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 I 2 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/m 2 , 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.