Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

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BACKGROUND CONTEXT An important objective of lumbar spine surgery is to improve or restore sagittal alignment, as this is strongly linked to patient satisfaction and surgical outcomes. Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) can impact segmental and regional sagittal parameters. PURPOSE To evaluate if restoration of lordosis in MI-TLIF varies depending on the type of cage. STUDY DESIGN/SETTING Retrospective review of prospectively collected data. PATIENT SAMPLE Patients who underwent single level MI-TLIF with one of the following cages: tritanium oblique (static), expandable articulating (expandable), PEEK oblique (static) and PEEK articulating (static). OUTCOME MEASURES Change in total and segmental lordosis. METHODS Total and segmental lordosis was measured on upright lateral radiographs at two time points: preoperatively and immediate postoperatively. A Kruskall–Wallis test was conducted to compare the operative level (L4–L5vs. L5–S1) and a one-way ANOVA was conducted to compare total and segmental lordosis by type of cage. A 2×4 Mixed ANOVA test was conducted to assess the change in total and segmental lordosis by type of cage. RESULTS A total of 115 cases were included in this study of which 14 had a tritanium oblique cage, 14 had an expandable articulating cage, 30 had a PEEK oblique cage and 57 had a PEEK articulating cage. There was a statistically significant difference between the level operated based on the type of cage, with 78.6% of tritanium oblique group, 42.9% of the expandable articulating group, 83.3% of the PEEK oblique group and 61.4% of the peek articulating group being L4–L5 fusions.The mean preoperative segmental lordosis was significantly different between the types of cages (p=.014), with means of 16.74+5.91 (tritanium oblique), 14.93+5.52 (expandable articulating), 19.07+6.91 (PEEK oblique) and 20.70+6.61 (PEEK articulating) with a significant difference between the expandable articulating and PEEK articulating cages (p=.018) seen on post-hoc multiple comparisons. The mean postoperative segmental lordosis was not significantly different between the types of cages (p=.136), with means of 16.81+4.60 (tritanium oblique), 17.19+4.36 (expandable articulating), 19.80+6.82 (PEEK oblique) and 20.37+6.62 (PEEK articulating). The mean preoperative total lordosis was not significantly different between the types of cages (p=.070), with means of 55.13+11.29 (tritanium oblique), 49.57+11.35 (expandable articulating), 49.70+11.30 (PEEK oblique) and 55.84+12.14 (PEEK articulating). The mean postoperative total lordosis was not significantly different between the types of cages (p=.197), with means of 49.61+10.54 (tritanium oblique), 48.75+12.19 (expandable articulating), 49.10+10.49 (PEEK oblique) and 53.37+9.95 (PEEK articulating).The results of the mixed ANOVA showed that neither the change in segmental lordosis (P=.423), nor the change in total lordosis (P=.213) was statistically different between the types of cages. CONCLUSIONS The type of cage does not affect the change in total or segmental lordosis in MI-TLIF.