Individualized 3D printed model-assisted posterior screw fixation for the treatment of craniovertebral junction abnormality: a retrospective study.

OBJECTIVE This study was undertaken to evaluate the feasibility and efficacy of individualized 3D printed model-assisted posterior internal fixation in treating craniovertebral junction (CVJ) abnormalities. METHODS Forty-four patients (19 males and 25 females; mean age 36.5 ± 9.2 years, range 11-62 years; symptom duration 1 month-15 years) with a CVJ abnormality who were admitted to the authors' institution between April 2010 and April 2015 were retrospectively studied. The individualized 3D printed model of the CVJ was produced based on the individual CT data by use of 3D printing technology. The posterior internal fixation was simulated on the model to obtain data for individual patients, which were then used for intraoperative assistance. One-stage posterior decompression combined with internal fixation was performed. The results were evaluated using the Japanese Orthopaedic Association (JOA) scale, atlanto-dens interval (ADI), and cervicomedullary angle (CMA). The patients underwent follow-up and outcomes were evaluated using CT, MRI, and the JOA scale score. The comparison between preoperative and postoperative JOA scale scores was done using a paired t-test. RESULTS Thirty-eight individualized 3D printed models were successfully built. The 38 patients underwent successful posterior internal fixation performed with the assistance of 3D printed models. In the 6 patients without an individualized printed model (i.e., the patients who underwent surgery before 3D printed modeling was available at the authors' institution), the pedicle screw was inserted incorrectly into the transverse foramen in 2 patients and inserted incorrectly into the vertebral canal in 1 patient. All patients were observed for a mean of 26 months (range 3-52 months). The postoperative JOA scale scores for all patients significantly improved from the preoperative scores. Among the 41 patients treated with atlantoaxial distraction reduction, postoperative MRI and CT showed complete reduction in 31 patients and incomplete reduction in 10 patients (reduction rate > 50%). The postoperative ADI significantly decreased, and the CMA significantly increased. CONCLUSIONS Individualized 3D printed model-assisted posterior internal fixation seems feasible and effective in optimizing the treatment of CVJ abnormalities. In addition, it offers many advantages, including preoperative simulation, intraoperatve guidance, and intraoperative error minimization.