively) ( P <0.05). There were no significant differences in radiological outcomes among the groups. There were two cases of postoperative contralateral neurological symptoms in group 3.Conclusions. Our study showed that the orthogonal cage rotation in OLIF achieved adequate lateral cage placement. Although accurate cage rotation can be limited at the lower lumbar segments, radiological outcomes were not affected by cage obliquity.