The accuracy of a method for printing three-dimensional spinal models

Abstract

Background: To study the morphology of the human spine and new spinal fixation methods, scientists require cadaveric specimens, which are dependent on donation. However, in most countries, the number of people willing to donate their body is low. A 3D printed model could be an alternative method for morphology research, but the accuracy of the morphology of a 3D printed model has not been determined.

Methods: Forty-five computed tomography (CT) scans of cervical, thoracic and lumbar spines were obtained, and 44 parameters of the cervical spine, 120 parameters of the thoracic spine, and 50 parameters of the lumbar spine were measured. The CT scan data in DICOM format were imported into Mimics software v10.01 for 3D reconstruction, and the data were saved in .STL format and imported to Cura software. After a 3D digital model was formed, it was saved in Gcode format and exported to a 3D printer for printing. After the 3D printed models were obtained, the above-referenced parameters were measured again.

Results: Paired t-tests were used to determine the significance, set to P<0.05, of all parameter data from the radiographic images and 3D printed models. Furthermore, 88.6% of all parameters of the cervical spine, 90% of all parameters of the thoracic spine, and 94% of all parameters of the lumbar spine had Intraclass Correlation Coefficient (ICC) values >0.800. The other ICC values were <0.800 and >0.600; none were <0.600.

Conclusion: In this study, we provide a protocol for printing accurate 3D spinal models for surgeons and researchers. The resulting 3D printed model is inexpensive and easily obtained for spinal fixation research.

Fig 1. Schematic diagram showing the method of measurement for C1 (Atlas).

WD is the abbreviation of Width diameter; APD is Anteroposterior diameter; WVC is Width of vertebral canal; APDVC is Anteroposterior diameter of vertebral canal; WAT is Width of anterior tubercle; HAT is Height of anterior tubercle; WPT is Width of posterior tubercle; and HPT is Height of posterior tubercle.

Fig 2. Schematic diagram showing the method of measurement for C2 (Axis).

MAPD is the abbreviation of Max anteroposterior diameter; MLRD is Max left-right diameter; APDVD is Anteroposterior diameter of vertebral body; WVC is Width of vertebral canal; APDVC is Anteroposterior diameter of vertebral canal; and FHA is Frontal height of axis (including the odontoid process).

Fig 3. Schematic diagram showing the method for measurement ofC3-L5.

WVD is the abbreviation of Width of vertebral body; APDVD is Anteroposterior diameter of vertebral body; LHVD is Left height of vertebral body; RHVD is Right height of vertebral body; WVC is Width of vertebral canal; APDVC is Anteroposterior diameter of vertebral canal; WRP is Width of right pedicle; HRP is Height of right pedicle; WLP is Width of left pedicle; HLP is Height of left pedicle.