Subsidence of PEEK Interbody

Presented at SMISS Annual Forum 2016
By Robert Isaacs MD
With

Disclosures: Robert Isaacs MD A; NuVasive. B; NuVasive, Providence Medical Technology. C; Association for Collaborative Spine Research. D; SafeRay Spine, LLC, SafeWire, LLC, VilaSpine LTD, Vertera Spine, Providence Medical Technol

Introduction

The purpose of this study was to investigate the incidence of subsidence in a single institution series and investigate relationship between subsidence and intraoperative endplate breach. 

Aims/Objectives

Extreme lateral interbody fusion (XLIF) has become an accepted alternative to anterior or posterior approaches to the lumbar spine. Benefits of this are numerable, however, while subsidence remains a major concern, it has been less well characterized while utilizing the XLIF approach. 

Methods

A single center retrospective review of patients undergoing XLIF from 2008 to 2012 was performed which showed 164 operative thoracolumbar levels in 45 patients with either a two-staged or stand-alone XLIF. Intra-operative images were taken and post-operative films performed at intervals from 6 weeks to a year post-operatively with a mean interval from fusion to assessment of subsidence of 7.3 months. 

Results

Subsidence occurred in 69% of patients at any level, and 38% of total levels. 23% of levels had radiographic evidence of intraoperative endplate violation. 46.4% of levels with endplate violation developed severe subsidence, versus 13.2% of levels without endplate violation. 71.8% of levels with endplate violation developed subsidence of any severity, while 27.3% of levels without endplate violation developed any radiographic evidence of subsidence (p < 0.0001 for all comparisons). Direction of endplate violation (inferior body vs. superior) was associated with a correlated direction of subsidence (p < 0.0001). Subsidence was not associated with level of fusion, age, construct length, or delayed instrumentation. After correcting for sex, age, percutaneous instrumentation delay of greater than 7 days, and construct length, the presence of an intraoperative endplate violation increased the risk of subsidence by more than 770% (OR: 7.77, p < 0.0001). When the same technique was used to predict severe subsidence, intraoperative endplate violation increased the risk of severe subsidence by more than 660% (OR: 6.62, p < 0.0001). 

Conclusions

Intraoperative endplate violation during extreme lateral interbody fusion is a major risk factor for the development of subsidence, as it predicts both subsidence direction and severity.