Pre-operative planning and templating with 3-D printed models for complex primary and revision total hip arthroplasty.

Background: Complex primary and revision THR requires comprehensive understanding of abnormal bony anatomy. Evaluation and classification of acetabular bone defects is essential to manage them appropriately. It is difficult to appreciate complex defects using conventional 2-Dimensional radiological modalities. 3D printed models can provide both visual and tactile reproduction of the bony anatomy, with potential for better pre-operative planning and making these complex surgeries more precise and accurate. Materials and methods: Anatomical 3D models of pelvis and femur were made based on CT scans of 27 patients undergoing complex primary THR/Revision THR by FDM (Fusion Deposition Modeling) technology using Flash Forge-Dreamer 3D printer with ABS (plastic) material. Models were used for pre-operative planning and simulation of surgery. Aims of the study were to study the accuracy of 3D models in predicting the implant sizes, accuracy in evaluation of acetabular bone defects and validating the utility of 3 D models through surgeon feedback. Results: The acetabular cup size and placement was accurate in 25 (92.6%) patients. Preoperative acetabular bone defect was accurately estimated in all the patients. There were no neurovascular complications at early and 1-year follow-up in this case series. Model realism and reliability survey response from five surgeons was graded, with average overall usefulness of 3D models of 4.86/5, average model realism was 4.9/5, average usefulness for planning was 4.74/5 and usefulness for teaching was 5/5. Conclusion: 3D models are accurate and help in assessing acetabular bone deficiencies reliably in complex and revision THR. Anatomical models help in surgical planning and simulation, enabling surgeons in predicting the correct implant sizes and importantly placement of acetabular cup and for management of bone defects. The safe trajectory of acetabular screws can be simulated and determined, thereby avoiding penetration into pelvis and neuro-vascular injuries.