Open Access Research article

Mechanical testing of a device for subcutaneous internal anterior pelvic ring fixation versus external pelvic ring fixation

Georg Osterhoff1*, Simon Tiziani1, Stephen J Ferguson2, Gregor Spreiter2, Max J Scheyerer1, Gian-Leza Spinas1, Guido A Wanner1, Hans-Peter Simmen1 and Clément ML Werner1

Author Affiliations

1 Division of Trauma Surgery, University of Zurich, Raemistrasse 100, Zurich 8091, Switzerland

2 Institute for Biomechanics, ETH Zurich, HCI-E355.2 Wolfgang-Pauli-Strasse 10, Zurich 8093, Switzerland

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BMC Musculoskeletal Disorders 2014, 15:111  doi:10.1186/1471-2474-15-111

Published: 31 March 2014



Although useful in the emergency treatment of pelvic ring injuries, external fixation is associated with pin tract infections, the patient’s limited mobility and a restricted surgical accessibility to the lower abdomen. In this study, the mechanical stability of a subcutaneous internal anterior fixation (SIAF) system is investigated.


A standard external fixation and a SIAF system were tested on pairs of Polyoxymethylene testing cylinders using a universal testing machine. Each specimen was subjected to a total of 2000 consecutive cyclic loadings at 1 Hz with sinusoidal lateral compression/distraction (+/−50 N) and torque (+/− 0.5 Nm) loading alternating every 200 cycles. Translational and rotational stiffness were determined at 100, 300, 500, 700 and 900 cycles.


There was no significant difference in translational stiffness between the SIAF and the standard external fixation when compared at 500 (p = .089), 700 (p = .081), and 900 (p = .266) cycles. Rotational stiffness observed for the SIAF was about 50 percent higher than the standard external fixation at 300 (p = .005), 500 (p = .020), and 900 (p = .005) cycles. No loosening or failure of the rod-pin/rod-screw interfaces was seen.


In comparison with the standard external fixation system, the tested device for subcutaneous internal anterior fixation (SIAF) in vitro has similar translational and superior rotational stiffness.

Pelvic fracture; Pelvic ring injury; Internal fixation; External fixation; Subcutaneous internal anterior fixation