title: Biomechanical investigation of titanium elastic nail prebending for treating diaphyseal long bone fractures.
abstract: This study numerically investigated the deformation of titanium elastic nails prebent at various degrees during implantation into the intramedullary canal of fractured bones and the mechanism by which this prebending influenced the stability of the fractured bone. Three degrees of prebending the implanted portions of the nails were used: equal to, two times, and three times the diameter of the intramedullary canal. Furthermore, a simulated diaphyseal fracture with a 5-mm gap was created in the middle shaft portion of the bone fixed with two elastic nails in a double C-type configuration. End caps were simulated using a constraint equation. To confirm that the simulation process is able to present the mechanical response of the nail inside the intramedullary, an experiment was conducted by using sawbone for validation. The results indicated that increasing the degrees of nail prebending facilitated straightening the nails against the inner aspect of canal after implantation, with increase in stability under torsion. Furthermore, reducing nail prebending caused a larger portion of the nails to move closer to the loading site and center of bone after implantation; the use of end caps prevented the nail tips from collapsing and increased axial stability. End cap use was critical for preventing the nail tips from collapsing and for increasing the stability of the nails prebent at a degree equal to the diameter of the canal with insufficient frictional force between the nail and canal. Therefore, titanium elastic nail prebending in a double C-type configuration with a degree three times the diameter of the canal represents a superior solution for treating transverse fractures without a gap, whereas that with a degree equal to the diameter of the intramedullary canal and combined with end cap use represents an advanced solution for treating comminuted fractures in a diaphyseal long bone fracture.
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Yen-Nien
authors.initials: YN
authors.lastname: Chen
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan, Taiwan.|Department of Orthopedics, Show-Chwan Memorial Hospital, Changhua, Taiwan.
authors.forename: Pei-Yuan
authors.initials: PY
authors.lastname: Lee
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan, Taiwan.|Department of Orthopedics, National Cheng Kung University Hospital, Tainan, Taiwan.
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Chang
authors.affiliation: Display Technology Center, Industrial Technology Research Institute, Hsinchu, Taiwan.
authors.forename: Yi-Hung
authors.initials: YH
authors.lastname: Ho
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan, Taiwan.|Metal Industries Research & Development Centre, Kaohsiung, Taiwan.
authors.forename: Yao-Te
authors.initials: YT
authors.lastname: Peng
authors.affiliation: Department of BioMedical Engineering, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Chih-Han
authors.initials: CH
authors.lastname: Chang
authors.affiliation: Graduate Institute of Mechatronic System Engineering, National University of Tainan, Tainan, Taiwan. ctli0412@gmail.com.
authors.forename: Chun-Ting
authors.initials: CT
authors.lastname: Li
mesh_terms: D001696:Biomechanical Phenomena / Q000187:drug effects; D001858:Bone Nails; D003198:Computer Simulation; D018483:Diaphyses / Q000187:drug effects / Q000503:physiopathology*; D004548:Elasticity; D050723:Fractures, Bone / Q000503:physiopathology* / Q000628:therapy*; D006801:Humans; D008962:Models, Theoretical; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D014025:Titanium / Q000494:pharmacology*
chemical_list: D014025:Titanium
keywords: Diaphyseal long bone fracture; Elastic stable intramedullary nail; End cap; Finite element method; Nail prebending