title: Biomechanical characteristics of fixation methods for floating pubic symphysis.
abstract: BACKGROUND
  Floating pubic symphysis (FPS) is a relatively rare injury caused by high-energy mechanisms. There are several fixation methods used to treat FPS, including external fixation, subcutaneous fixation, internal fixation, and percutaneous cannulated screw fixation. To choose the appropriate fixation, it is necessary to study the biomechanical performance of these different methods. The goal of this study was to compare the biomechanical characteristics of six methods by finite element analysis.
  
  
  METHODS
  A three-dimensional finite element model of FPS was simulated. Six methods were used in the FPS model, including external fixation (Ext), subcutaneous rod fixation (Sub-rod), subcutaneous plate fixation (Sub-plate), superior pectineal plate fixation (Int-sup), infrapectineal plate fixation (Int-ifa), and cannulated screw fixation (Int-scr). Compressive and rotational loads were then applied in all models. Biomechanical characteristics that were recorded and analyzed included construct stiffness, micromotion of the fracture gaps, von Mises stress, and stress distribution.
  
  
  RESULTS
  The construct stiffness of the anterior pelvic ring was decreased dramatically when FPS occurred. Compressive stiffness was restored by the three internal fixation and Sub-rod methods. Unfortunately, rotational stiffness was not restored satisfactorily by the six methods. For micromotion of the fracture gaps, the displacement was reduced significantly by the Int-sup and Int-ifa methods under compression. The internal fixation methods and Sub-plate method performed well under rotation. The maximum von Mises stress of the implants was not large. For the plate-screw system, the maximum von Mises stress occurred over the region of the fracture and plate-screw joints. The maximum von Mises stress appeared on the rod-screw and screw-bone interfaces for the rod-screw system.
  
  
  CONCLUSIONS
  The present study showed the biomechanical advantages of internal fixation methods for FPS from a finite element view. Superior stabilization of the anterior pelvic ring and fracture gaps was obtained by internal fixation. Subcutaneous fixation had satisfactory outcomes as well. Sub-rod fixation offered good anti-compression, while the Sub-plate fixation provided favorable anti-rotational capacity.
authors.affiliation: Department of Orthopedic Surgery, Shandong Provincial Hospital Affiliated to Shandong University, 324 Jingwu Road, Ji'nan, Shandong, People's Republic of China.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Song
authors.affiliation: Department of Orthopedic Surgery, Shandong Provincial Hospital Affiliated to Shandong University, 324 Jingwu Road, Ji'nan, Shandong, People's Republic of China. 408992708@qq.com.
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Zhou
authors.affiliation: Department of Orthopedic Surgery, Shandong Provincial Hospital Affiliated to Shandong University, 324 Jingwu Road, Ji'nan, Shandong, People's Republic of China. heyuworkmail@sina.com.
authors.forename: Yu
authors.initials: Y
authors.lastname: He
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D020342:Finite Element Analysis; D005592:Fracture Fixation / Q000295:instrumentation / Q000379:methods*; D005593:Fracture Fixation, Internal / Q000379:methods; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D011631:Pubic Symphysis / Q000293:injuries* / Q000503:physiopathology / Q000601:surgery*; D046548:Pubic Symphysis Diastasis / Q000503:physiopathology / Q000601:surgery
keywords: Biomechanical characteristics; External fixation; Floating pubic symphysis; Internal fixation; Subcutaneous fixation