Cage Subsidence and Fusion Rate in Extreme Lateral Interbody Fusion with and without Fixation

Objective To examine the subsidence rate in patients undergoing extreme lateral interbody fusion (XLIF) using data from a 2-year retrospective study to assess the effect of supplemental fixation on the stand-alone procedure. Methods Demographic and perioperative data for all patients who underwent XLIF for degenerative lumbar disorders between June 2012 and January 2016 were collected and divided into 4 groups: the stand-alone (SA), lateral fixation, unilateral pedicle screw, and bilateral pedicle screw (BPS) groups. The disk height (DH), lumbar lordotic (LL) angle, and segmental lordotic (SL) angle were measured preoperatively and 3 days, 3 months, 1 year, and 2 years postoperatively. Clinical outcomes were evaluated using Japanese Orthopaedic Association (JOA) and visual analog scale (VAS) scores. Fusion was defined according to computed tomography scan. Results There were 126 vertebrae in 107 patients treated. SL angle, LL angle, and DH significantly increased postoperatively in all groups. Although the preoperative and 2-year postoperative DHs in the SA group were similar, the other measures showed significant differences from baseline at each follow-up visit. No significant effects on SL angle or DH were found in any of the groups. A significant difference in the LL angle was found in the BPS group compared with the other groups. At the last follow-up, high-grade subsidence was found in 26.89% of all cases, the fusion rate was 85.71%, and the VAS and JOA scores were significantly improved in all groups. Conclusions Supplemental fixation did not significantly influence cage subsidence or SL angle. Only BPS fixation significantly improved the LL angle. The 2-year fusion rate was satisfactory.