Experimental study of individualized 3D printing-guided template combined with thoracolumbar pedicle screw placement for the treatment of ankylosing spondylitis

Abstract

To evaluate accuracy and safety of individualized 3D printing guided template for thoracolumbar pedicle screw placement in patients with ankylosing spondylitis. From January 2016 to September 2019, thoracolumbar spine three-dimensional CT data of 8 patients with ankylosing spondylitis were included, Mimics 17.0 and ideaMaker computer software were applied to design thoracolumbar pedicle screw guided template of patients with AS, physical model of all patients (T10-L2)were printed by 3D printer, 2 parts in each patient, and divided into guide-plate-assisted screw group (experimental group) and free-hand nail group (control group). Thoracolumbar pedicle screws of both groups were placed by the same spinal surgeon. The accuracy of pedicle screw placement between two groups were evaluated according to results of postoperative CT, the accuracy of the fixation of thoracolumbar pedicle screw was divided into 4 grades, grade 0 and 1 screws were acceptable nails, grade 2 and 3 screws were unacceptable nails. The diameter and length of pedicle screws, the distance between entry point and posterior median line designed by preoperative 3D printing were compared with actual use in operation. Twenty three blocks of thoracolumbar 3D printing screw of ankylosing spondylitis guided templates were designed and printed in guide-plate-assisted screw group, 46 screws were inserted and 44 screws were accepted. The time of implanting a screw into thoracolumbar pedicle was (4.20±1.15) min, the frequency of X-ray was (5.00±1.25) times and the average adjustment times of screw and Kirschner needle during screw placement was (1.76±1.32) times. In the control group, 46 nails were placed by traditional surgical method and 30 screws were accepted. The time of implanting a screw into thoracolumbar pedicle was (14.67±2.23) min, the frequency of X-ray fluoroscopy was (14.46±2.21) times and the average times of Kirschner needle adjustment was (4.76±3.39) times. The success rates between experimental group and control group were 95.65%(44 / 46) and 56.22%(30 / 46) respectively, and had statistical difference (χ2=13.538, P<0.05). There was no significant difference in diameter, length of pedicle screws and the distance of posterior median line between virtual designed by 3D printing before operation and actual situation in opertaion (P>0.05). The operation time of inserting a single screw, the times of X-ray fluoroscopy, and the average times of adjustment screw and Kirschner needle in experimental group were significant less than those in control group(P<0.01). The personalized guide template assisted the thoracolumbar fixation designed by 3D printing could significantly improve safety, accuracy and efficiency of surgery, especially suitable for thoracolumbar vertebral bodies requiring posterior pedicle screw fixation for fracture or dislocation with AS.