Archives of Orthopaedic and Trauma Surgery

, Volume 139, Issue 8, pp 1069–1074 | Cite as

The influence of screw length on predicted cut-out failures for proximal humeral fracture fixations predicted by finite element simulations

  • James W. A. Fletcher
  • Markus Windolf
  • Leonard Grünwald
  • R. Geoff Richards
  • Boyko Gueorguiev
  • Peter VargaEmail author
Trauma Surgery



The aim of this study was to identify the effect of screw length on predictions of fixation failure in three-part proximal humeral fractures using a finite element-based osteosynthesis modelling toolkit.


A mal-reduced unstable three-part AO/OTA 11-B3.2 fracture with medial comminution was simulated in forty-two digitally processed proximal humeri covering a spectrum of bone densities and fixed with the PHILOS plate using three distal and six proximal locking screws. Four test groups were generated based on the screw tip to joint surface distance (TJD), with all proximal screws being shortened from 4 mm TJD to be 8, 12 or 16 mm TJD. Average bone strains around the screw tips, correlating with biomechanical cyclic cut-out-type failure, were evaluated in three physiological loading protocols representing simple shoulder motions. Six further groups were tested, where five of the proximal screws were inserted to 4 mm TJD and the sixth screw to 8 mm TJD.


Exponential increases in the predicted risk of fixation failure were seen with increased tip-to-joint distances (p < 0.001). When one of the proximal screws was placed 8 mm from the joint, with the remaining five at 4 mm distance, significant increases (p < 0.001) were registered in the strains around the screw tips in all except the two superior screws. This effect was maximal around the calcar screws (p < 0.001) and for lower density samples (p < 0.001).


These results suggest that longer screws provide reduced risk of cut-out failure, i.e. distalisation and/or varisation of the head fragment, and thus may decrease failure rates in proximal humeral fractures treated with angular stable plates. These findings require clinical corroboration and further studies to investigate the risk of screw perforation.


Proximal humerus fracture Locking plate fixation PHILOS plate Fixation failure Screw length Finite element analysis 



This study was performed with the assistance of the AO Foundation via the AOTRAUMA Network (Grant No.: AR2013_01).

Compliance with ethical standards

Conflict of interest

The authors are not compensated and there are no other institutional subsidies, corporate affiliations, or funding sources supporting this work unless clearly documented and disclosed.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.AO Research Institute DavosDavosSwitzerland
  2. 2.Department for HealthUniversity of BathBathUK
  3. 3.Department of Traumatology and Orthopedic SurgeryKlinikum EsslingenEsslingenGermany

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