Accuracy of the lateral cage placement under intraoperative C-arm fluoroscopy in oblique lateral interbody fusion

Abstract

BACKGROUND: In oblique lateral interbody fusion (OLIF), the lateral cage enters into the disc space obliquely, and is then turned to the true lateral direction to achieve a lateral lumbar interbody fusion. The OLIF cage is sometimes placed asymmetrically although it seemed to be placed accurately on intraoperative C-arm images. The present study aimed to investigate the accuracy of cage placement and its effect on the radiological outcome in OLIF. METHODS: This study involved a retrospective radiological analysis of 127 lateral cages in 75 consecutive OLIF patients. The cage deviations from the midline and cage obliquity were evaluated using three sets of images: (1) intraoperative C-arm fluoroscopy, (2) postoperative standing radiographs, and (3) postoperative computed tomography (CT). RESULTS: The mean cage deviation from the midline was measured as 2.5 +/- 2.7 mm on intraoperative C-arm images, but was found to be more deviated on postoperative radiographs and CT (5.4 +/- 3.8 mm and 3.8 +/- 3.7 mm: P = 0.000 and 0.005, respectively). The cage obliquity on the intraoperative lateral C-arm was minimal in 26 (20.5%) cases, mild in 69 (54.3%), and moderate in 32 (25.2%), but was found to be more obliquely on postoperative radiographs as minimal in 9 (7.1%), mild in 55 (43.3%), and moderate in 63 (49.6%) (P < 0.001). Anterior/posterior disc heights, disc lordotic angle, fusion rate, and cage subsidence rate were not different according to cage obliquity (all P > 0.05). CONCLUSIONS: Cage deviation from the midline and obliquity is underestimated on intraoperative C-arm images in OLIF. Although minimal cage deviation and obliquity did not affect the radiological outcome, great care should be made for the orthogonal cage insertion.