The effects of fixation methods on the biomechanics of comminuted distal metaphyseal tibia fractures

Bone fractures require the proper integration of fixation devices to ensure long-term biomechanical performance and accelerated recovery, while allowing for early load-bearing and equitable load-sharing. The primary objective of this research is to elucidate the effect of four different generations of fixation devices on synthetic tibiae with induced comminuted fractures. The fixation devices considered herein comprised an intramedullary nail, as well as various distal interlocking screws and plates. The overall biomechanical response was studied under quasi-static compressive loading, following cyclic testing to evaluate the overall system stiffness. More advanced generations (Gen III and IV) showed increased stiffness, reaching values of 1304.69 ± 2.90 kN/m and 1461.00 ± 2.98 kN/m, respectively. Cyclic compressive tests were performed before load-to-failure studies, with the biomechanical constructs being instrumented with strain gauges affixed to the intramedullary nail distally and full-field digital image correlation proximally at the superior flat part of the tibia, revealing the load-sharing capabilities of each fixation device configuration throughout the cyclic loading scenario. The digital image correlation analysis revealed that the proximal tibia exhibited higher strain levels in fixation configurations with only two medial-to-lateral screws, further substantiating the importance of incorporating additional components into the bone-implant system to provide greater stabilization. The distal strain gauges, which registered the deformation of the intramedullary nails, revealed that Gen IV, the only configuration including a medial plate, proved to reduce instabilities in that area, thereby enhancing load sharing between the bone and the intramedullary nail. Ultimately, this extensive experimental work elucidates the importance of comprehensive distal tibiae fixations, which are paramount for future interventions, providing biomechanical stability and bone-implant load sharing. These outcomes are clinically relevant, potentially accelerating load-bearing after surgery by selecting the optimal fixation configuration based on patient conditions and improving the quality of life thereafter.