gms | German Medical Science

German Congress of Orthopaedics and Traumatology (DKOU 2016)

25.10. - 28.10.2016, Berlin

Biomechanical evaluation of straight antegrade nailing in proximal humeral fractures: The rationale of the "fifth anchoring point"

Meeting Abstract

  • presenting/speaker Simon Euler - Medizinische Universität Innsbruck, Klinik für Unfallchirurgie und Sporttraumatologie, Innsbruck, Austria
  • Maximilian Petri - Medizinische Hochschule Hannover, Hannover, Germany
  • Melanie B Venderley - Steadman Philippon Research Institute, Vail, CO, United States
  • Grant J. Dornan - Steadman Philippon Research Institute, Vail, CO, United States
  • Werner Schmölz - Univ.-Klinik für Unfallchirurgie, Innsbruck, Austria
  • Travis L Turnbull - Steadman Philippon Research Institute, Vail, CO, United States
  • Franz S Kralinger - Wilhelminenspital Wien, Abteilung für Unfallchirurgie und Sporttraumatologie, Wien, Austria
  • Peter J. Millett - The Steadman Clinic, Director of Shoulder Surgery, Vail, United States

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2016). Berlin, 25.-28.10.2016. Düsseldorf: German Medical Science GMS Publishing House; 2016. DocGR21-142

doi: 10.3205/16dkou487, urn:nbn:de:0183-16dkou4878

Published: October 10, 2016

© 2016 Euler et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at



Objectives: Varus failure is one of the most common failure modes following surgical treatment of proximal humeral fractures. Anchoring the most densely zone of the proximal humerus (subchondral zone) with the nail's end, straight antegrade nails (SAN) theoretically provide increased stability. The aim of this study was to biomechanically investigate the characteristics of this so called "fifth anchoring point" (FAP). We hypothesized that this additional proximal anchoring point would improve stability compared to the same construct without the FAP.

Methods: SAN was performed in 20 matched-pairs of human cadaveric humeri for a simulated unstable two-part fracture and a comminuted medial calcar.

Results and Conclusion: Biomechanical testing with stepwise increasing cyclic axial loading (50 N increments each 100 cycles) at an angle of 20° abduction revealed significantly higher median loads to failure for SAN constructs with the FAP (median 450 N, range 200 - 1000 N) compared to those without the FAP (median 325 N, range 100 - 500 N; p=0.009). SAN constructs with press-fit proximal extensions (endcaps) showed similar median loads to failure (median 400 N, range 200 - 650 N) when compared to the undersized SANs endcaps, commonly available on the market (median 450 N, range 200 - 600 N; p=0.240).

The FAP provided significantly increased stability in SAN constructs compared to the same setup without this additional proximal anchoring point. In constructs with the FAP, varus-displacing forces to the humeral head were superiorly reduced in this setting. This study lends biomechanical evidence to approve the "fifth anchoring point's" rationale. According to our findings, straight antegrade humeral nailing may be beneficial for patients undergoing surgical treatment for unstable and medially comminuted proximal humeral fractures to decrease secondary varus displacement and to therefore potentially reduce revision rates.