Biomechanical characteristics of fixations parallel to the plateau and vertical to the fracture line in the early management of fractures of tibial plateau in rabbits

Abstract

Objective To evaluate the biomechanical characteristics of fixations parallel to the tibial plateau and vertical to the fracture line in the early management of fractures of tibial plateau in rabbits. Methods Models of oblique split fractures of the medial tibial plateau were created in 30 New Zealand rabbits of 13 months. One fibial plateau was fixed with 3 lag screws （2. 0 mm） parallel to the articular surface while the contralateral plateau was stabilized with 3 lag screws （2. 0 mm） vertical to the fracture line. The specimens were harvested at 0, 1, 2, 4, and 8 weeks after operation respectively and tested in a biomechanical testing machine. The maximum load of anti-compression at the medial tibial plateau and the maximum work at the maximum load, as well as the load and work as the articular surface displaced downwards for 2mm, were recorded. Results The biomechanical comparison of the 2 methods at the same time points showed that there were no significant differences at 0, 1 and 8 weeks but significant differences at 2 and 4 weeks. The biomechanical comparison of the same method at different time points showed that the biomechanical measures decreased at the early period after operation, then increased and finally kept steady at 4 or 8 weeks. Con- clusions The stability of tibial plateau fractures in rabbits decreases at the early post-operation and gradually increases to the normal level. It takes less time for the fixation parallel to the tibial plateau to increase the biomechanical stability to the normal level than the fixation vertical to the fracture line. The parallel fixation can provide more biomechanical advantage in stabilization of the fractures than the vertical one. Key words: Tibial fracture; Knee joint; Biomechanics