A Novel Approach for Patellofemoral Tracking Using a Knee Model Reconstructed with a Three-Dimensional Printer

This study proposes a new approach to evaluate the patellofemoral tracking using a knee model composed of femur, tibia, and patella reconstructed with a three-dimensional (3D) printer. Magnetic resonance images were used to create a CAD (Computer-Aided Design) file that is subsequently used as input for a 3D printer machine. Artificial ligaments were used to mimic the stability of the knee. The quadriceps tendon was simulated using a polyvinylchloride cord attached to the tibial insertion and the patella. The model was fixed to a tensile test machine and four static tests were performed by applying 200 N load in the proximal–distal direction through the cord at 30°, 60°, and 90° of knee flexion. The position of the patella was measured using a motion-tracking system with a custom-made navigation system. The mediolateral displacement of the patella was 1.01 ± 0.13 mm at 30° of knee flexion and 7.99 ± 0.07 mm at 90° of flexion. The patella lateral tilt was 2.79° ± 0.67° at 30° of flexion and 6.42° ± 0.11° at 90° of flexion. In conclusion, our low-cost knee model closely simulates the patellar behavior of cadaveric specimens as the results are in agreement with literature data on similar static in vitro experiments.