To explore a 3D printing model of fracture restoration which can be used in preoperative planning and design for distal tibiofibular fractures.

A retrospective analysis was performed of the 35 patients with distal tibiofibular fracture who had been treated from October 2015 to September 2016 at our department. Bilateral tibiofibular CT scan was performed in all the cases to obtain Dicom data. Using Mimics 15.0 software, cross sections were created at 5 cm, 10 cm and 15 cm above the knee joint at the bilateral upper tibiae and marked as PT5, PT10 and PT15. The long and short axles on the left and right sides were measured and compared (LL vs. RL; LS vs. RS). After the STL files for 3D models were generated using Mimics 15.0 software, a real-sized 3D model of the distal tibiofibular fracture and a mirror model of the contralateral tibiofibula were printed. The fracture lines were drawn and preoperative manoeuvre was performed on the mirror 3D printed model. The real operation used the implants preoperatively designed; the actual screw lengths were measured and compared radiographically with those designed in the preoperative manoeuvre.

All the data were collected of the long and short axles on the 3 cross-sections (PT5, PT10 and PT15) of the left and right sides of the proximal tibia. The samples were paired into 6 groups. The correlation coefficients of paired samples were greater than 0.95, showing an ex-tremely strong correlation. The differences between the left and right sides showed no statistically significance in paired samples of LR-RL and LS-RS groups on PT5, PT10 and PT15 cross-sections (P >0.05). All the 35 cases received surgical operation. The postoperative X-ray review showed fine agreement between actual surgery and preoperative design in terms of screw length and accuracy. The deviations were in an allowable range, leading to satisfactory internal fixation.

A mirror 3D model of the healthy side is of clinical value to some extent because it can serve as one for an anatomically reduced fracture which can be used for preoperative manoeuvre and preparation of implants. The contrasts between the long and short axles on the 3 cross-sections may simplify and facilitate comparisons of bilateral similarity, avoid the blindness in direct application of the health side mirror model for preoperative planning.

Ankle joint; Fractures fixation, internal; 3D printing technology