Background Traditionally, the technique of modified tension band wires (MTBW) has been the most commonly used surgical procedure. The purpose of this study is to design a precise navigation device that can obtain a standard position of K-wires for (MTBW) and to compare the precise MTBW (P-MTBW) by a navigation device with the conventional MTBW (C-MTBW) by hands in a retrospective study. Methods The device was designed by solidworks2012 software (USA), which could provide a precise guidance for

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... btaining parallel K-wires. Besides, it could set the distance between two K-wires and the level of K-wires below patellar anterior surface. From June 2014 to August 2018, a total of 112 patients were employed in this retrospective study. The patients were divided into P-MTBW group and C-MTBW group according to the surgical technique with or without the precise navigation device. We needed to record and analyze the operation time and the number of fluoroscopy, postoperative internal fixation imaging, knee function and complications. Results There were 54 patients in P-MTBW group and 58 patients in C-MTBW group. There were statistically significant differences (P < 0.001) in the operation time between P-MTBW group (39.5 ± 4.7; range, 32–49 min) and C-MTBW group (53.7 ± 6.8; range, 42–71 min). The number of intraoperative fluoroscopy was significantly less (P < 0.001) in P-MTBW group (4.2 ± 1.4) versus that of C-MTBW group (8.3 ± 2.7). According to Iowa knee score, there was no significant difference (P = 0.268 at 1 year) in function between the two groups. According to our own evaluation criteria for MTBW, anyone in the P-MTBW group was excellent and 26 patients were excellent, 20 patients were good, and 2 patients were fair in the C-MTBW group. Conclusion The navigation device can reduce operation time and intraoperative fluoroscopy frequency. P-MTBW fixation is an accurate and effective surgical procedure for patella fractures.