Biomechanical analysis of a novel locking plate with smooth pegs versus a conventional locking plate with threaded screws for proximal humerus fractures

Nobuyuki Yamamoto, Michio Hongo, Lawrence J. Berglund, John W. Sperling, Robert H. Cofield, Kai Nan An, Scott P. Steinmann

Research output: Contribution to journalArticle

15 Scopus citations


Background: Repair of proximal humeral fractures with locking plates has greatly improved outcomes. However, an alarming rate of complications including screw cutout and impingement under the acromion has recently been reported. A novel locking plate with smooth pegs was developed to reduce these risks. The purpose of this study was to compare these 2 fixation methods with a cadaveric biomechanical study. Materials and methods: Fourteen pairs of cadaveric proximal humeri (mean age, 77 years) were harvested, and bone density was measured. Osteosynthesis was performed on each pair using either a locking plate with threaded screws (TS group) or smooth pegs (SP group) on the contralateral side. Seven pairs of humeri were tested for cyclic bending, and 7 pairs for cyclic torsional evaluation: TS bending, SP bending, TS torsion, and SP torsion. The bending protocol consisted of cyclically loading to a maximum of 7.5 Nm bending moment for 10,000 cycles. The torsion protocol consisted of ±2 Nm of axial torque for 10,000 cycles. Surgical neck fractures were simulated by excising a 10-mm wedge of bone. Results: No implant failure or screw cutout was observed in any of the groups tested. Under bending loads, mean displacement of the distal fragment was significantly less for the SP group than that for the TS group over 5,000 cycles. In torsion tests, no significant differences were observed between the 2 fixation methods. Discussion: The SP group demonstrated superior biomechanical characteristics to the TS group in regards to cyclic bending.

Original languageEnglish (US)
Pages (from-to)445-450
Number of pages6
JournalJournal of Shoulder and Elbow Surgery
Issue number4
StatePublished - Apr 1 2013



  • Basic Science Study
  • Biomechanical Study
  • Locking plate
  • Screw cutout
  • Smooth peg

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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