Data acquisition and analysis
fracture
DECAY
Machine data in terms of axial displacement (mm) and load (N) were acquired at 128 Hz. Based on them, the initial construct stiffness was calculated from the ascending load–displacement curve of the initial quasi-static ramp within the load range 50–90 N.Two optical cameras (Aramis SRX, Carl Zeiss GOM Metrology GmbH, Braunschweig, Germany), operating at 12 Megapixel, continuously recorded the three-dimensional positions of the attached markers at 20 Hz throughout the tests. Based on these, the relative movements between the medial and lateral aspects of the sacrum fracture were analyzed with respect to the marker positions at the beginning of the cyclic test, by means of calculation of the following parameters:gap angle—angular displacement describing the combined fracture gap opening in frontal and transverse plane;flexion—angular displacement describing relative fragment rotation in sagittal plane;total displacement—magnitude of the translational displacement of the fracture aspect lying most anteriorly in the fracture gap.Finally, to visually evaluate the gradual decay of the bone-implant constructs, antero-posterior X-rays were taken with a C-arm (Arcadis Varic, Siemens Healthineers, Erlangen, Germany) at test start, and then intermittently every 500 cycles in peak load condition. For that purpose, the cyclic test was interrupted for 2s in the corresponding load magnitude.The outcome measures of these parameters were evaluated in peak loading conditions over the first 18,000 cycles in equidistant intervals of 1000 cycles. This range was chosen, because beyond it, the first specimens dropped out due to their failure (Fig. Implant failure (TITS: transiliac–transsacral, SI: sacroiliacal)Statistical analysis was performed with SPSS Statistics (V21.0, IBM, Armonk, NY) and Graphpad (GraphPad Software, La Jolla California USA). Cohorts were tested with the Mann–Whitney 