Evaluation of iliac screw, S2 alar-iliac screw and laterally placed triangular titanium implants for sacropelvic fixation in combination with posterior lumbar instrumentation: a finite element study

Gloria Casaroli, Fabio Galbusera, Ruchi Chande, Derek Lindsey, Ali Mesiwala, Scott Yerby, Marco Brayda-Bruno

Research output: Contribution to journalArticle

Abstract

Purpose: This study aimed to implement laterally placed triangular titanium implants as a technique of sacropelvic fixation in long posterior lumbar instrumentation and to characterize the effects of iliac screws, S2 alar-iliac screws and of triangular implants on rod and S1 pedicle screw stresses. Methods: Four female models of the lumbopelvic spine were created. For each of them, five finite element models replicating the following configurations were generated: intact, posterior fixation with pedicle screws to S1 (PED), with PED and iliac screws (IL), with PED and S2 alar-iliac (S2AI) screws, and with PED and bilateral triangular titanium implants (SI). Simulations were conducted in compression, flexion–extension, lateral bending and axial rotation. Rod stresses in the L5-S1 segment as well as in the S1 pedicle screws were compared. Results: One anatomical model was not simulated due to dysmorphia of the sacroiliac joints. PED resulted in the highest implant stresses. Values up to 337 MPa in lateral bending were noted, which were more than double than the other configurations. When compared with IL, S2AI and SI resulted in lower stresses in both screws and rods (on average 33% and 41% for S2AI and 17% and 50% for SI). Conclusions: Implant stresses after S2AI and SI fixations were lower than those attributable to IL. Therefore, pedicle screws and rods may have a lower risk of mechanical failure when coupled with sacropelvic fixation via S2AI or triangular titanium implants, although the risk of clinical loosening remains an area of further investigation. Graphical abstract: These slides can be retrieved under Electronic Supplementary Material.[Figure not available: see fulltext.].

Original languageEnglish
Pages (from-to)1724-1732
Number of pages9
JournalEuropean Spine Journal
Volume28
Issue number7
DOIs
Publication statusPublished - Jul 1 2019

Keywords

  • Alar-iliac screws
  • Finite element analysis
  • Iliac screws
  • Sacroiliac joint
  • Sacropelvic fixation
  • Triangular implants

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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