关键词: 胸腰椎, 骨折, 椎弓根钉, 内固定, 徒手置钉, 3D打印, 椎体前缘高度, Cobb角

Abstract: BACKGROUND: Percutaneous pedicle screw internal fixation was a common surgical method to reconstruct the spine and restore local stability. The accuracy and safety of pedicle screw placement directly affect the postoperative mobility and quality of life of patients. Three-dimensional (3D) printing technology can reconstruct the local structure model of the spine of patients before surgery based on accurate imaging data, simulate screw placement operation, accurately measure the insertion point, direction, and angle, and then provide the data support for intraoperative operation. Theoretically, 3D printing assisted nail placement had a higher accuracy and better prognosis than freehand nail placement, but that needed a large number of clinical data to confirm.
OBJECTIVE: To investigate the clinical characteristics and influence on the postoperative stability of thoracolumbar fractures treated with 3D printing-assisted pedicle screw fixation and freehand pedicle screw fixation.
METHODS: Patients with thoracolumbar fracture (T10-L3) and treated by the percutaneous pedicle screw internal fixation surgery were selected in the Affiliated Hospital of Guizhou Medical University from October 2016 to July 2018 as the research objects. According to the surgical plan, there were 30 patients with unarmed nailing by perspective guided method, and 30 patients with nailing by 3D printing aided. The operation time, blood loss, intraoperative fluoroscopy times, the number of nailing, and nailing accuracy for the first time were compared. The anterior vertebral height ratio, kyphosis Cobb angle, curvature changes, and functional recovery were compared between the two groups during a 1-year follow-up. 
RESULTS AND CONCLUSION: (1) Compared with the freehand group, the amount of intraoperative blood loss and intraoperative fluoroscopy were reduced; the operation time and hospital stay were shortened; and the accuracy and accuracy rate of the first intraoperative nail placement were increased in the 3D printing group, with statistically significant differences (P < 0.05). (2) There was no statistically significant difference between the two groups in visual analogue scale score and postoperative 1 year satisfaction (P > 0.05). (3) Compared with the freehand group, the correction degree of sagittal curvature of the fixed segment increased after surgery in the 3D printing group. (4) The Oswestry disability index of the 3D printing group decreased at 7 days, 3 and 12 months after the operation compared with the freehand group, and the difference was statistically significant (P < 0.05). (5) In terms of vertebral stability, the anterior vertebral height ratios of the two groups showed a downward trend at 7 days, 3 and 12 months after surgery, while the Cobb angle showed an increasing trend. However, there was no significant difference between the two groups (P > 0.05). (6) It is indicated that 3D printing assisted pedicle screw placement relies on advanced reconstruction technology to realize simulated surgery, and the data related to pedicle screw placement formed on this basis can guarantee the accuracy of one-time pedicle placement in real surgery, so as to maximize the short-term recovery and mid-term stability of spinal function.

Key words: thoracolumbar spine, fracture, pedicle screw, internal fixation, freehand nail placement, 3D printing, anterior vertebral height, Cobb angle