Biomechanical Characteristics of Internal Fixation Methods for Treating Thoracolumbar Burst Fractures / 医用生物力学

Objective To analyze the biomechanical characteristics of 3 different posterior internal fixation methods for treating thoracolumbar burst fracture by three-dimensional finite element (FE) method. Methods The FE fixation models of normal thoracolumbar, short-segment posterior fixation (SSPF), short-segment posterior fixation with intermediate screws at fractured level (SSPFI) and long-segment posterior fixation (LSPF) were established, respectively. The biomechanical characteristics of L1 centrum and the adjacent intervertebral disc under 6 kinds of motion states (spinal flexion, extension, lateral bending and axial rotation), in normal thoracolumbar model and 3 fixation models were compared by FE analysis. Results L1 centrum equivalent stress distributions in normal thoracolumbar model, SSPF model, SSPFI model, LSPF model were 31.63, 13.41, 110.35, 13.17 MPa, respectively. The maximum equivalent stress of adjacent intervertebral disc in normal thoracolumbar model was 3.84 MPa, which was located in L1-2 intervertebral disc; the maximum equivalent stress of adjacent intervertebral disc in 3 fixation models was 0.41, 0.36, 0.40 MPa, respectively, which was all located in T12-L1 intervertebral disc. Conclusions Fixation in short segment of the fractured vertebrae could lead to an increase of stress in the centrum. The stress of the adjacent intervertebral disc in 3 fixation models was smaller than that in normal spinal model.

Lateral Extracavitary Approach to Thoracic Cord Tumor and Disc Herniation

We treated 9 patients of ventrally or ventrolaterally located thoracic lesions with lateral extracavitary approach, six cases of ventrally located thoracic cord tumor, and three cases of central disc herniation. After operation, the patients' neurological symptoms were effectively improved and there were no signigicant postoperative c omplications. Compared to transthoracic approach, this approach is less invasive and enable simultaneous vertebral reconstruction and posterior spinal fixation. Although relatatively small in number experienced, lateral extracavitry approach is considered to be a alternative method to transthoracic approach for the treatment of ventrally and ventrolaterally located thoracic lesion.