Comparison of unremoved intervertebral disc location between two lateral lumbar interbody fusion (LLIF) techniques.

To compare location and amount of unremoved intervertebral disc between XLIF and OLIF. Postoperative magnetic resonance images (MRI) of patients who underwent XLIF and OLIF for degenerative spine diseases were reviewed. An axial cut T2-weight image which was the middle cut of operated disc space was selected. We divided disc area into 5 zones: central, left anterior, left posterior, right anterior, and right posterior. Disc area was measured using Picture Archiving and Communication System (PACs) program. The angle of intervertebral cage was also measured. A total of 61 levels of XLIF from 51 patients and 62 levels of OLIF from 34 patients were included. The area of unremoved disc at left anterior, right anterior, and left posterior zones of OLIF were significantly more than XLIF (55.7±41.5 vs 29.8±33.3 mm 2 , 57.9±43.6 vs 34.1±33.1 mm 2 and 50.5±41.8 vs 31.5±35.9 mm 2 respectively; P<0.01). No significant differences were found at the right posterior and central zones. A 9.2º±6.1º and 0.7º±4.9º cage angulation from left anterior to right posterior was found in OLIF and XLIF respectively with statistical significance. Our study found a greater area of unremoved disc in OLIF compared to XLIF. The common locations were in the contralateral side of the surgical approach, right anterior in OLIF, and right posterior in XLIF. The greater area of the unremoved disc in the anterior zone after OLIF due to oblique corridor to disc space may cause cage malposition. Meticulous disc removal should be done especially in OLIF to prevent complications.