The type of cage used in minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) can impact several goals of the procedure, including optimizing disc and foraminal height, interbody fusion, and sagittal balance.
Segmental lordosis (SL), lumbar lordosis (LL), posterior disc height (PDH) were compared using upright lateral radiographs obtained pre- and postoperatively. Impact of demographic (age, sex, and BMI), preoperative radiographic (SL, LL, and PDH) and operative factors (cage-type, cage-width, and cage-position) on radiographic outcomes were assessed.
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 = .389) or postoperatively (P = .613). A difference was seen in change in SL (P = .023), with the expandable articulating cage showing the greatest increase, and an improvement from pre- to postoperatively (P = .033). A significant difference was seen in change in LL (P = .050), with the static oblique and expandable articulating groups maintaining LL (P = .238 and P = .873), but the static articulating group showing decrease in LL (P < .0001). There was a significant difference in PDH pre- and postoperatively (P < .0001 and P = .045). All three cages increased in PDH (P < .0001), with the expandable articulating cage showing the greatest increase (P = .009). Regressions showed that preoperative SL was the only significant predictor of postoperative SL (P < .0001; R2 = 0.418) and change in SL (P < .0001; R2 = 0.247); preoperative LL of postoperative LL (P < .0001; R2 = 0.609) and change in LL (P < .0001; R2 = 0.227); and preoperative PDH of postoperative PDH (P < .0001; R2 = 0.360) and change in PDH (P < .0001; R2 = 0.299). Cage-type, cage-position, and cage-width were not significant predictors of radiographic parameters.
Preoperative radiographic parameters were predictors of postoperative parameters. While the static cages maintained SL, the expandable cage increased SL. The expandable cage had the lowest preoperative 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.