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Low Elastic Modulus Titanium Alloy Pedicle Screws Reduce the Risk of Screw Loosening: A Pre-Clinical Biosafety and
Jinhui Liu1, Wenqiang Xu2, Lijunpeng Jia3
1Sichuan Provincial Laboratory of Orthopaedic Engineering, Department of Bone and Joint Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province, P.R. China.
Background:
The exacerbation of interfacial stiffness differences can lead to localized stress concentration and an increased incidence of pedicle screw loosening. Consequently, the etiology behind the higher occurrence of screw loosening in osteoporotic patients stems not only from a reduction in bone strength but also from a progressive decline in bone elastic modulus. In this context, we hypothesize that constructing pedicle screws using materials with low elastic modulus may help mitigate stiffness discrepancies at the bone-screw interface, potentially serving as an alternative biomechanical strategy to reduce the incidence of screw loosening.
Methods:
In vitro experiments were conducted to evaluate the biosafety of the novel low elastic modulus titanium alloy, Ti2448. This assessment was performed through various methods including the CCK-8 assay, flow cytometry, live and dead cell staining, and lactate dehydrogenase detection. In-vivo insertion of Ti2448 block have also been performed to assess whether it caused a local inflammatory response. Subsequently, conventional and low elastic modulus titanium alloy pedicle screws with identical shapes are machined. A comprehensive biomechanical study, comprising mechanical tests and numerical simulations, was conducted using an osteoporotic test block to evaluate the impact of reduced differences in bone-screw interfacial stiffness on local stress distribution and screw anchorage capability.
Results:
The ideal biosafety of the Ti2448 has been demonstrated through both in vitro and in vivo examinations. Furthermore, when compared to traditional titanium alloy, screws with a low elastic modulus exhibit superior anchorage capabilities in mechanical testing. Correspondingly, mechanical simulations indicate that the low elastic modulus screw can reduce interfacial stiffness differences, thereby alleviating stress concentration at the bone-screw interface.
Conclusions:
Low elastic modulus titanium alloy pedicle screws, characterized by their excellent biosafety, represent a viable alternative for the internal fixation of osteoporotic patients. This innovative approach aims to minimize interfacial stress concentration and mitigate the risk of screw loosening.
Level Of Evidence:
IV; basic science and biomechanical study.
