[The feasibility of digital guidance drill template assisted expansive open-door laminoplasty]

Objective: To explore The feasibility of digital guidance drill templates assisted expansive open-door laminoplasty. Methods: Ten specimens of normal adult cervical spine (C_3-7) were selected, including six males and four females. The specimens aged 42-67 years, with an average age of (43.6±4.2) years. After CT scanning, the date was imported into Mimics software in DICOM format. 3D models were reconstructed and the position and depth of troughs on the open side and hinge side were selected for expansive open-door laminoplasty. Drill templates were designed and exported in STL, manufactured by 3D printing finally. Then drill templates were attached to the posterior part of cervical lamina and spinous process. Under guidance of templates, troughs of both sides were conducted by using a high-speed drill. Then the lamina is elevated and instrumentations were implanted. Postoperative CT scanning was conducted to record the fracture of trough on the hinge side. 3D reconstruction was performed again to compare the position and depth between theory and actual trough on both sides by paired t test. Results: A total of 50 drill templates were designed and manufactured. There was no occurrence of hinge fracture after operation. In C_3-7, the distance range between the theory position of troughs on the open side and the midline was 11.8-14.4 mm, while in actual it was 11.4-14.0 mm. The distance range between the theory position of troughs on the hinge side and the midline was 11.6-14.3 mm; in actual, it was 10.9-14.0 mm. The theory depth range of trough on the hinge side was 3.0-3.8 mm, while the actual depth was 3.1-3.8 mm. According to the statistical analysis, the difference in the position of trough on the open side, the position of trough on the hinge side and the depth of trough on the hinge side between theory and actual were not statistically significant (all P>0.05). Conclusion: Digital guided template assisted open-door laminoplasty is a feasible technique, which can improve the accuracy and safety of the position and depth of the trough, and has clinical application value.