Authors: Avani Vaishnav; Joshua Wright-Chisem, MD; Michael Steinhaus, MD; Sravisht Iyer, MD; Steven McAnany, MD; Todd Albert, MD; Catherine Gang, MPH; Sheeraz Qureshi, MD, MBA (New York, NY)
Introduction: The type of cage used in MI-TLIF can impact several goals of the procedure, including optimizing disc and foraminal height, interbody fusion, and sagittal balance. Objective: To assess if cage type has an impact on immediate radiographic outcomes in single-level MI-TLIF. Method: Segmental Lordosis(SL), Lumbar Lordosis(LL), Posterior Disc Height(PDH) were compared using lateral radiographs obtained pre- and post-operatively. Impact of demographic(age, sex, BMI), pre-operative radiographic(SL, LL, PDH) and operative factors(cage-type, cage-width, cage-position) on radiographic outcomes was assessed. Results: Of the 154 patients included, 55 received a Static Oblique, 63 a Static Articulating, and 36 an Expandable Articulating cage. There was no significant difference in SL pre-(p=0.389) or post-operatively(p=0.613). A difference was seen in change in SL(p=0.023), with the expandable articulating cage showing the greatest increase, and an improvement from pre- to post-operatively(p=0.033). A significant difference was seen in change in LL(p=0.050), with the static oblique and expandable articulating groups maintaining LL(p=0.238 and p=0.873), but the static articulating group showing decrease in LL(p<0.0001). There was a significant difference in PDH pre- and post-operatively(p<0.0001 and p=0.045). All three cages increased in PDH(p<0.0001), with the expandable articulating cage showing the greatest increase(p=0.009). Regressions showed that pre-operative SL was the only significant predictor of post-operative SL(p<0.0001;R 2 =0.418) and change in SL(p<0.0001;R 2 =0.247); pre-operative LL of post-operative LL(p<0.0001 R 2 =0.609) and change in LL(p<0.0001;R 2 =0.227); and pre-operative PDH of post-operative PDH(p<0.0001;R 2 =0.360) and change in PDH(p<0.0001;R 2 =0.299). Cage-type, cage-position and cage-width were not significant predictors of radiographic parameters. Conclusion: Pre-operative radiographic parameters were predictors of post-operative parameters. While the static cages maintained SL, the expandable cage increased SL. The expandable cage had the lowest pre-operative PDH, likely reflective of the expandable technology allowing for cage-insertion even in collapsed disc spaces. The expandable articulating cage demonstrated benefit in increasing SL, maintaining LL and causing the greatest increase in PDH.