Are computer numerical control (CNC)-manufactured patient-specific metal templates available for posterior thoracic pedicle screw insertion? Feasibility and accuracy evaluation

  • Xiangxue Kong
  • Lei Tang
  • Qiang Ye
  • Wenhua Huang
  • Jianyi Li
Original Article

Abstract

Purpose

Accurate and safe posterior thoracic pedicle insertion (PTPI) remains a challenge. Patient-specific drill templates (PDTs) created by rapid prototyping (RP) can assist in posterior thoracic pedicle insertion, but pose biocompatibility risks. The aims of this study were to develop alternative PDTs with computer numerical control (CNC) and assess their feasibility and accuracy in assisting PTPI.

Methods

Preoperative CT images of 31 cadaveric thoracic vertebras were obtained and then the optimal pedicle screw trajectories were planned. The PDTs with optimal screw trajectories were randomly assigned to be designed and manufactured by CNC or RP in each vertebra. With the guide of the CNC- or RP-manufactured PDTs, the appropriate screws were inserted into the pedicles. Postoperative CT scans were performed to analyze any deviations at entry point and midpoint of the pedicles.

Results

The CNC group was found to be significant manufacture-time-shortening, and cost-decreasing, when compared with the RP group (P < 0.01). The PDTs fitted the vertebral laminates well while all screws were being inserted into the pedicles. There were no significant differences in absolute deviations at entry point and midpoint of the pedicle on either axial or sagittal planes (P > 0.05). The screw positions were grade 0 in 90.3% and grade 1 in 9.7% of the cases in the CNC group and grade 0 in 93.5% and grade 1 in 6.5% of the cases in the RP group (P = 0.641).

Conclusion

CNC-manufactured PDTs are viable for assisting in PTPI with good feasibility and accuracy.

Keywords

Patient-specific drill templates Computer numerical control Rapid prototyping Thoracic spine Pedicle 

Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • Xiangxue Kong
    • 1
  • Lei Tang
    • 1
  • Qiang Ye
    • 2
  • Wenhua Huang
    • 1
  • Jianyi Li
    • 1
    • 3
  1. 1.Department of Anatomy, Guangdong Provincial Key Laboratory of Medical Biomechanics, School of Basic Medical SciencesSouthern Medical UniversityGuangzhouChina
  2. 2.Department of RadiologyThe Third Affiliated Hospital, Southern Medical UniversityGuangzhouChina
  3. 3.Department of Orthopedics, Nanhai HospitalSouthern Medical UniversityFoshanChina

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