Abstract
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).
Footnotes
Funding The study was funded by SI-BONE, Inc. and by the Italian Ministry of Health (“Ricerca Corrente”).
Declaration of Conflicting Interests R.D.C. is an employee of and has stock options/stock in SI-BONE, Inc. DPL is an employee of and has stock options/stock in SI-BONE, Inc., and has 3 pending patents and 6 granted patents. A.M. reports as a paid consultant for SI-BONE, Inc. and is a royalties’ bearer. D.W.P. is a paid consultant for SI-BONE, Inc. and is a royalties’ bearer. S.A.Y. is an employee of and has stock options/stock in SI-BONE, Inc., and has 3 pending patents and 6 granted patents. F.G. received funding support for this study from SI-BONE, Inc.
Availability of Data and Material All data are available from the corresponding author upon reasonable request.
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