Clinical Data

FEA: Sacropelvic Fixation, Stability and Instrument Stresses (Panico - Int J Spine Surg 2023b)

Stability and Instrumentation Stresses Among Sacropelvic Fixation Techniques With Novel Porous Fusion/Fixation Implants: A Finite Element Study

Panico M, Chande RD, Lindsey DP, Mesiwala A, Polly DW, Villa T, Yerby SA, Brayda-Bruno M, Galbusera F.
Int J Spine Surg. 2023 Aug;17(4):598-606. [Epub 2023 Jul 17].
DOI: 10.14444/8481. PMID: 37460239; PMCID: PMC10478686.
Erratum in: Int J Spine Surg. 2024 Mar 4;18(1):119.


Background: Sacropelvic fixation is frequently combined with thoracolumbar instrumentation for correcting spinal deformities. This study aimed to characterize sacropelvic fixation techniques using novel porous fusion/fixation implants (PFFI).

Methods: Three T10-pelvis finite element models were created: (1) pedicle screws and rods in T10-S1, PFFI bilaterally in S2 alar-iliac (S2AI) trajectory; (2) fixation in T10-S1, PFFI bilaterally in S2AI trajectory, triangular implants bilaterally above the PFFI in a sacro-alar-iliac trajectory (PFFI-IFSAI); and (3) fixation in T10-S1, PFFI bilaterally in S2AI trajectory, PFFI in sacro-alar-iliac trajectory stacked cephalad to those in S2AI position (2-PFFI). Models were loaded with pure moments of 7.5 Nm in flexion-extension, lateral bending, and axial rotation. Outputs were compared against 2 baseline models: (1) pedicle screws and rods in T10-S1 (PED), and (2) pedicle screws and rods in T10-S1, and S2AI screws.

Results: PFFI and S2AI resulted in similar L5-S1 motion; adding another PFFI per side (2-PFFI) further reduced this motion. Sacroiliac joint (SIJ) motion was also similar between PFFI and S2AI; PFFI-IFSAI and 2-PFFI demonstrated a further reduction in SIJ motion. Additionally, PFFI reduced max stresses on S1 pedicle screws and on implants in the S2AI position.

Conclusion: The study shows that supplementing a long construct with PFFI increases the stability of the L5-S1 and SIJ and reduces stresses on the S1 pedicle screws and implants in the S2AI position.

Clinical relevance: The findings suggest a reduced risk of pseudarthrosis at L5-S1 and screw breakage. Clinical studies may be performed to demonstrate applicability to patient outcomes.

Level of evidence: Not applicable (basic science study).

Keywords: S2 alar-iliac screws; porous fusion/fixation implants; sacropelvic fixation; triangular implants.

Author Information

  • Panico M, Villa T - IRCCS Istituto Ortopedico Galeazzi, Milan, Italy; Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Milan, Italy.
  • Chande RD, Lindsey DP, Yerby SA - SI-BONE, Inc., Santa Clara, CA, USA.
  • Mesiwala A - DISC Sports and Spine Center, Newport Beach, CA, USA.
  • Polly DW - Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota, USA.
  • Brayda-Burno M - IRCCS Istituto Ortopedico Galeazzi, Milan, Italy.
  • Galbusera F - Spine Center, Schulthess Clinic, Zurich, Switzerland.

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