Subsidence of PEEK Interbody

Presented at SMISS Annual Forum 2016
By Robert Isaacs MD

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


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. 


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. 


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. 


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). 


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.