title: Biomechanical analyses of static and dynamic fixation techniques of retrograde interlocking femoral nailing using nonlinear finite element methods.
abstract: Femoral shaft fractures can be treated using retrograde interlocking nailing systems; however, fracture nonunion still occurs. Dynamic fixation techniques, which remove either the proximal or distal locking screws, have been used to solve the problem of nonunion. In addition, a surgical rule for dynamic fixation techniques has been defined based on past clinical reports. However, the biomechanical performance of the retrograde interlocking nailing systems with either the traditional static fixation technique or the dynamic fixation techniques has not been investigated by using nonlinear numerical modeling. Three-dimensional nonlinear finite element models were developed, and the implant strength, fixation stability, and contact area of the fracture surfaces were evaluated. Three types of femoral shaft fractures (a proximal femoral shaft fracture, a middle femoral shaft fracture, and a distal femoral shaft fracture) fixed by three fixation techniques (insertion of all the locking screws, removal of the proximal locking screws, or removal of the distal locking screws) were analyzed. The results showed that the static fixation technique resulted in sufficient fixation stability and that the dynamic fixation techniques decreased the failure risk of the implant and produced a larger contact area of the fracture surfaces. The outcomes of the current study could assist orthopedic surgeons in comprehending the biomechanical performances of both static and dynamic fixation techniques. In addition, the surgeons could also select a fixation technique based on the specific patient situation using the numerical outcomes of this study.
authors.affiliation: Department of Orthopedic Surgery, Shin Kong Wu Ho-Su Memorial Hospital, Taipei 111, Taiwan, ROC; College of Medicine, Fu Jen Catholic University, Taipei 242, Taiwan, ROC; School of Medicine, Taipei Medical University, Taipei 110, Taiwan, ROC; Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, ROC.
authors.forename: Kao-Shang
authors.initials: KS
authors.lastname: Shih
authors.affiliation: Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan, ROC. Electronic address: hsucc@mail.ntust.edu.tw.
authors.forename: Ching-Chi
authors.initials: CC
authors.lastname: Hsu
authors.affiliation: Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, ROC.
authors.forename: Tzu-Pin
authors.initials: TP
authors.lastname: Hsu
authors.affiliation: Department of Orthopedic Surgery, Shin Kong Wu Ho-Su Memorial Hospital, Taipei 111, Taiwan, ROC.
authors.forename: Sheng-Mou
authors.initials: SM
authors.lastname: Hou
authors.affiliation: Department of Orthopedic Surgery, Shin Kong Wu Ho-Su Memorial Hospital, Taipei 111, Taiwan, ROC.
authors.forename: Chen-Kun
authors.initials: CK
authors.lastname: Liaw
mesh_terms: D001858:Bone Nails; D005269:Femur / Q000601:surgery*; D020342:Finite Element Analysis; D006801:Humans; D017711:Nonlinear Dynamics
keywords: Dynamization; Femoral fracture; Finite element analysis; Retrograde interlocking nail