title: The mechanical benefit of medial support screws in locking plating of proximal humerus fractures.
abstract: BACKGROUND
  The purpose of this study was to evaluate the biomechanical advantages of medial support screws (MSSs) in the locking proximal humeral plate for treating proximal humerus fractures.
  
  
  METHODS
  Thirty synthetic left humeri were randomly divided into 3 subgroups to establish two-part surgical neck fracture models of proximal humerus. All fractures were fixed with a locking proximal humerus plate. Group A was fixed with medial cortical support and no MSSs; Group B was fixed with 3 MSSs but without medial cortical support; Group C was fixed with neither medial cortical support nor MSSs. Axial compression, torsional stiffness, shear stiffness, and failure tests were performed.
  
  
  RESULTS
  Constructs with medial support from cortical bone showed statistically higher axial and shear stiffness than other subgroups examined (P<0.0001). When the proximal humerus was not supported by medial cortical bone, locking plating with medial support screws exhibited higher axial and torsional stiffness than locking plating without medial support screws (P ≤ 0.0207). Specimens with medial cortical bone failed primarily by fracture of the humeral shaft or humeral head. Specimens without medial cortical bone support failed primarily by significant plate bending at the fracture site followed by humeral head collapse or humeral head fracture.
  
  
  CONCLUSIONS
  Anatomic reduction with medial cortical support was the stiffest construct after a simulated two-part fracture. Significant biomechanical benefits of MSSs in locking plating of proximal humerus fractures were identified. The reconstruction of the medial column support for proximal humerus fractures helps to enhance mechanical stability of the humeral head and prevent implant failure.
authors.affiliation: Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedics, Zhuhai People's Hospital, Jinan University Affiliated Zhuhai Hospital, Guangdong, China.
authors.forename: Langqing
authors.initials: L
authors.lastname: Zeng
authors.affiliation: Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Changqing
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Bingfang
authors.initials: B
authors.lastname: Zeng
authors.affiliation: Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D005593:Fracture Fixation, Internal; D006801:Humans; D012784:Shoulder Fractures / Q000628:therapy*
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