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

Objective: Because of heterogeneity in previous studies, the effect of minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) on postoperative segmental lordosis (SL) and lumbar lordosis (LL) remains unclear. Given this evidence gap, the authors performed a systematic review and meta-analysis of studies reporting lordotic outcomes after single-level MI-TLIF. The authors also performed a meta-regression to identify preoperative factors associated with lordosis after surgery and assessed correlations between lordotic changes and patient-reported outcomes.

Methods: In this systematic review, PubMed, Medline, CENTRAL, EMBASE, and Scopus were searched for studies describing single-level MI-TLIF for degenerative lumbar etiologies with at least 10 patients. Random-effects meta-analysis was used for data synthesis and I2 was used to assess heterogeneity. Primary outcomes were changes in SL and/or changes in overall LL.

Results: Thirty-five studies comprising 1935 patients were included: 23 (66%) retrospective case series, 9 (26%) retrospective, and 3 (9%) prospective cohort studies. Twenty-five (71%) studies evaluated static interbody devices, 5 (14%) expandable devices, and 5 (14%) both device types. Thirty (86%) studies used bilateral pedicle screw fixation, 2 (6%) used unilateral screw fixation, and 3 (9%) included both techniques. The mean (range) sample size was 55 (13-171) patients, mean ± SD age was 59.5 ± 10.6 years, mean ± SD BMI was 26.9 ± 4.6 kg/m2, and mean ± SD (range) length of follow-up was 21.4 ± 4.3 (6.0-63.7) months. On random-effects modeling, patients experienced a significant increase in SL (standardized mean difference [SMD] +2.2°, 95% CI 1.3°-3.1°, p < 0.001) and overall LL (SMD +2.8°, 95% CI 0.8°-4.8°, p < 0.001) at the latest follow-up. On meta-regression, preoperative SL (β = -0.24°, 95% CI -0.42° to -0.05°, p = 0.01) was predictive of a change in SL, whereas preoperative LL (β = -0.53°, 95% CI -0.81° to -0.25°, p = 0.009) and use of an expandable cage (β = 6.56°, 95% CI 1.0°-12.2°, p = 0.02) were predictive of a change in LL. Univariable meta-regression found that greater increases in SL were associated with larger reductions in postoperative leg pain (β = -1.03, 95% CI -1.6 to -0.45, p = 0.003); however, no significant associations were detected between changes in SL or LL and other clinical outcomes in either univariable or multivariable analyses.

Conclusions: Despite the significant heterogeneity among the included studies, these results suggest that single-level MI-TLIF is generally lordosis preserving, with preoperative alignment and interbody device type as possible predictors of postoperative lordosis.