Static Versus Expandable Devices Provide Similar Clinical Outcomes Following Minimally Invasive Transforaminal Lumbar Interbody Fusion



Few studies have analyzed differences in radiographic parameters and patient-reported outcomes (PROs) between expandable and static interbody devices in patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS TLIF).


To evaluate differences in radiographic parameters and PROs following MIS TLIF between static and expandable interbody devices.


Patients undergoing primary, single-level MIS TLIF between 2014 and 2017 were retrospectively identified. 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.


Thirty patients received expandable interbody devices and 30 patients received static interbody devices. The expandable device cohort exhibited significantly greater improvement in DH and FH at final follow-up compared with those receiving a static device. Both device cohorts experienced significant improvements in PROs at 6 months post-operatively.


MIS TLIF with an expandable interbody device led to a greater increase of DH and FH than with a static interbody device. Patients undergoing MIS TLIF can expect similar improvements in PROs whether receiving a static or an expandable interbody device. Further studies are required to better understand improvements in clinical outcomes afforded by expandable interbody devices.

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Corresponding author

Correspondence to Kern Singh MD.

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Conflict of Interest

Benjamin Khechen, BA, Brittany E. Haws, MD, Dil V. Patel, BS, Joon S. Yoo, BA, Jordan A. Guntin, BS, Kaitlyn L. Cardinal, BS, and Sravisht Iyer, MD, declare that they have no conflicts of interest. Kern Singh, MD, reports royalties from Zimmer, Stryker, Pioneer, Lippincott Williams & Wilkins, Thieme, Jaypee Publishing, and Slack Publishing; stock ownership in Avaz Surgical, LLC, and Vital 5, LLC; board membership and a grant from Cervical Spine Research Society; board membership at the International Society for the Advancement of Spine Surgery, American Academy of Orthopaedic Surgeons, Scoliosis Research Society, and Vertebral Column–ISASS, all outside the submitted work.

Human/Animal Rights

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2013.

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Informed consent was waived from all patients for being included in this study.

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Level of Evidence: Level III: Therapeutic Study.

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Khechen, B., Haws, B.E., Patel, D.V. et al. Static Versus Expandable Devices Provide Similar Clinical Outcomes Following Minimally Invasive Transforaminal Lumbar Interbody Fusion. HSS Jrnl 16, 46–53 (2020).

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  • minimally invasive transforaminal interbody fusion
  • interbody device
  • expandable
  • static
  • patient-reported outcomes
  • radiographic outcomes
  • lordosis
  • disc height
  • foraminal height