Background: Although useful in the emergency treatment of pelvic ring injuries, external fixation is associated with\r\npin tract infections, the patient�s limited mobility and a restricted surgical accessibility to the lower abdomen. In this\r\nstudy, the mechanical stability of a subcutaneous internal anterior fixation (SIAF) system is investigated.\r\nMethods: A standard external fixation and a SIAF system were tested on pairs of Polyoxymethylene testing cylinders\r\nusing a universal testing machine. Each specimen was subjected to a total of 2000 consecutive cyclic loadings at 1 Hz\r\nwith sinusoidal lateral compression/distraction (+/-50 N) and torque (+/- 0.5 Nm) loading alternating every 200 cycles.\r\nTranslational and rotational stiffness were determined at 100, 300, 500, 700 and 900 cycles.\r\nResults: There was no significant difference in translational stiffness between the SIAF and the standard external\r\nfixation when compared at 500 (p = .089), 700 (p = .081), and 900 (p = .266) cycles. Rotational stiffness observed for the\r\nSIAF was about 50 percent higher than the standard external fixation at 300 (p = .005), 500 (p = .020), and 900 (p = .005)\r\ncycles. No loosening or failure of the rod-pin/rod-screw interfaces was seen.\r\nConclusions: In comparison with the standard external fixation system, the tested device for subcutaneous internal\r\nanterior fixation (SIAF) in vitro has similar translational and superior rotational stiffness.
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