3D printing of implants for patient-specific acetabular fracture fixation: an experimental study

To test the effect of 3D printed implants, designed according to surgeon's individual plan, on the accuracy of reduction of an acetabular fracture model.

Seven identical standardized plastic bone models of an anterior column/posterior hemi-transverse acetabular fracture were used. A CT of one plastic fracture model was made. Using preoperative planning software, three surgeons independently planned the reduction and fixation procedure and designed implants and drill guides. The designed implants and guides were then 3D printed. Each surgeon first executed his plan using his 3D printed plates and guides on one fracture model and then performed another procedure on an identical model with standard implants and instrumentation. Displacement of the fragments at the weight-bearing fracture lines in the acetabulum was measured after fixation. Linear mixed effect models were used to evaluate the effect of different solutions to the same fracture pattern.

Mean (SD) displacement of the fracture line between the ischium and stable fragment was 1.1 (0.9) mm for the standard implant and 0.8 (0.6) mm for the 3D printed implant, while the displacements of the fracture line between the stable fragment and anterior column were 0.6 (0.6) and 0.3 (0.3) for the standard and 3D printed methods, respectively (p < 0.001). Mean (SD) fracture line step-off at any fracture line for the standard implant was 1.2 (0.9) mm and 0.4 (0.4) mm for the 3D printed implant (p = 0.022).

Patient-specific 3D printed plates and drill guides may facilitate retaining accurate reduction and fixation of select acetabular fracture patterns.