Abstract: BACKGROUND: With the application and development of 3D printing technology in medicine, orthopedic internal fixation surgery has become precise and individualized. The equal-scale fracture model obtained by 3D printing technology was simulated and planned before surgery, realizing the leap from traditional 2D images to more vivid and detailed three-dimensional objects. It allows the surgeon to understand the fracture type in advance and rehearse the reduction sequence, so as to realize the individualized implementation of fracture surgery, optimize the surgical process, bring better postoperative recovery and less surgical complications.  
OBJECTIVE: To compare clinical efficacy of three 3D printed models combined with computerized virtual repositioning technology to assist incision reduction bone plate internal fixation and traditional incision reduction bone plate internal fixation in the treatment of Robinson II B2 clavicle fracture. 
METHODS: Eighty patients with Robinson II B2 clavicle fracture were randomly divided into trial group (n=40) and control group (n=40). In the trial group, three kinds of 3D printing models (affected clavicle fracture model, computer simulation clavicle fracture reduction model, clavicle mirror model of healthy side) combined with computer virtual reduction technology were used for preoperative in vitro surgery rehearsal. Finally, 3D printing was used for clavicle mirror model of healthy side to advance bending and select bone plates for internal fixation. In the control group, open reduction plate internal fixation was applied. The time from admission to surgery, intraoperative blood loss, operation time, frequency of fluoroscopy, number of bends of the bone plate, fracture healing time, complications, and visual analog scale score and Constant score before and after surgery were compared between the two groups. 
RESULTS AND CONCLUSION: The time from admission to operation in the trial group was greater than that in the control group (P < 0.05). Operation time, intraoperative fluoroscopy frequency and bending times of the bone plate in the trial group were lower than those in the control group (P < 0.05). The trial group had faster fracture healing and fewer complications (P < 0.05). There was no significant difference in intraoperative blood loss between the two groups (P > 0.05). Constant score of the two groups had an increasing trend with time (F=613.50, P < 0.001), but the difference between the groups was not statistically significant (F=0.08, P=0.78), and there was no interaction between the measurement times and the group assignment (F=0.27, P=0.66). The visual analog scale score decreased with time (F=1 149.55, P < 0.001), but there was no significant difference between groups (F=0.02, P=0.88), and there was no interaction between the number of measurements and the group assignment (F=1.02, P=0.36). The results show that the use of 3D printed model combined with computer virtual reduction technology for preoperative rehearsal can shorten the operation time, reduce the number of intraoperative fluoroscopy frequency and the times of bone plate bending, and have the advantages of faster fracture healing, fewer complications, and similar functional recovery to the traditional incision reduction bone plate internal fixation.

Key words: 3D printing, Robinson II B2, clavicle fracture, bone plate internal fixation, CT three-dimensional reconstruction, preoperative rehearsal, virtual reset