[Finite element study of three novel internal fixation modes for bicondylar four-quadrant fractures of tibial plateau].

OBJECTIVE

To compare the biomechanical differences among the three novel internal fixation modes in treatment of bicondylar four-quadrant fractures of the tibial plateau through finite-element technique, and find an internal fixation modes which was the most consistent with mechanical principles.

METHODS

Based on the CT image data of the tibial plateau of a healthy male volunteer, a bicondylar four-quadrant fracture model of the tibial plateau and three experimental internal fixation modes were established by using finite element analysis software. The anterolateral tibial plateaus of groups A, B, and C were fixed with inverted L-shaped anatomic locking plates. In group A, the anteromedial and posteromedial plateaus were longitudinally fixed with reconstruction plates, and the posterolateral plateau was obliquely fixed with reconstruction plate. In groups B and C, the medial proximal tibia was fixed with T-shaped plate, and the posteromedial plateau was longitudinally fixed with the reconstruction plate or posterolateral plateau was obliquely fixed with the reconstruction plate, respectively. An axial load of 1 200 N was applied to the tibial plateau (a simulation of a 60 kg adult walking with physiological gait), and the maximum displacement of fracture and maximum Von-Mises stress of the tibia, implants, and fracture line were calculated in 3 groups.

RESULTS

Finite element analysis showed that the stress concentration area of tibia in each group was distributed at the intersection between the fracture line and screw thread, and the stress concentration area of the implant was distributed at the joint of screws and the fracture fragments. When axial load of 1 200 N was applied, the maximum displacement of fracture fragments in the 3 groups was similar, and group A had the largest displacement (0.74 mm) and group B had the smallest displacement (0.65 mm). The maximum Von-Mises stress of implant in group C was the smallest (95.49 MPa), while that in group B was the largest (177.96 MPa). The maximum Von-Mises stress of tibia in group C was the smallest (43.35 MPa), and that in group B was the largest (120.50 MPa). The maximum Von-Mises stress of fracture line in group A was the smallest (42.60 MPa), and that in group B was the largest (120.50 MPa).

CONCLUSION

For the bicondylar four-quadrant fracture of the tibial plateau, a T-shaped plate fixed in medial tibial plateau has a stronger supporting effect than the use of two reconstruction plates fixed in the anteromedial and posteromedial plateaus, which should be served as the main plate. The reconstruction plate, which plays an auxiliary role, is easier to achieve anti-glide effect when it is longitudinally fixed in posteromedial plateau than obliquely fixed in posterolateral plateau, which contributes to the establishment of a more stable biomechanical structure.