INTRODUCTION METHODS CASE SERIES DISCUSSION The utility of 3D printing for surgical planning and patient-specific implant design for complex spinal pathologies: Initial experience. Ralph Mobbs, Marc Coughlin, Robert Thompson, Chet Sutterlin, Paul D’Urso, Kevin Phan 1UNSW, Kensington NSW, Australia. 2NeuroSpine Surgery Research Group, Randwick NSW, Australia. 3Prince of Wales Public & Private Hospitals, Randwick NSW, Australia, Anatomics P/L Melbourne, ProCRO P/L, Australia INTRODUCTION Case 3. C1/2 Spondylosis. 65/F. Neck pain and occipital neuralgia managed with 3D printed C1/C2 posterior fixation device including pre-planned trans-articular screw trajectory and C1 arch fixation. 12 months postop. Solid fusion with reduction of occipital neuralgia. There has been a rapid growth of interest in the use and potential applications of 3D printing for the assistance of surgical planning & development of personalized prostheses. There have been few reports on the use of 3D printing used in complex spinal surgery. METHODS The authors report 4 cases in which 3D printing was used for surgical planning and for custom-designed, patient specific, titanium prosthesis. CASE SERIES Case 1. C2 Chordoma. 63/M. Chordoma managed with surgical resection and posterior / anterior fixation with 3D printed prosthesis for Clivus - C3 fixation. 20 months postop. Disease free. Minimal neck pain. Case 4. T9 Primary Bone Tumour. 15/F. Thoracic pain and progressive deformity. Extensive resection managed with vertebral replacement device with custom pedicle screw holes to assist with implant application and fixation to posterior construct. 9 months postop with restoration of sagittal alignment and disease free. Case 2. L4/5 Congenital deformity. 52/F. Low Back Pain and sciatica with congenital L4/5 deformity managed with 3D printed ALIF device, with anterior / posterior fixation. 18 months postop. Reduction in pain scores. DISCUSSION Treatment of complex spinal pathologies such as primary spinal tumour and deformity requires meticulous technique and considerable pre-planning. In all presented cases, the custom designed and built implants were easily slotted into position, which facilitated the surgery and shortened the procedure operation time, avoiding further complex reconstruction and operative time.