The complexity of the osseo-ligamentous lumbopelvic system has made it difficult to perform both, the overall preparation as well as specimen harvesting and material testing with a reasonable amount of time and personnel. The logistics of such studies present a hurdle for reproducibility. A structured procedure was developed and proved, which allows all necessary steps to be carried out reproducibly and in a reasonable time. This enables the extraction of 26 soft tissue, 33 trabecular and 32 cortical bone specimens from this anatomical region per cadaver. The integrity of the specimens remains maintained while keeping requirements within manageable limits. The practicability of the intended five-day specimen harvesting and testing procedure could be demonstrated on five test and two pre-test sequences. The intended minimization of physical, biological, and chemical external influences on specimens could be achieved. All protocols, instructions and models of preparation and storage devices are included in the supporting information. The high grade of applicability and reproducibility will lead to better comparability between different biomechanical investigations. This procedure proven on the human pelvis is transferable to other anatomical regions.
Pedicle screw fixation is a common spinal surgery technique, but concerns remain about stability when screws are malpositioned. Traditional in vitro pull-out tests assess anchorage but lack physiological accuracy. This study examined the stability of correctly placed and intentionally malpositioned pedicle screws on forty vertebrae from five cadavers. Optimal screw paths were planned via CT scans and applied using 3D-printed guides. Four malposition types—medial, lateral, superior, and superior-lateral—were created by shifting the original trajectory. A custom setup applied three consecutive cycles of tensile and compressive load from 50 N to 200 N. Screw inclination under load was measured with a 3D optical system. The results showed increasing screw inclination with higher forces, reaching about 1° at 50 N and 2° at 100 N, similar in both load directions. Significant differences in inclination were only found at 100 N tensile load, where malpositioned screws showed a lower inclination. Overall, malpositioning had no major effect on screw loosening. These findings suggest that minor deviations in screw placement do not significantly compromise mechanical stability. Clinically, the main concern with malpositioning lies in the potential for injury to nearby structures rather than reduced screw fixation strength.
The osseo-ligamentous lumbopelvic complex is essential for musculoskeletal load transfer, yet location-specific material data and standardized test protocols remain scarce, which is a hindrance for comparability. Based on 91 specimen locations per cadaver (five cadavers, average age: 77.3 years), we developed detailed methods for specimen preparation and mechanical testing (bending, tensile, and compression) with defined boundary conditions. Multiple measurements were taken to assess repeatability. The proposed methods allow us to identify location-specific properties of the lumbopelvic system for the first time. Cortical bone exhibited an elastic modulus of 1750 MPa and an ultimate strength of 28.2 MPa, while those of trabecular bone were 32.7 MPa and 1.26 MPa, and soft tissues revealed values of 148 MPa and 14.3 MPa for fascial tissue and 103 MPa with 10.7 MPa for ligamentous tissue, respectively. The quantified properties for cortical and trabecular bone and soft tissues not only enhance the comparability of material properties but also support more accurate numerical simulations and implant design. Furthermore, the ease of implementation and standardization of these methods enable their widespread application, as well as the accumulation of a broad database and the setting of benchmarks for future investigations.