The novel magnesium-titanium hybrid cannulated screws for the treatment of vertical femoral neck fractures: Biomechanical evaluation

Qida Zhang; Zhenxian Chen; Yinghu Peng; Zhongmin Jin; Ling Qin

doi:10.1016/j.jot.2023.08.003

The novel magnesium-titanium hybrid cannulated screws for the treatment of vertical femoral neck fractures: Biomechanical evaluation

J Orthop Translat. 2023 Sep 2:42:127-136. doi: 10.1016/j.jot.2023.08.003. eCollection 2023 Sep.

Authors

Qida Zhang¹, Zhenxian Chen², Yinghu Peng³, Zhongmin Jin^{4

5}, Ling Qin¹

Affiliations

¹ Musculoskeletal Research Laboratory, Department of Orthopaedics & Traumatology, The Chinese University of Hong Kong, Hong Kong.
² Key Laboratory of Road Construction Technology and Equipment (Ministry of Education), School of Mechanical Engineering, Chang'an University, Xi'an, China.
³ CAS Key Laboratory of Human-Machine Intelligence-Synergy Systems, Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences, Shenzhen, China.
⁴ Tribology Research Institute, School of Mechanical Engineering, Southwest Jiaotong University, Chengdu, China.
⁵ Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK.

Abstract

Background: Conventional cannulated screws are commonly used for internal fixation in the treatment of vertical femoral neck fractures. However, the noticeably high rates of undesirable outcomes such as nonunion, malunion, avascular necrosis, and fixation failure still troubled the patients and surgeons. It is urgent to develop new cannulated screws to improve the above clinical problems. The purpose of this study was to design a novel magnesium-titanium hybrid cannulated screw and to further evaluate its biomechanical performance for the treatment of vertical femoral neck fractures.

Methods: A novel magnesium-titanium hybrid cannulated screw was designed, and the conventional titanium cannulated screw was also modeled. The finite element models for vertical femoral neck fractures with magnesium-titanium hybrid cannulated screws and conventional cannulated screws were respectively established. The hip joint contact force during walking gait calculated by a subject-specific musculoskeletal multibody dynamics model, was used as loads and boundary conditions for both finite element models. The stress and displacement distributions of the cannulated screws and the femur, the micromotion of the fracture surfaces of the femoral neck, and the overall stiffness were calculated and analyzed using finite element models. The biomechanical performance of the Magnesium-Titanium hybrid cannulated screws was evaluated.

Results: The maximum stresses of the magnesium-titanium hybrid cannulated screws and the conventional cannulated screws were 451.5 MPa and 476.8 MPa, respectively. The maximum stresses of the femur with the above different cannulated screws were 140.3 MPa and 164.8 MPa, respectively. The maximum displacement of the femur with the hybrid cannulated screws was 6.260 mm, lower than the femur with the conventional cannulated screws, which was 7.125 mm. The tangential micromotions in the two orthogonal directions at the fracture surface of the femoral neck with the magnesium-titanium hybrid cannulated screws were comparable to those with the conventional cannulated screws. The overall stiffness of the magnesium-titanium hybrid cannulated screw system was 490.17 N/mm, higher than that of the conventional cannulated screw system, which was 433.92 N/mm.

Conclusion: The magnesium-titanium hybrid cannulated screw had superior mechanical strength and fixation stability for the treatment of the vertical femoral neck fractures, compared with those of the conventional cannulated screw, indicating that the magnesium-titanium hybrid cannulated screw has great potential as a new fixation strategy in future clinical applications.The translational potential of this article: This study highlights an innovative design of the magnesium-titanium hybrid cannulated screw for the treatment of vertical femoral neck fractures. The novel magnesium-titanium hybrid cannulated screw not only to provide sufficient mechanical strength and fixation stability but also to contribute to the promotion of fracture healing, which could provide a better treatment for the vertical femoral neck fractures, beneficially reducing the incidence of nonunion and reoperation rates.

Keywords: Biomechanics; Cannulated screws; Finite element analysis; Musculoskeletal multibody model; Vertical femoral neck fractures.