Outcomes and Predictors of Subsidence After Expandable Cage in Minimally Invasive Transforaminal Lumbar Interbody Fusion

Thursday, June 1, 2023

8:30 AM – 6:15 PM

Location: Salons 7-8

Presenting Author (Person doing the Podium Present(s)

TS

Tejas Subramanian, BS

Hospital for Special Surgery, United States

View E-Poster

Co-Author(s)

PS

Pratyush Shahi, MBBS

Hospital for Special Surgery
New York, New York, United States
RM

Robert Merrill, MD

Hospital for Special Surgery, United States
OM

Omri Maayan, BS

Hospital for Special Surgery, United States
SP

Shane Pathania, BS

hospital for special surgery, United States
DS

Daniel Shinn, BE

Medical Student
hospital for special surgery, United States
AK

Ashley Kim, BA

hospital for special surgery, United States
EZ

Eric Zhao, BS

Hospital for Special Surgery, United States
KA

Kasra Araghi, BS

Research Fellow
Hospital for Special Surgery
Scottsdale, Arizona, United States
MS

Michael Steinhaus, MD

Fellow
hospital for special surgery
New York, New York, United States
AV

Avani Vaishnav, MBBS

hospital for special surgery, United States
SS

Sachin Shah, BS

United States
YO

Yahya Othman, MD

hospital for special surgery, United States
AS

Andre Samuel, MD

hospital for special surgery, United States
FL

Francis Lovecchio, MD

Fellow
Hospital for Special Surgery, United States
JD

James E. Dowdell, MD

Spine Fellow
Hospital for Special Surgery
New York, New York, United States
ES

Evan Sheha, MD

Hospital for Special Surgery, United States
SI

Sravisht Iyer, MD

Assistant Attending, Spine Surgery
Hospital for Special Surgery
New York, New York, United States
SQ

Sheeraz A. Qureshi, MD, MBA

Attending Surgeon
Hospital for Special Surgery
York, New York, United States

Submitter(s)

JD

James E. Dowdell, MD

Spine Fellow
Hospital for Special Surgery
New York, New York, United States

Disclosure(s):

Tejas Subramanian, BS: No financial relationships to disclose

Robert Merrill, MD: No financial relationships to disclose

Omri Maayan, BS: No financial relationships to disclose

Sravisht Iyer, MD: No financial relationships to disclose

Introduction: Expandable cage technology has been adopted in minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) to reduce the risks and optimize outcomes. Although subsidence is of particular concern when using expandable technology as force required to expand the cage can weaken the endplates, its rates, predictors, and outcomes lack evidence. We hypothesize that subsidence remains a radiological parameter and does not have a significant impact on the clinical outcomes.

Aims/

Objectives: To investigate predictors of subsidence in minimally invasive transforaminal lumbar interbody fusion with expandable cage.

Methods: Patients who underwent 1- or 2-level MI-TLIF using expandable cages for degenerative lumbar conditions and had a minimum follow-up of 1 year were included. Preoperative and immediate, early ( < 1 month), and late (up to 24 months) postoperative radiographs were reviewed. Subsidence was determined if the average anterior/posterior disc height decreased by >25% compared to the immediate postoperative value. Patient reported outcome measures (PROMs) including the Oswestry Disability Index (ODI), Visual Analog Scale (VAS), Short Form-12 (SF-12), and Patient-Reported Outcomes Measurement Information System (PROMIS) were collected and analyzed for differences at the early ( < 6 months) and late (>6 months) timepoints. Fusion was assessed by 1-year postoperative CT.

Results: A total of 148 patients were included (mean age 61 yrs, 86% 1-level, 14% 2-level). 22 (14.9%) demonstrated subsidence. Although statistically not significant, patients with subsidence were older with lower bone mineral density, higher BMI, and greater comorbidity burden. Subsided patients exhibited significantly longer operative time (p=0.02) and lower implant width (p < 0.01). There was no significant difference in PROMs between the groups at any timepoint. Long-term (>6m) patient acceptable symptom state (PASS) achievement rate was lower for subsided patients (53% vs 77%), although statistically not significant (p=0.065). There were no differences in complication, reoperation, or fusion rates.

Conclusions: 14.9% of patients experienced subsidence predicted by narrower implants. Although subsidence did not have a significant impact on PROMs and complication, reoperation, or fusion rates, it led to a lower PASS achievement rate at the >6-month timepoint.