title: Two-leg alternate loading model--a different approach to biomechanical investigations of fixation methods of the injured pelvic ring with focus on the pubic symphysis.
abstract: The dorsal component of the pelvic ring is considered to be the most essential element for the stability of the pelvic ring. None of the current biomechanical set-ups include the effect of shear stresses by alternating loads that the pelvic ring has to withstand during walking. We hypothesize that a biomechanical test set-up with two-leg alternate loading will lead to stress imitation at the pubic symphysis that are more similar to existing strains than other test set-ups, and would, therefore, be more adequate for biomechanical testing of fixation methods. A new biomechanical two-leg standing test set-up with an alternate pelvic loading was constructed and was validated with six human pelvises from fresh frozen cadavers. Three-dimensional motion tracking was performed. The specimens were subjected to a non-destructive quasi-static test and a non-destructive cyclic test with progressive load amplitude from 170 N to 340 N over 1000 cycles. The initial rotational 'range of motion' and 'mean displacement' around the vertical axis for a pre-load of 170 N was about 0.3° and 0.2°, respectively, increasing by 0.1-0.2° at a load of 340 N. The rotation around the vertical axis and the translation along the frontal horizontal axis confirmed the stability of the pubic symphysis. The rate of ascend of displacements decreased, once the rotation reached 1° or the translation reached 1mm. The current biomechanical test set-up was compared with previous clinical findings, and the method was found valid for measuring inter-segmentary movements at the pubic symphysis.
authors.affiliation: AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland. Electronic address: yash.agarwal@aofoundation.org.
authors.forename: Yash
authors.initials: Y
authors.lastname: Agarwal
authors.affiliation: Eberhard Karls University Tübingen, BG Trauma Center, Schnarrenbergstrasse 95, D-72076 Tuebingen, Germany. Electronic address: sdoebele@bgu-tuebingen.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Doebele
authors.affiliation: AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland. Electronic address: markus.windolf@aofoundation.org.
authors.forename: Markus
authors.initials: M
authors.lastname: Windolf
authors.affiliation: Ebrhard Karls University Tübingen, Institute of Clinical Anatomy, Elfriede-Aulhorn-Str. 8, D-72076 Tuebingen, Germany. Electronic address: thomas.shiozawa@uni-tuebingen.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Shiozawa
authors.affiliation: AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland. Electronic address: boyko.gueorguiev@aofoundation.org.
authors.forename: Boyko
authors.initials: B
authors.lastname: Gueorguiev
authors.affiliation: Eberhard Karls University Tübingen, BG Trauma Center, Schnarrenbergstrasse 95, D-72076 Tuebingen, Germany. Electronic address: fabian.stuby@uni-tuebingen.de.
authors.forename: Fabian M
authors.initials: FM
authors.lastname: Stuby
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D005593:Fracture Fixation, Internal; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D009068:Movement; D010384:Pelvic Bones / Q000502:physiology*; D011187:Posture; D011631:Pubic Symphysis / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D013314:Stress, Mechanical
keywords: Biomechanics; Human movement; Pelvic bone; Pubic symphysis