The stability of long-segment and short-segment fixation for treating severe burst fractures at the thoracolumbar junction in osteoporotic bone: A finite element analysis.

Yueh Wu,Fon-Yih Tsuang,Chia-Hsien Chen,Yi-Cheng Lin,Chang-Jung Chiang,Yi-Jie Kuo,Costin Daniel Untaroiu

doi:10.1371/journal.pone.0211676

Abstract

The majority of compressive vertebral fractures in osteoporotic bone occur at the level of the thoracolumbar junction. Immediate decompression is often required in order to reduce the extent of neurological damage. This study evaluated four fixation methods for decompression in patients with thoracolumbar burst fractures, and presented the most suitable method for osteoporotic patients. A finite element model of a T7–L5 spinal segment was created and subjected to an L1 corpectomy to simulate a serious burst fracture. Five models were tested: a) intact spine; 2) two segment fixation (TSF), 3) up-three segment fixation (UTSF), below-three segment fixation (BTSF), and four segment fixation (FSF). The ROM, stiffness and compression ratio of the fractured vertebra were recorded under various loading conditions. The results of this study showed that the ROM of the FSF model was the lowest, and the ROMs of UTSF and BTSF models were similar but still greater than the TSF model. Decreasing the BMD to simulate osteoporotic bone resulted in a ROM for the four instrumented models that was higher than the normal bone model. Of all models, the FSF model had the highest stiffness at T12-L2 in extension and lateral bending. Similarly, the compression ratio of the FSF model at L1 was also higher than the other instrumented models. In conclusion, FSF fixation is suggested for patients with osteoporotic thoracolumbar burst fractures. For patients with normal bone quality, both UTSF and BTSF fixation provide an acceptable stiffness in extension and lateral bending, as well as a favorable compression ratio at L1.

Highlights

Burst fractures of the thoracolumbar segment in the spine typically occur where the lowest thoracic vertebrae connects to the first lumbar vertebrae
This study showed that long-segment fixation is stiffer than short-segment fixation, with the lower range of motion (ROM) in extension, bending, and torsion being consistent with previous finite element studies [35,36]
There is no single "gold standard" method for treating thoracolumbar burst fractures, as a number of aspects such as the bone quality and severity of the fracture should be considered before deciding on a treatment method

Summary

Introduction

Burst fractures of the thoracolumbar segment in the spine typically occur where the lowest thoracic vertebrae connects to the first lumbar vertebrae. The thoracolumbar segment is the most common site for unstable burst fractures, representing approximately 15% of vertebral injuries [2]. Stabilization of the fracture using an anterior approach can decompress any impinged nerves, while a strut made of an iliac graft can support the collapsed vertebral body. Hitchon et al [3] reported on the outcomes of patients with T11-L2 thoracolumbar burst fractures that underwent decompression using an anterolateral or posterior reconstruction approach. The posterior approach was found to be easier to perform, resulted in less trauma and blood loss, was more cost-effective, demonstrated better recovery of neurological function and had superior canal decompression [4]. Stabilization with posterior pedicle screws is the most common approach today for the repair of thoracolumbar burst fractures [5,6]

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