title: Plate fixation for Letenneur type I Hoffa fracture: a biomechanical study.
abstract: BACKGROUND
  A coronal fracture of the posterior femoral condyle, also known as a Hoffa fracture, is an unusual injury, and there are only a handful of case reports or series exploring it. The optimal fixation method of these intraarticular fractures remains controversial; improper or unstable fixation usually lead to an unsatisfactory prognosis. The use of posterior-anterior or reversed lag screw fixation is still a popular method. Additional buttress plating is also recommended for fixation of these difficult fractures. The purpose of this study was to compare the mechanical strength of four different fixation patterns for this uncommon fracture.
  
  
  METHODS
  Sixteen sawbone simulated models of Letenneur type I Hoffa fractures were created with one of four fixation patterns: two screws implanted in the anterior-posterior (AP) direction or posterior-anterior (PA) direction; one screw in the PA direction with a plate implanted in the posterior position of the distal femoral condyle or with a plate in the lateral position. Biomechanical testing was performed to determine the post-fixation axial stiffness, the maximum load to failure and the fragment vertical displacement for each of the four constructs.
  
  
  RESULTS
  The plate fixation patterns whether implanted in the posterior or lateral position were shown to provide higher overall axial stiffness and load to failure, and less vertical displacement than the other two patterns of pure screw fixation. Among these constructs, the lateral plate fixation was found to provide the highest stiffness and load to failure and the least displacement for the posterior condylar fragments, followed by the posterior plate fixation. The lowest overall stiffness and load to failure and the largest vertical displacement were found in the construct with the AP direction placed screws.
  
  
  CONCLUSIONS
  It was concluded that the lateral position implanted plate is biomechanically the strongest fixation method for Letenneur type I Hoffa fractures. However, this plate fixation is not recommended for all cases. The choice of internal fixation pattern depends on the surgeons.
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 YiShan Road, Shanghai 200233, China. Electronic address: sunshine20002000@126.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 YiShan Road, Shanghai 200233, China. Electronic address: heqifang1982@126.com.
authors.forename: Qi-Fang
authors.initials: QF
authors.lastname: He
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 YiShan Road, Shanghai 200233, China. Electronic address: Huangyigang@163.com.
authors.forename: Yi-Gang
authors.initials: YG
authors.lastname: Huang
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 YiShan Road, Shanghai 200233, China. Electronic address: pansmith@163.com.
authors.forename: Jian-Feng
authors.initials: JF
authors.lastname: Pan
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 YiShan Road, Shanghai 200233, China. Electronic address: luocong_feng@163.com.
authors.forename: Cong-Feng
authors.initials: CF
authors.lastname: Luo
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 YiShan Road, Shanghai 200233, China. Electronic address: chaiyimin@outlook.com.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Chai
mesh_terms: D001187:Artificial Organs; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D001842:Bone and Bones / Q000601:surgery; D005264:Femoral Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D008953:Models, Anatomic; D019637:Orthopedic Procedures; D000066908:Simulation Training; D013314:Stress, Mechanical; D013718:Tensile Strength
keywords: Biomechanics; Hoffa fracture; Internal fixation; Letenneur classification