BACKGROUND:Calcium sulfate bone substitute material has a good safety and biocompatibility, and possesses good strength after implantation to restore thoracolumbar mechanical strength and reduce vertebral height loss, and moreover, it may gradual y be degraded and absorbed. OBJECTIVE:To explore the influence of posterior pedicle screw fixation combined with calcium sulfate bone substitute material on the recovery of vertebral height after thoracolumbar vertebral compression fractures. METHODS:Forty-two patients with thoracolumbar vertebral compression fractures (T12-L3) were enrol ed to receive posterior pedicle screw fixation combined with calcium sulfate bone substitute, including 27 males and 15 females, aged 21-57 years. Al patients were fol owed-up for 12 months, and then anterior vertebral height, kyphosis Cobb angle, Oswestry disability index score and visual analog scale score before and after treatment were determined and compared. RESULTS AND CONCLUSION:At the end of fol ow-up, no local complications, no coagulation, no immune response and no screw breakage occurred;the anterior vertebral height, kyphosis Cobb angle, Oswestry disability index score and visual analog scale score were significantly improved (P<0.05). These findings indicate that the posterior pedicle screw fixation combined with calcium sulfate bone substitute can restore the vertebral height and promote functional recovery of patients with thoracolumbar vertebral compression fractures.

BACKGROUND:Vertebral compression fractures are the most common vertebral fractures in the elderly patients with osteoporosis, and the correlation between the compression of anterior border of vertebral body and adjacent vertebral refractures is not clear.
OBJECTIVE:To establish a model of different compression of T12vertebral body with finite element method, and analyze the relationship between the compression of T12vertebral body and the stress of adjacent vertebral plate.
METHODS:Based on thoracolumbar CT data of normal adult volunteers, MIMICS/3-matic was imported. Through image segmentation, repair and three-dimensional mesh of accessto thoracic and lumbar T11-L1data, grid assigned material properties was imported to ABAQUS so as to establish ligament, joint and other small features and obtain realistic three-dimensional finite element model. The six degrees of freedom, including anteflexion, posterior extension, left and right flexion, left and right rotation, were loaded, to verify the validity of the normal model. With the frontier of vertebral body compression to 90%, 80%, 70%…10% of the nine states, MISES stressesof the T11andL1segment intervertebral disc endplate were extracted; the relationship curve of compression state and endplate stress was obtained.
RESULTS AND CONCLUSION:(1) The model was highly realistic and could reflect the actual stress state. (2) The stress value of T11vertebral body and L1vertebral body was positively correlated with the compression of T12vertebral body. Increased stress may lead to an increased likelihood of end plate fractures, which increases the risk of fractures in the adjacent vertebralbodies.