Individualized transoral anterior surgery for complex craniocervical junction disorder with assistance of 3D printing technology

Abstract

Objective To evaluate the value of 3D printing technology in transoral anterior surgery for complex craniocervical junction disorder. Methods From December 2009 to December 2013, 48 cases of atlantoaxial dislocation associated with complex craniocervical malformation were operated with the assistance of 3D printing technology. There were 19 males and 29 females, with mean 35 years of age (range, 6 to 59 years). Preoperative complications included 28 cases of atlas assimilation, 19 cases of os odontoideum, 17 cases of C2-3 fusion, 1 case of C2-5 fusion, 1 case of C1 posterior arch disconnection, and 1 case of C1 posterior arch aplasia. All cases had symptoms of spinal compression such as numbness and weakness of the extremity, standing or walking unsteady, etc. Preopoerative cervical MRI examinations showed the enlargement of anterior atlas-dens interval (ADI) or atlantoaxial dislocation. All cases' CT data in Dicom form were input into the Simpleware software to reconstruct 3D image, and then the image in STL form was imported to the 3D printer to make a fast prototyping model for the operation with same size as the cases' cervical spine. Based on above works, all cases underwent transoral anterior reduction plate (TARP) fixation in the craniocervical junction zone, including combined anterior-posterior surgery in 1 case. ADI was measured to evaluate the reduction of atlantoaxial dislocation, cervical-medullary angle (CMA) was measured to evaluate the improvement of compression on the medulla, and Japanese Orthopedic Association (JOA) scoring system was used to evaluate the improvement of spinal function. Results All cases went through successful surgery. Mean operation time was (145±45)min and mean blood loss was (53±15)ml. A total of 96 atlas lateral mass screws, 62 reverse axis pedicle screws and 36 axis vertebral body screws, 1 posterior axis pedicle screw and 1 axis translaminar screw were used. Postoperative CT scans showed all screw trajectories were good except that 4 reverse axis pedicle screws violated into the vertebrae artery foramen due to large outward inclination angle. No neurologic defect was found in all cases. Excellent rate of screw placement was 98%. Postoperative CT reconstruction images showed significant atlantoaxial reduction. ADI improved from (8.7±4.9)mm preoperatively to (2.7±1.9)mm postoperatively (P<0.05). CMA changed from preoperative (123±17)° to postoperative (159±18)° (P<0.05). All cases had obvious improvement of spinal compression symptoms. JOA scores improved from (9.5±1.7)points preoperatively to (15.7±0.9)points at 3 months postoperatively (P<0.05). All cases achieved bone union at a follow-up of 10-58 months. Conclusion 3D printing technology is helpful to the operation plan and manipulation for atlantoaxial dislocation associated with complex craniocervical deformities, which may improve the accuracy and safety during the procedure. Key words: Atlanto-axial joint; Dislocations; Imaging, three-dimensional; Computer-assisted design