Research on the application of individual digital navigation templates in scoliosis surgery

ZHANG Yu-peng; SHI Ya-min; WANG Hua-dong; HOU Shu-xun

doi:10.3969/j.issn.2095-252X.2015.03.20

Abstract：Objective To evaluate the effects of individual digital navigation templates used in scoliosis surgery. Methods From September 2013 to September 2014, 11 out of 67 patients of scoliosis were chosen randomly based on a computer-aided design, including 5 males and 6 females. The average age was 12.4 years old ( range:6-17 years ). There were 6 cases of adolescent idiopathic scoliosis ( AIS ) , 3 cases of congenital scoliosis, 1 neuromuscular case and 1 case of Marfan’s syndrome. The mean Cobb’s angle of main curves was 69.6° ( range:38°-84° ). CT scan was performed on each desired vertebra, and a 3-D reconstruction model was generated based on the CT scan data. The optimal screw size and orientation were determined. A reverse template of a single vertebral body was completely matched with the posterior bony structure of the spine. The reverse template was connnected with the screw channel to generate a navigation template. And then a physical model was manufactured using the spine model and the navigation template by a rapid prototyping technique and tested in vitro. The template was sterilized and used intraoperatively to assist the insertion of pedicle screws. After the surgery, the positions of the pedicle screws were evaluated using CT scan. Results It took a mean period of 39.3 h ( range:31-45 h ) to accomplish the preoperative preparation. The templates all iftted well both in vitro and in vivo. No screws were adjusted because of the malposition. The accuracy of simulation of pedicle screws in vitro was 100%. A total of 164 pedicle screws were inserted intraoperatively, with 138 screws ( 84.1%) in grade I, 26 screws ( 15.9%) in grade II but no screws in grade III or IV according to the CT image classiifcation. All the screws were acceptable, and there were no screw-related complications. The mean operation time was 147 min ( range:80-220 min ). The mean blood loss was 575 ml ( range:200-850 ml ). The mean Cobb’s angle of main curves was reduced from 69.6° ( range: 38°-84° ) preoperatively to 15.7° ( range: 6°-31° ) postoperatively. The mean correction rate was 77.4%. Conclusions Individual digital navigation templates can be used to assist the insertion of pedicle screws, which are easy to handle, with high stablity and high accuracy in screw insertion. It is an ideal method to improve the safety of scoliosis surgery.