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Accessible Unlicensed Requires Authentication Published by De Gruyter April 1, 2012

Development of a test system to analyze different hip fracture osteosyntheses under simulated walking

Andreas Lenich, Samuel Bachmeier, Sebastian Dendorfer, Edgar Mayr, Michael Nerlich and Bernd Füchtmeier
From the journal

Abstract

The mechanical complications of osteosyntheses after hip fractures are previously investigated by mostly static or dynamic uniaxial loading test systems. However, the physiologic loading of the hip joint during a normal gait is a multiplanar, dynamic movement. Therefore, we constructed a system to test osteosyntheses for hip fractures under physiologic multiplanar loading representative of normal gait. To evaluate the testing system, 12 femora pairs were tested under 25,000 cycles with two standard osteosyntheses (Proximal Femoral Nail Antirotation/Gamma3 Nail). For angular movement, the varus collapse to cut out (∝CO) (∝CO=4.8°±2.1° for blade and ∝CO=7.8°±3.8° for screw) was the dominant failure mode, and only slight rotational angle shifts (∝Rot) (∝Rot=1.7°±0.4° for blade and ∝Rot=2.4°±0.3° for screw) of the femoral head around the implant axis were observed. Angular displacements in varus direction and rotation were higher in specimens reinforced with screws. Hence, the cut out model and the migration directions showed a distinction between helical blade and hip screw. However, there were no significant differences between the different implants. The new setup is able to create clinical failures and allows to give evidence about the anchorage stability of different implant types under dynamic gait motion pattern.


Corresponding author: Dr. Andreas Lenich, Department of Trauma Surgery, Klinikum Rechts der Isar, Technical University of Munich, Ismaningerstr 22, D-81675 Munich, Germany Phone: +49-89-41405026

Received: 2010-7-28
Accepted: 2012-2-14
Published Online: 2012-04-01
Published in Print: 2012-04-01

©2012 by Walter de Gruyter Berlin Boston