Predictive parameters for successful indirect decompression of the lateral lumbar interbody fusion (LLIF) surgery

Background: Preoperative radiographic parameters in selecting the best surgical candidates for indirect decompression in the lateral lumbar interbody fusion (LLIF) surgery is considered one of the important concerns; there is a paucity of literature concerning this topic. This study aimed to find preoperative radiographic parameters that correlate with successful indirect decompression. Methods: We retrospectively reviewed patients who underwent LLIF surgery for various degenerative spine diseases at our institute. All patients included in the study had completed radiographs with preoperative and postoperative magnetic resonance imaging (MRI) within 3 months after surgery. Patients were categorized into success and failed indirect decompression using the cross-sectional area for pre and postoperative MRI scans. Various parameters were used to find an association for successful indirect decompression. Results: Sixty patients were included in our study with a total of 77 levels. Over two-thirds of patients (41/60, 68.3%) underwent oblique lateral lumbar interbody fusion or extreme lateral lumbar interbody fusion with posterior screw fixation. Of the 77 levels for which LLIF was performed, successful indirect decompression was attained in 38 levels and failed indirect decompression in 39 levels (49.3% success rate). Five parameters were significantly different between the success group and failed group. Only the cross-sectional area of the thecal sac (CSA) was significantly different as determined by a binary logistic mixed-effect regression model. Adding cut-point value to ROC curve of CSA, if CSA ≤ 106.97 mm2, it resulted in 82.14% sensitivity, and 72.41% specificity. Conclusion: LLIF showed significant improvement in average postoperative parameters. However, the cross-sectional area of the thecal sac (CSA) was the only parameter that inversely correlated with successful indirect decompression with LLIF. We concluded that even patients with severe spinal canal stenosis are good candidates for LLIF surgery owing to its indirect decompression.