title: Role of the compression screw in the dynamic hip-screw system: A finite-element study.
abstract: The dynamic hip-screw (DHS) system is a common implant for fixation of proximal femur fractures. During assembly, it has been recommended to remove the compression screw after initial compression has been obtained; however, related complications had been reported. So far, the role of compression screw in the reconstructed stability of hip fractures as well as the mechanical strength of the DHS system has rarely been mentioned. This study investigated the function of this screw in the DHS system during fracture healing. Based on the FE method, six numerical models of proximal femur were employed to analyze the mechanical response of a DHS implant with various fracture types and different fixation strategies (with or without a compression screw). The displacement of the femur head and peak von Mises stress were selected as indices of the stability of a fractured femur stabilized by a DHS device and of the risk of implant failure, respectively. Our results showed that a retained compression screw increased reconstructed structural stiffness, reducing the displacement of the femur head. This screw also helped to lessen mechanical failure of side plate by reducing the peak von Mises stress around the connection between the barrel and side plate. Both findings were evident in the proximal femur fracture involving the intertrochanteric part, and even more obvious in the setting of bony defects. Thus, we recommend the maintenance of compression screw in the DHS system while treating the intertrochanteric fracture, particularly in cases with bony defects.
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan; Department of Orthopedics, National Cheng Kung University Hospital, Tainan City, Taiwan.
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Chang
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan; Metal Industries Research & Development Centre, Kaohsiung City, Taiwan. Electronic address: yennien.chen@gmail.com.
authors.forename: Yen-Nien
authors.initials: YN
authors.lastname: Chen
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan.
authors.forename: Chun-Ting
authors.initials: CT
authors.lastname: Li
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan.
authors.forename: Yao-Te
authors.initials: YT
authors.lastname: Peng
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan.
authors.forename: Chih-Han
authors.initials: CH
authors.lastname: Chang
mesh_terms: D001863:Bone Screws; D005264:Femoral Fractures / Q000601:surgery; D020342:Finite Element Analysis; D006615:Hip / Q000601:surgery; D055595:Mechanical Phenomena; D013314:Stress, Mechanical
keywords: Compression screw; Dynamic hip–screw (DHS) system; Finite element (FE)