title: Finite element analysis of the three different posterior malleolus fixation strategies in relation to different fracture sizes.
abstract: OBJECTIVE
  Appropriate fixation method for the posterior malleolar fractures (PMF) according to the fracture size is still not clear. Aim of this study was to evaluate the outcomes of the different fixation methods used for fixation of PMF by finite element analysis (FEA) and to compare the effect of fixation constructs on the size of the fracture computationally.
  
  
  METHODS
  Three dimensional model of the tibia was reconstructed from computed tomography (CT) images. PMF of 30%, 40% and 50% fragment sizes were simulated through computational processing. Two antero-posterior (AP) lag screws, two postero-anterior (PA) lag screws and posterior buttress plate were analysed for three different fracture volumes. The simulated loads of 350N and 700N were applied to the proximal tibial end. Models were fixed distally in all degrees of freedom.
  
  
  RESULTS
  In single limb standing condition, the posterior plate group produced the lowest relative displacement (RD) among all the groups (0.01, 0.03 and 0.06mm). Further nodal analysis of the highest RD fracture group showed a higher mean displacement of 4.77mm and 4.23mm in AP and PA lag screws model (p=0.000). The amounts of stress subjected to these implants, 134.36MPa and 140.75MPa were also significantly lower (p=0.000). There was a negative correlation (p=0.021) between implant stress and the displacement which signifies a less stable fixation using AP and PA lag screws.
  
  
  CONCLUSIONS
  Progressively increasing fracture size demands more stable fixation construct because RD increases significantly. Posterior buttress plate produces superior stability and lowest RD in PMF models irrespective of the fragment size.
authors.affiliation: Department of Orthopaedic Surgery, The First Affiliated Hospital of Dalian Medical University, 222 Zhongshan Road, 116011 Dalian, Liaoning, PR China. Electronic address: adeelanwardmu@163.com.
authors.forename: Adeel
authors.initials: A
authors.lastname: Anwar
authors.affiliation: Department of Orthopaedic Surgery, The First Affiliated Hospital of Dalian Medical University, 222 Zhongshan Road, 116011 Dalian, Liaoning, PR China. Electronic address: lvdecheng_dmu@163.com.
authors.forename: Decheng
authors.initials: D
authors.lastname: Lv
authors.affiliation: Department of Orthopaedic Surgery, The Second Affiliated Hospital of Dalian Medical University, 456 Zhongshan Road, 116027 Dalian, Liaoning, PR China. Electronic address: zhaozhidl@126.com.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Department of Orthopaedic Surgery, The First Affiliated Hospital of Dalian Medical University, 222 Zhongshan Road, 116011 Dalian, Liaoning, PR China. Electronic address: doctorzz@126.com.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedic Surgery, The First Affiliated Hospital of Dalian Medical University, 222 Zhongshan Road, 116011 Dalian, Liaoning, PR China. Electronic address: dllm@2008.sina.com.
authors.forename: Ming
authors.initials: M
authors.lastname: Lu
authors.affiliation: Muhammad Umar Nazir, Department of Respiratory Medicine, The Second Affiliated Hospital of Dalian Medical University, 456 Zhongshan Road, 116027 Dalian, Liaoning, PR China. Electronic address: umar475@hotmail.com.
authors.forename: Muhammad Umar
authors.initials: MU
authors.lastname: Nazir
authors.affiliation: Wasim Qasim, Department of General Surgery, The Second Affiliated Hospital of Dalian Medical University, 456 Zhongshan Road, 116027 Dalian, Liaoning, PR China. Electronic address: wasim_qasim44@yahoo.com.
authors.forename: Wasim
authors.initials: W
authors.lastname: Qasim
mesh_terms: D064386:Ankle Fractures / Q000145:classification / Q000000981:diagnostic imaging* / Q000601:surgery; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D020342:Finite Element Analysis; D005593:Fracture Fixation, Internal; D006801:Humans; D021621:Imaging, Three-Dimensional; D013314:Stress, Mechanical; D013639:Tarsal Bones / Q000000981:diagnostic imaging*; D013977:Tibia / Q000000981:diagnostic imaging*; D016474:Weight-Bearing
keywords: Finite element analysis; Fracture fixation; Fracture size; Implants; Posterior malleolar fracture; Relative displacement; Stability; Stress; Three dimensional model