Feasibility of three-dimensional printing composite template for lumbar posterior cortical bone screw

Li Zhi-duo; Yuan Feng; Sheng Xiao-lei; Lu Hai-tao; Jiang Wei; Li Wei

doi:10.3969/j.issn.2095-4344.2016.48.013

Abstract：BACKGROUND:Cortical bone trajectory is a new lumbar posterior internal fixation technology, whose trajectory is different from traditional internal fixation technology. Cortical bone trajectory led to high failure rate lacking of experience for insertion. However, the three-dimensional template improves its safety and accuracy. <br> OBJECTIVE:To validate the security and accuracy of lumbar vertebral cortical bone screw placement under the assistance of three-dimensional printing oriented template, and compare to the group with free hand insertion. <br> METHODS:Six normal lumbar spine specimens were selected and randomly divided into groups A, B and C (n=2). Specimens in group A underwent free hand screw placement;group B underwent screw placement by the crista lambdoidalis composite guide;while group C underwent screw placement by the spinous process composite guide. Al patients received CT scan. After data were processed using Mimics software for three-dimensional model reconstruction, computer-assisted design of optimum trajactory for lumbar vertebral cortical bone screw placement was worked out and made into a dril and screw template, where the surface was created as the inverse of lumbar posterior surface respectively. The dril template and lumbar model were materialized in a rapid prototyping machine. X-ray and CT scan were conducted to identify the screw position and direction, as wel as pedicle cortical rupture. According to Grade grading, success rates and acceptable rates in groups A, B and C were evaluated and compared. <br> RESULTS AND CONCLUSION:(1) Among the three groups (2 specimens), 20 posterior cortical bone screws were implanted, showing a success rate of 70%(14/20) and acceptable rate of 80%(16/20) in the group A;a success rate of 70%(14/20) and acceptable rate of 95%(19/20) in the group B;a success rate of 95%(19/20) and acceptable rate of 100%(20/20) in the group C. (2) The success rate was significantly higher in the group C than in the groups A and B (P<0.05). The acceptable rate was significantly higher in the group C than in the group A (P<0.05). (3) These results verified that the group of vertebral lamina and spinous process composite template has a high matching relation which improves the safety and accuracy. It can theoretical y reduce the risk of nerve and blood vessel injury. Simultaneously, the construction of crista lambdoidalis is not fit for the surface of template, which cannot completely match with the specimen.