Fabian M Stuby1, Stefan Doebele2, Yash Agarwal3, Markus Windolf4, Boyko Gueorguiev5, Bjoern Gunnar Ochs6. 1. BG Trauma Center, Eberhard Karls University, Schnarrenbergstrasse 95, D-72076 Tuebingen, Germany. Electronic address: fabian.stuby@uni-tuebingen.de. 2. BG Trauma Center, Eberhard Karls University, Schnarrenbergstrasse 95, D-72076 Tuebingen, Germany. Electronic address: sdoebele@bgu-tuebingen.de. 3. AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland. Electronic address: yash.agarwal@aofoundation.org. 4. AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland. Electronic address: markus.windolf@aofoundation.org. 5. AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland. Electronic address: boyko.gueorguiev@aofoundation.org. 6. BG Trauma Center, Eberhard Karls University, Schnarrenbergstrasse 95, D-72076 Tuebingen, Germany. Electronic address: gochs@bgu-tuebingen.de.
Abstract
BACKGROUND: Implant loosening is frequently detected after fixation of open book injuries. Though many authors do not see this as a complication, it is often the reason for hardware removal or reinstrumentation in the case of remaining instability. We hypothesized that the flexibility of the implant has an influence on loosening and thus on failure of the construct. METHODS: We used 6 fresh-frozen pelvic specimens and tested them with our recently introduced test setup for two-leg alternate loading. We subjected them to a non-destructive quasi-static test in the intact condition followed by a non-destructive cyclic test under axial sinusoidal loading with progressive amplitude. Afterwards we simulated an open book injury and performed fixation with three different configurations of a modular fixation system (1-, 2- or 4-rod configuration) in randomized order. Subsequently, the specimens were subjected to 3 cyclic tests with the same loading protocol as previously defined. Finally, each construct was cyclically tested to failure keeping the final rod configuration. FINDINGS: We detected significantly greater mobility after 1-rod-fixation and no significant differences after 2-rod or 4-rod-fixation compared to the intact symphysis condition. In the destructive test series the 4-rod-fixation failed first followed by the 1-rod-fixation. The 2-rod-fixation sustained almost 3 times as many load cycles prior to failure as the 4-rod-fixation, whereas the 1-rod-fixation sustained twice as many cycles as the 4-rod-fixation. INTERPRETATION: In conclusion, flexible fixation of the ruptured pubic symphysis in human specimens shows superior behavior with respect to load bearing capacity and ability to withstand cyclic loading compared to stiff constructs.
BACKGROUND: Implant loosening is frequently detected after fixation of open book injuries. Though many authors do not see this as a complication, it is often the reason for hardware removal or reinstrumentation in the case of remaining instability. We hypothesized that the flexibility of the implant has an influence on loosening and thus on failure of the construct. METHODS: We used 6 fresh-frozen pelvic specimens and tested them with our recently introduced test setup for two-leg alternate loading. We subjected them to a non-destructive quasi-static test in the intact condition followed by a non-destructive cyclic test under axial sinusoidal loading with progressive amplitude. Afterwards we simulated an open book injury and performed fixation with three different configurations of a modular fixation system (1-, 2- or 4-rod configuration) in randomized order. Subsequently, the specimens were subjected to 3 cyclic tests with the same loading protocol as previously defined. Finally, each construct was cyclically tested to failure keeping the final rod configuration. FINDINGS: We detected significantly greater mobility after 1-rod-fixation and no significant differences after 2-rod or 4-rod-fixation compared to the intact symphysis condition. In the destructive test series the 4-rod-fixation failed first followed by the 1-rod-fixation. The 2-rod-fixation sustained almost 3 times as many load cycles prior to failure as the 4-rod-fixation, whereas the 1-rod-fixation sustained twice as many cycles as the 4-rod-fixation. INTERPRETATION: In conclusion, flexible fixation of the ruptured pubic symphysis in human specimens shows superior behavior with respect to load bearing capacity and ability to withstand cyclic loading compared to stiff constructs.
Authors: Fabian M Stuby; Mark Lenz; Stefan Doebele; Yash Agarwal; Hristo Skulev; Björn G Ochs; Jörn Zwingmann; Boyko Gueorguiev Journal: PLoS One Date: 2017-11-27 Impact factor: 3.240
Authors: Martin C Jordan; Veronika Jäckle; Sebastian Scheidt; Fabian Gilbert; Stefanie Hölscher-Doht; Süleyman Ergün; Rainer H Meffert; Timo M Heintel Journal: Sci Rep Date: 2021-06-29 Impact factor: 4.379