Predictors of Postoperative Segmental and Overall Lumbar Lordosis in Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Consecutive Case Series

Study Design Retrospective Case-Series. Objectives Due to heterogeneity in previous studies, the effect of MI-TLIF on postoperative segmental lordosis (SL) and lumbar lordosis (LL) remains unclear. Therefore, we aim to identify radiographic factors associated with lordosis after surgery in a homogenous series of MI-TLIF patients. Methods A single-center retrospective review identified consecutive patients who underwent single-level MI-TLIF for grade 1 degenerative spondylolisthesis from 2015-2020. All surgeries underwent unilateral facetectomies and a contralateral facet release with expandable interbody cages. PROs included the ODI and NRS-BP for low-back pain. Radiographic measures included SL, disc height, percent spondylolisthesis, cage positioning, LL, PI-LL mismatch, sacral-slope, and pelvic-tilt. Surgeries were considered "lordosing" if the change in postoperative SL was & GE; +4 & DEG; and "kyphosing" if & LE; -4 & DEG;. Predictors of change in SL/LL were evaluated using Pearson's correlation and multivariable regression. Results A total of 73 patients with an average follow-up of 22.5 (range 12-61) months were included. Patients experienced significant improvements in ODI (29% & PLUSMN; 22% improvement, P < .001) and NRS-BP (3.3 & PLUSMN; 3 point improvement, P < .001). There was a significant increase in mean SL (& UDelta;3.43 & DEG; & PLUSMN; 4.37 & DEG;, P < .001) while LL (& UDelta;0.17 & DEG; & PLUSMN; 6.98 & DEG;, P > .05) remained stable. Thirty-eight (52%) patients experienced lordosing MI-TLIFs, compared to 4 (5%) kyphosing and 31 (43%) neutral MI-TLIFs. A lower preoperative SL and more anterior cage placement were associated with the greatest improvement in SL (& beta; = -.45 & DEG; P = .001, & beta; = 15.06 & DEG; P < .001, respectively). Conclusions In our series, the majority of patients experienced lordosing or neutral MI-TLIFs (n = 69, 95%). Preoperative radiographic alignment and anterior cage placement were significantly associated with target SL following MI-TLIF.