Abstract:[Objective] To introduce the surgical techniques and preliminary clinical results of 3D printing assisted open reduction andinternal fixation of severe olecranon fractures. [Methods] Preoperative CT data in DICOM format was used to manufacture 1:1 fracture 3Dmodel for simulated reduction, and the plate type and placement positions of the implants were determined. The spatial information of thekey screw hole was obtained by referring to anatomical markers and the edge distance of fracture fragment, and the spatial information wasre-imported into the software. Combining the spatial information of the key screw hole in the major bone pieces in the software, mimic frac-ture reduction and fixation were conducted to restore to the initial position. Intraoperatively, fracture reduction and internal fixation wereperformed based on the 3D printing templates. [Results] All patients had operation performed successfully without vascular and nerve inju-ry complications. At the latest follow-up lasted for more than 12 months, all the patients got fractures healed well, one of them was of ecto-pic ossification, and 2 cases of osteoarthritis. However, 12 months after operation, the affected side proved inferior to the healthy side interms of elbow flexion [(126.1±10.0)° vs (133.2±12.1)°, P=0.023], extesion [(14.2±6.2)° vs (9.1±5.0)°, P＜0.001], and range of motion of theelbow [(111.1±11.2)° vs (124.0±14.1)°, P=0.001]. The Mayo elbow performance score was of (86.0±14.2), while the excellent and good rateof clinical outcome rate was of 73.1%. [Conclusion] 3D printing assisted open reduction and internal fixation for severe olecranon fracturedo simplify the operation, and improve the accuracy and efficiency of fracture reduction and fixation.