Document Detail

Bilateral Pedicle Screw Fixation Provides Superior Biomechanical Stability in Transforaminal Lumbar Interbody Fusion: A Finite Element Study.
MedLine Citation:
PMID:  24983669     Owner:  NLM     Status:  Publisher    
BACKGROUND CONTEXT: Transforaminal lumbar interbody fusion (TLIF) is increasingly popular for the surgical treatment of degenerative lumbar disease. The optimal construct for segmental stability remains unknown.
PURPOSE: The purpose of this study was to compare the stability of fusion constructs using standard (C) and crescent-shaped (CC) polyetheretherketone (PEEK) TLIF cages with unilateral (UPS) or bilateral (BPS) posterior instrumentation.
STUDY DESIGN: Five TLIF fusion constructs were compared using finite element (FE) analysis.
METHODS: A previously validated L3-L5 FE model was modified to simulate decompression and fusion at L4-5. This model was used to analyze the biomechanics of various unilateral and bilateral TLIF constructs. The inferior surface of the L5 vertebra remained immobilized throughout load simulation, and a bending moment of 10 Nm was applied on the L3 vertebra to recreate flexion, extension, lateral bending and axial rotation. Various biomechanical parameters were evaluated for intact and implanted models in all loading planes. The study was supported by a grant from our institution. The authors do not have any relevant disclosures of potential conflicts of interest related to this study.
RESULTS: All reconstructive conditions displayed decreased motion at L4-5. Bilateral posterior fixation conferred greater stability when compared to unilateral fixation in left lateral bending. Over 50% of intact motion remained in left lateral bending with unilateral posterior fixation compared to less than 10% when bilateral pedicle screw fixation was used. Posterior implant stresses for unilateral fixation were six times greater in flexion and up to four times greater in left lateral bending compared to bilateral fixation. No effects on segmental stability or posterior implant stresses were found. An obliquely-placed, single standard cage generated the lowest cage-endplate stress.
CONCLUSIONS: TLIF augmentation with bilateral posterior fixation increases fusion construct stability and decreases posterior instrumentation stress. The shape or number of interbody implants does not appear to impact segmental stability when bilateral pedicle screws are used. Increased posterior instrumentation stresses were observed in all loading modes with unilateral pedicle screw/rod fixation, which may theoretically accelerate implant loosening or increase the risk for construct failure.
Divya V Ambati; Edward K Wright; Ronald A Lehman; Daniel G Kang; Scott C Wagner; Anton E Dmitriev
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-6-28
Journal Detail:
Title:  The spine journal : official journal of the North American Spine Society     Volume:  -     ISSN:  1878-1632     ISO Abbreviation:  Spine J     Publication Date:  2014 Jun 
Date Detail:
Created Date:  2014-7-1     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101130732     Medline TA:  Spine J     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2014 Elsevier Inc. All rights reserved.
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