Abstract
Background
The incidence of rod fracture after corrective surgery for adult spinal deformity
(ASD) is high. Although many reports have investigated the effects of rod bending
considering postoperative body motion, and countermeasures, there are no reports investigating
the effects during intraoperative correction. The purpose of this study was to investigate
the effect of ASD correction on rods by using finite element analysis (FEA) based
on the rod shape changes before and after spinal corrective fusion.
Methods
Five ASD patients (mean age 73 years, all female) who underwent thoracic to pelvic
fusion were included in this study. A 3D rod model was created using computer-aided
design software from digital images of the intraoperatively bended rod and intraoperative
X-ray images after corrective fusion. The 3D model of the bent rod was meshed by dividing
each of the screw head intervals into 20 sections and cross-section of the rod into
48 sections. Two surgical fusion methods of stepwise fixation as the cantilever method
and parallel fixation as the translational method were simulated to evaluate stress
and bending moments on the rods during intraoperative correction.
Results
The stresses on the rods were 1500, 970, 930, 744, and 606 MPa in the five cases for
stepwise fixation and 990, 660, 490, 508, and 437 MPa for parallel fixation, respectively,
with parallel fixation having lower stresses in all cases. In all cases, maximum stress
was found around the apex of the lumbar lordosis and near L5/S1. The bending moment
was high around L2-4 in most cases.
Conclusions
The external forces of intraoperative correction had the greatest effect on the lower
lumbar region, especially around the apex of the lumbar lordosis.
Keywords
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Article info
Publication history
Published online: March 16, 2023
Accepted:
March 5,
2023
Received in revised form:
March 2,
2023
Received:
December 16,
2022
Publication stage
In Press Corrected ProofFootnotes
☆Study design: case series, finite element study.
Identification
Copyright
© 2023 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.
