J Korean Soc Spine Surg.  2006 Sep;13(3):170-176. 10.4184/jkss.2006.13.3.170.

Finite Element Model of A-P Instrimentation in Thoracolumbar Burst Fracture

Affiliations
  • 1Department of Orthoapedic Surgery, Guri Hospital, Hanyang University College of Medicine, Korea.
  • 2School of Advanced Technology, Kyung Hee University, Korea. yoonhkim@khu.ac.kr
  • 3East-West Neo Medical Center, Kyung Hee University, Korea.

Abstract

STUDY DESIGN: Finite element models of the thoracolumbar spine with various techniques used in spinal fractures were developed to investigate the effects of fixation techniques on spinal stiffness.
OBJECTIVES
To develop finite element models of the thoracolumbar spine with various fixation techniques to compare their spinal stiffness characteristics. SUMMARY OF LITERATURE REVIEW: Various anterior and posterior instrumentation options have been applied to stabilize unstable burst fractures of the thoracolumbar spines. The biomechanical effects of different instrumentation options on spinal stability are still unknown.
MATERIALS AND METHODS
The 3-D finite element model of the human thoracolumbar spine (T12-L2) was reconstructed from CT images. Various anterior and posterior instrumentation techniques, 1-rod and 2-rod anterior fixations, anterior fixations with posterior fixation, and posterior fixation only, were virtually performed in the developed model with a long cage after corpectomy. Five loading cases, axial compression, flexion, extension, lateral bending, and torsion, were applied up to 1000 N and 10 Nm, respectively. The axial displacement and the rotations of T12 with respect to L2 were measured to analyze the stiffness of the spinal segments.
RESULTS
The posterior fixation technique increased the stiffness of the spine the most. The addition of an anterior rod from 1 to 2 increased the stiffness significantly without posterior fixation, but little effect was found with posterior fixation. Among all fixation techniques, the inter-segmental stiffnesses were similar to those of the intact model in torsion cases. In the other loading cases, the inter-segmental stiffnesses were much greater than those of the intact models.
CONCLUSIONS
Finite element models of the thoracolumbar spine were developed with various fixation methods. The intact models were validated with in-vitro experimental tests. The posterior fixation technique had a more significant effect on spine stability than did anterior fixation. And anteroposterior fixation techniques provided increased spinal stiffness

Keyword

Spinal Fixation; Finite Element Model
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