title: [Biomechanical study of percutaneous pinning as the treatment of proximal humerus fractures].
abstract: OBJECTIVE
  To investigate the influence on fracture stability by different pin construct during percutaneous pinning for the treatment of proximal humerus fractures.
  
  
  METHODS
  Eighteen pairs (36) adult fresh-frozen humeri were match-paired and divided into 4 groups. Dual-energy bone density scan had been used in order to rule out the influence by different degrees of osteoporosis of the cadaver. Two-part surgical neck fracture model was carried out unanimously in all 36 humeri. Four terminal threaded pins (2.5 mm in diameter) were used in fixation for all specimen. Parallel type pinning (box type) were carried out in 2 groups and convergent type pinning (fan shape) in the other 2 groups. Instron5566 biomechanical tester was applied in determining both anti-shear and anti-torsion ultimate load of each specimen.
  
  
  RESULTS
  There was no statistical difference between parallel pin construct and convergent construct in regard of anti-shear resistance (P = 0.73). But by mean of anti-torsion resistance, the parallel construct had significant advantage over the convergent construct (P = 0.04).
  
  
  CONCLUSIONS
  According to our biomechanical data, parallel pin construct seems to have better torsional stability. We suggest that parallel pin fixation should be applied whenever possible. Convergent pin construct should be considered when parallel construct is not possible or the distance between pins are too small (< 1 cm).
authors.affiliation: Department of Orthopeadic and Traumatology, Beijing Jishuitan Hospital, Beijing 100035, China.
authors.forename: Chun-yan
authors.initials: CY
authors.lastname: Jiang
authors.forename: Man-yi
authors.initials: MY
authors.lastname: Wang
authors.forename: Guo-wei
authors.initials: GW
authors.lastname: Rong
mesh_terms: D001696:Biomechanical Phenomena; D001858:Bone Nails; D002102:Cadaver; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D012784:Shoulder Fractures / Q000503:physiopathology / Q000601:surgery*