Objective:To investigate the application value of computer-assisted preoperative planning (CAPP) in the treatment of AO/OTA type-C distal femoral fractures.Methods:A retrospective analysis was conducted on 150 patients with AO/OTA type-C distal femur fractures from January 2010 to December 2021 using the less invasive stabilization system-distal femur (LISS-DF). Patients were divided into a non-CAPP group and a CAPP group based on whether computer-assisted preoperative planning was utilized. The non-CAPP group included 81 patients (56 males, 25 females) with an age range of 39 to 67 years (mean 54.9±5.8 years), consisting of 22 type-C1 fractures, 35 type-C2 fractures, and 24 type-C3 fractures. The CAPP group comprised 69 patients (50 males, 19 females) with an age range of 45 to 63 years (mean 53.9±4.6 years), including 18 type-C1 fractures, 28 type-C2 fractures, and 23 type-C3 fractures. The study recorded the time of preoperative planning and compared the surgical duration, intraoperative blood loss, times of fluoroscopy intraoperatively, and hospital stay length between the two groups. At the last follow-up, knee function was evaluated using the Hospital for Special Surgery (HSS) knee score and pain was assessed using the visual analogue scale (VAS).Results:The preoperative planning time of CAPP was 22.5±3.4 min (range, 17-31 min). There were statistically significant differences between non-CAPP group and CAPP group in terms of surgical duration (non-CAPP, 110.9±7.7 min; CAPP, 94.4±6.3 min), intraoperative blood loss (non-CAPP, 299.3±34.2 ml; CAPP, 224.1±22.0 ml), times of fluoroscopy intraoperatively (non-CAPP, 11.3±3.1; CAPP, 6.7±2.2), and hospital stay length (non-CAPP, 12.8±3.2 d; CAPP, 6.4±1.9 d) ( P<0.001). All patients were followed up, with the CAPP group having a follow-up duration of 17.7±3.3 months and the non-CAPP group having 18.1±3.7 months. Both groups of patients achieved clinical healing of fractures. The healing time for fractures in the CAPP group and the non-CAPP group were 13.9±1.1 weeks and 14.0±1.3 weeks, respectively, with no statistically significant difference ( t=0.699, P=0.490). At the last follow-up, the average HSS score and VAS score of the patients in the CAPP group were 86.6±3.4 points and 0.9±0.4 points, which were both better than those of the non-CAPP group 79.2±5.1 points and 1.3±0.5 points ( P<0.001). No patients in either group experienced complications related to delayed fracture healing, nonunion, or internal fixation failure. Conclusion:When using LISS -DF steel plate to treat complex distal femoral fractures, CAPP can assist the operator in efficiently and accurately completing preoperative design. Compared with traditional preoperative planning, it can reduce surgical time, surgical trauma, and achieve more satisfactory postoperative outcomes.