Utility of a custom screw insertion guide and a full-scale, color-coded 3D plaster model for guiding safe surgical exposure and screw insertion during spine revision surgery

Abstract

Several articles have described the use of screw insertion guides during primary spine surgery; however, the use of such a guide during revision surgeries has not been described. The purpose of this study is to describe the utility of a custom screw insertion (CSI) guide assembled using a novel method and a full-scale, color-coded 3D plaster (FCTP) model for safe and accurate revision surgery. The authors applied the CSI guide and the FCTP model in 3 cases. In the first case, a patient with multiple failed cervical spine surgeries underwent occipitocervicothoracic fusion. After a successful result for this patient, the authors applied the CSI guide in 2 other patients who underwent revision lumbar fusion surgeries to confirm the accuracy and the efficacy of the CSI guides in such cases. The models and guides were fabricated using rapid prototyping technology. The effectiveness of these methods was examined. The FCTP model was designed using CT data. During model assembly, implants inserted during previous surgery were removed virtually, and for the cervical spine, vertebral arteries were colored red for planning. The CSI guide was designed with 5 or 6 arms to fit the bone surface precisely after removing artifacts. Surgery was performed by referring to the FCTP model. Because the actual structure of the bone surface was almost identical to that of the FCTP model, surgical exposure around the complex bone shape proceeded smoothly. The CSI guides were positioned accurately to aid the successful insertion of a pedicle screw into the C-2 vertebra in the case of cervical revision surgery, and 4 pedicle screws for lumbar vertebrae in the 2 other patients. Postoperative CT scans showed that all screw positions closely matched those predicted during the preoperative planning. In conclusion, the FCTP models and the novel CSI guides were effective for safe and accurate revision surgery of the spine.