Segmental and overall lumbar lordosis following single-level minimally invasive transforaminal lumbar interbody fusion: a systematic review and meta-analysis

Introduction: Due to heterogeneity in previous studies, the effect of MI-TLIF on postoperative segmental lordosis (SL) and lumbar lordosis (LL) remains unclear. Given this evidence gap, we perform a systematic review and meta-analysis of studies reporting lordotic outcomes after single-level MI-TLIF. In addition, we perform a meta-regression to identify preoperative factors associated with lordosis after surgery.

Methods: This systematic review was conducted according to PRISMA guidelines. PubMed, MEDLINE, CENTRAL, EMBASE, and Scopus were searched. Studies describing single-level MI-TLIF for degenerative lumbar etiologies with at least a sample size of 10 patients were included. Random effects meta-analysis was used for data synthesis, and I2 to assess heterogeneity. Primary outcomes were change in SL and/or change in overall LL.

Results: Thirty-five studies spanning 1,935 patients met inclusion criteria. Most studies were retrospective case series (n=23, 66%), followed by retrospective (n=9, 26%), and prospective cohort studies (n=3, 9%). Twenty-five (71%) cases used static interbody devices, 5 (14%) used expandable devices, and 5 (15%) included both device types. Most studies used bilateral pedicle screw fixation (n=23, 66%), although 5 (14%) used unilateral, and 7 (20%) used both. Mean sample size was 55 (range 13-171), mean age was 59.4 (SD: 10.5), and mean BMI was 27.0 (4.6). Mean follow-up was 21.4 (7.4, range: 6-20.5) months. On random effects modeling, patients experienced a significant increase in segmental lordosis (standardized mean difference [SMD]: 2.2, [95% CI: 1.3, 3.1], p< 0.001) and overall lumbar lordosis (SMD: 2.8, [95% CI: 0.8, 4.8], p< 0.001) at latest follow-up. On meta-regression, preoperative SL (β: -0.24° [95% CI: -0.42°, -0.05°, p=0.01) was predictive of change in SL, whereas preoperative LL (β: -0.53° [95% CI: -0.81°, -0.25°, p=0.009) and use of an expandable cage (β: 6.56° [95% CI: 1.0°, 12.2°, p=0.02) was predictive of change in LL

Conclusion : Current evidence investigating lordotic outcomes following single-level MI-TLIF is highly variable. Variation in levels treated, surgical techniques, interbody devices, and surgical adjuncts all contribute to lordotic outcomes. Despite the significant heterogeneity among included studies, our results suggest that single-level MI-TLIF is generally lordosing, with preoperative alignment and interbody device type as possible predictors of postoperative lordosis.