Objective:To investigate the clinical efficacy of 3D printed osteotomy guide plate combined with "Jail" screw technique in the treatment of tibial plateau fractures involving external posterior condylar collapse.Methods:From January 2016 to January 2021, 41 patients (22 males and 19 females) with tibial plateau fractures involving external posterior condylar collapse were treated with 3D printed osteotomy guide plate combined with "Jail" screw technique and followed up. The age was 47.4±11.5 years (range, 22-69 years). According to Schatzker fracture type, 18 cases were type IV, 14 cases were type V and 9 cases were type VI. All fractures were closed, and 12 of them were complicated with lateral meniscus injury, but none of them were complicated with nerve and vascular injury. The time from injury to operation was 7.2±3.4 d (range, 4-17 d). All patients underwent 3D CT scanning and digital modeling before operation. According to the modeling results, a 1∶1 solid size fracture model was made by 3D printing, and the osteotomy guide plate and the "Jail" screw preset guide plate were designed. During the operation, the tibial lateral condyle osteotomy was performed with customized osteotomy guide plate. After reduction, the fixation of the fracture was performed with the preset guide plate using "Jail" screw. Postoperative fracture reduction was evaluated according to Rasmussen score, and knee function was evaluated by Hospital for Special Surgery (HSS) score.Results:All the 41 patients were followed up for 15.2±5.8 months (range, 6-26 months). Immediate postoperative radiographs showed good fracture reduction, and the average healing time was 14.1±1.2 weeks (range, 12-17 weeks). One year after operation, the Rasmussen score of knee joint was 17.4±1.6 points (range, 13-19 points), of which 31 cases were excellent, 8 cases were good, and 2 cases were fair, with an excellent/good rate of 95% (39/41). HSS scores was 87.3±5.6 points (range, 68-95 points), including 30 excellent cases, 10 good cases and 1 fair case, with an excellent/good rate of 98% (40/41). The range of motion of knee joint was 126.8°±3.8°. At the last follow-up, no serious complications such as common peroneal nerve injury, popliteal vascular injury, postoperative infection, or internal fixation failure occurred.Conclusion:3D printed osteotomy guide plate combined with "Jail" nail placement technique is an effective method for tibial plateau fractures involving external posterior condylar collapse, and the postoperative treatment results are satisfactory. The use of customized osteotomy guide plate is more accurate and less damaging. The use of "Jail" screw preset guide plate can ensure more accurate screw placement.