Accuracy and Cost Comparison of 3D-Printed Guides in Complex Spinal Deformity Correction: Direct vs. Indirect Design

Wei Yang¹Wei Guo¹Wenjun Wu²Ma Rong¹Zemin Wang¹Honglai Zhang¹Wanzhong Yang¹Zhaohui Ge^2*

• ¹School of Clinical Medicine, Ningxia Medical University, Yinchuan, China
• ²General Hospital of Ningxia Medical University, Yinchuan, China

To compare the effectiveness, accuracy, and cost of various 3D-printed guiding templates for pedicle screw placement and osteotomy in the treatment of complex and severe spinal deformities.Methods: CT scan data (DICOM format) from 10 patients with complex and severe spinal deformities were selected. Full spinal reconstruction was performed using Mimics, CAD, and E-3D software. Two different types of screw placement and osteotomy guides were designed: direct (using a larger aperture design to allow direct screw placement) and indirect (using a K-wire or 2.5mm drill bit to preset the screw path before screw placement). Screw placement and osteotomy were simulated using 3D-printed spinal models and guides. Post-operative CT scans were performed on the models and compared with pre-operative designs to evaluate the accuracy, efficiency, cost, and clinical practicality of different guides during screw placement and osteotomy.Results: This study included 10 patients with complex spinal deformities (5 males and 5 females, with an average age of 37 years), covering 5 diagnostic types such as neurofibromatosis and adult idiopathic spinal deformity. Nine cases of Vertebral Column Resection (VCR) and one case of pedicle subtraction osteotomy (PSO) were performed. Experimental data showed no statistically significant differences between the direct and indirect guide groups in terms of pedicle screw placement accuracy (95.97% vs 94.63%), coronal osteotomy accuracy (ROED 96.69% vs 98.68%), and sagittal osteotomy accuracy (94.24% vs 96.86%) (P>0.05). However, the digital preparation efficiency of the direct guide group was significantly lower than that of the indirect group, with a 33.2% increase in single guide design time and a 44.6% increase in printing time (P<0.001), resulting in a 35.8% increase in total design time (P=0.026). There were no significant differences between the two groups in screw placement time (4.24 vs 4.79 minutes), osteotomy time (37.15 vs 36.56 minutes), and material cost ($268.25 each). Conclusion: Both direct and indirect 3D-printed guides can optimize screw implantation and complex osteotomy procedures, improving the accuracy of pedicle screw placement and osteotomy. However, the direct guide group has clinical limitations such as extended design cycles, increased printing time, and expanded surgical field exposure.