Fusion rate for stand-alone lateral lumbar interbody fusion: a systematic review

Background: Lateral lumbar interbody fusion (LLIF) is used to treat multiple conditions, including spondylolisthesis, degenerative disc disorders, adjacent segment disease, and degenerative scoliosis. Although many advocate for posterior fixation with LLIF, stand-alone LLIF is increasingly being performed. Yet the fusion rate for stand-alone LLIF is unknown.

Purpose: Determine the fusion rate for stand-alone LLIF.

Study design: Systematic review.

Methods: We queried Cochrane, EMBASE, and MEDLINE for literature on stand-alone LLIF fusion rate with a publication cutoff of April 2020. LLIF surgery was considered stand-alone when not paired with supplemental posterior fixation. Cohort fusion rate differences were calculated and tested for significance (p<0.05). All reported means were pooled.

Results: A total of 2,735 publications were assessed. Twenty-two studies met inclusion criteria, including 736 patients and 1,103 vertebral levels. Mean age was 61.7 years with BMI 26.5 kg/m². Mean fusion rate was 85.6% (range, 53.0%-100.0%), which did not differ significantly by number of levels fused (1-level, 2-level, and ≥3-level). Use of rhBMP-2 was reported in 39.3% of subjects, with no difference in fusion rates between studies using rhBMP-2 (87.7%) and those in which rhBMP-2 was not used (83.9%, odds ratio=1.37, p=0.448). Fusion rate did not differ with the addition of a lateral plate, or by underlying diagnosis. All-complication rate was 42.2% and mean reoperation rate was 11.1%, with 2.3% reoperation due to pseudarthrosis. Of the studies comparing stand-alone to circumferential fusion, pooled fusion rate was found to be 80.4% versus 91.0% (p=0.637).

Conclusions: Stand-alone LLIF yields high fusion rates overall. The wide range of reported fusion rates and lower fusion rates in studies involving subsequent surgical reoperation highlights the importance of proper training in this technique and employing a rigorous algorithm when indicating patients for stand-alone LLIF. Future research should focus on examining risk factors and patient-reported outcomes in stand-alone LLIF.