Static vs. Expandable Interbody Devices in Minimally Invasive Transforaminal Lumbar Interbody Fusion: Comparison of Radiographic and Functional Outcomes

Presented at SMISS Annual Forum 2018
By Dil Patel BS
With Benjamin Khechen BA, Brittany Haws MD, Mundeep Bawa , Harmeet Bawa , Jordan Guntin BS, Kaitlyn Cardinal BS, Andrew Block BS, Kern Singh MD,

Disclosures: Dil Patel BS None Benjamin Khechen BA None, Brittany Haws MD None, Mundeep Bawa None, Harmeet Bawa None, Jordan Guntin BS None, Kaitlyn Cardinal BS None, Andrew Block BS None, Kern Singh MD A; CSRS Resident Grant. B; DePuy, Zimmer, Stryker, CSRS, ISASS, AAOS, SRS, Vertebral Column - ISASS. D; Avaz Surgical, LLC, Vital 5, LLC. F; Zimmer, Stryker, Pioneer, Lippincott Williams & Wilkins, Th,


Limited studies have analyzed the differences in radiographic and patient reported outcomes (PROs) between expandable and static interbody devices.


This study aims to evaluate differences in radiographic parameters and PROs following single-level minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) between static and expandable interbody devices.


Patients that underwent primary, single-level MIS TLIF between 2014-2017 were retrospectively identified. Only patients that had completed at least six months of postoperative follow-up were included. Radiographic measurements including lumbar lordosis (LL), segmental lordosis (SL), disc height (DH) and foraminal height (FH) were performed on lateral radiographs before and after MIS TLIF with a static or expandable articulating interbody device. Radiographic outcomes and PROs were compared using paired and unpaired Student’s t-test.


60 patients undergoing MIS TLIF were included, with 30 patients receiving expandable interbody devices and 30 patients receiving static interbody devices. Both static and expandable device cohorts demonstrated significant increases in DH, FH, and LL. Additionally, patients receiving an expandable device demonstrated a significant increase in SL. When comparing improvements in radiographic measures, the expandable device cohort exhibited significantly greater improvement in DH and FH at final follow-up. When examining patient outcomes, both surgical cohorts experienced significant improvements in ODI, and VAS back and leg at 6-months postoperatively.


Undergoing MIS TLIF with an expandable interbody device led to a greater increase of DH than with a static interbody device. Patients reported significant improvements in PROs following MIS TLIF in both expandable and static interbody device cohorts. However, no differences in improvement were demonstrated between surgical cohorts. Although use of expandable interbody device led to greater increases in DH, this may not correlate with superior patient outcomes. As such, patients undergoing MIS TLIF can expect similar improvements in PROs, whether receiving a static or expandable interbody device.