Resident Physician NYU Langone Health New York, New York, United States
Introduction: It has been previously shown that expandable cages for transforaminal lumbar interbody fusion (TLIF) are associated with increased rates of subsidence. However, as lateral lumbar interbody fusion (LLIF) cages offer substantially larger footprints, this may offset the risks.
Methods: A retrospective, comparative study of consecutive adults undergoing LLIF with either static or expandable cages from 2013-2021. Demographics and surgical details were collected. Outcomes of interest included posterior disc height (PDH) restoration, subsidence, and fusions status. Follow-up were reported at minimum 6-months and 1-year.
Results: 187 LLIFs were included: 147 static vs. 40 expandable. Cohorts had no significant differences in age (63.0 v 64.8 years; p=0.305), gender (64.6% v 57.5% female; 0.408), BMI (29.5 v 29.4; p=0.883), smoking (11.6% v 5.0%; p=0.223), or osteoporosis (25.9% v 25.0%; p=0.911). Preoperative PDH was significantly greater (3.9 v 5.3 mm; p< 0.001) and percentage increase in PDH significantly smaller (118.5% v 86.2%; p=0.011) in the expandable cohort. There were no significant differences in change in PDH (3.2 v 3.6 mm; p=0.355), or anteroposterior position of LLIF (243.9 v 24.8; p=0.679). There were no significant differences in 6-month (6.8% v 10.2%; p=0.467) or 1-year (10.9% v 7.9%, p=0.588) subsidence rates. There was no significant difference in rate of fusion (92.4% v 96.8%; p=0.382). 39 static and 39 expandable remained after propensity matching for age (65.9 v 65.1; p=0.706), gender (71.8% v 58.9% female; p=0.234), BMI (29.2 v 29.4; p=0.867), smoking (10.3% v 5.1%; p=0.395), osteoporosis (21.6% v 25.6%; p=0.680), and preoperative PDH (5.2 v 5.3 mm; p=0.827). There were no significant differences in percent change in PDH (70.1% v 86.2%; p=0.410), 6-months (10.3% v 10.3%; p=1.000) and 1-year (15.4% v 10.3%; p=0.306) subsidence rates, or evidence of fusion at 1-year (94.9% v 96.8%; p=0.884).
Conclusion : Static and expandable cages offer similar PDH restoration depending on surgical goals. Expandable cages seem to be less prone to subsidence than smaller TLIF cage counterparts and offer similar fusion rates to static cages.
