Anterior single segment interbody fixation in treatment of Denis B type thoracolumbar fracture with different burst degrees: a biomechanical study

Objective To investigate the biomechanical stability of anterior single segment interbody fixation in the treatment of Denis B type thoracolumbar fracture with different burst degrees, and to provide a biomechanical basis for the wide-spread clinical use of single-segment interbody fixation for the treatment of Denis type B fracture. Methods Six fresh human cadaver spine specimens (T11-L3) were included. The fracture models of L1 Denis B type with different burst degrees was established by corpectomy. According to the degrees of injury, the models were divided into 4 groups (n=6 each) , followed by group A (normal group) : no fracture; group B (mild group) : vertebral burst degree 1/2 single segment fixation; and group D (severe group) : completely broken vertebral body with double segment fixation. The flexion and extension, right/left lateral bending and axial rotation range of motion (ROM) were determined by the three-dimensional spinal motion measuring instrument loading with 8.0 Nm torque. Results The flexion and extension, right/left lateral bending and axial rotation ROM somehow increased in group C compared with those in group B, and there were no statistically significant differences (P>0.05) . The flexion and extension, right/left lateral bending and axial rotation ROM in groups B and C were statistically significant different compared with those in group A (P 0.05) . Conclusion The anterior single segment interbody fixation may provide effective initial biomechanical stability for vertebral burst degree >1/2 in Denis B type thoracolumbar fracture. Its stability of flexion and extension, right/left lateral bending and axial rotation ROM is positively correlated with the degrees of burst. When the Denis B type thoracolumbar fracture with vertebral burst degree >1/2 accommodate screws, the anterior single segment interbody fixation can be used in the clinical settings. Key words: Spinal fracture; Thoracic vertebrae; Lumbar vertebrae; Anterior decompression; Spinal biomechanics