A Novel Implant for Superior Pubic Ramus Fracture Fixation-Development and a Biomechanical Feasibility Study.

Background and Objectives: Pubic ramus fractures are common in compound pelvic injuries known to have an increased rate of morbidity and mortality along with recurrent and chronic pain, impeding a patient's quality of life. The current standard treatment of these fractures is percutaneous screw fixation due to its reduced risk of blood loss and shorter surgery times. However, this is an intricate surgical technique associated with high failure rates of up to 15%, related to implant failure and loss of reduction. Therefore, the aim of this biomechanical feasibility study was to develop and test a novel intramedullary splinting implant for fixation of superior pubic ramus fractures (SPRF), and to evaluate its biomechanical viability in comparison with established fixation methods using conventional partially or fully threaded cannulated screws. Materials and Methods: A type II superior pubic ramus fracture according to the Nakatani classification was created in 18 composite hemi-pelvises via a vertical osteotomy with an additional osteotomy in the inferior pubic ramus to isolate the testing of three SPRF fixation techniques performed in 6 semi-pelvises each using either (1) a novel ramus intramedullary splint, (2) a partially threaded ramus screw, or (3) a fully threaded ramus screw. Results: No significant differences were detected among the fixation techniques in terms of initial construct stiffness and number of cycles to failure, p ≥ 0.213. Conclusion: The novel ramus intramedullary splint can be used as an alternative option for treatment of pubic ramus fractures and has the potential to decrease the rate of implant failures due to its minimally invasive implantation procedure.

Biomechanical evaluation of an allograft fixation system for ACL reconstruction.

The purpose of this study was to compare the biomechanical stability, especially graft slippage of an allograft screw and a conventional interference screw for tibial implant fixation in ACL reconstruction. Twenty-four paired human proximal tibia specimens underwent ACL reconstruction, with the graft in one specimen of each pair fixed using the allograft screw and the other using the conventional interference screw. Specimens were subjected to cyclic tensile loading until failure. The two fixation methods did not show any statistical difference in load at graft slippage (p = 0.241) or estimated mean survival until slippage onset (p = 0.061). The ultimate load and the estimated mean survival until failure were higher for the interference screw (p = 0.04, and p = 0.018, respectively). Graft displacement at ultimate load reached values of up to 7.2 (interference screw) and 11.3 mm (allograft screw). The allograft screw for implant fixation in ACL reconstruction demonstrated comparable behavior in terms of graft slippage to the interference screw but underperformed in terms of ultimate load. However, the ultimate load, occurring at progressive graft slippage, may not be considered a direct indicator of clinical failure.

Biomechanical Assessment of Fracture Loads and Patterns of the Odontoid Process.

STUDY DESIGN: Laboratory study. OBJECTIVE: This study aimed to investigate the biomechanical competence and fracture characteristics of the odontoid process. SUMMARY OF BACKGROUND DATA: Odontoid fractures of the second cervical vertebra (C2) represent the most common spine fracture type in the elderly. However, very little is known about the underlying biomechanical fracture mechanisms. MATERIALS AND METHODS: A total of 42 C2 human anatomic specimens were scanned via computed tomography, divided in six groups, and subjected to combined quasistatic loading at -15°, 0°, and 15° in sagittal plane and -50° and 0° in transverse plane until fracturing. Bone mineral density (BMD), height, fusion state of the ossification centers, stiffness, yield load, and ultimate load were assessed. RESULTS: While lowest values for stiffness, yield load, and ultimate load were observed at load inclination of 15° in sagittal plane, no statistically significant differences were observed between the study groups ( P ≥0.235). BMD correlated positively with yield load ( r2 =0.350, P <0.001) and ultimate load ( r2 =0.955, P <0.001) but not with stiffness ( r2 =0.082, P =0.07). The specimens with clearly distinguishable fusion of the ossification centers revealed less data scattering of the biomechanical outcomes. CONCLUSION: Load direction plays a subordinate role in traumatic fractures of the odontoid process. BMD was associated with significant correlation to the biomechanical outcomes. Thus, odontoid fractures appear to result from of an interaction between the load magnitude and bone quality.

On Measuring Implant Fixation Stability in ACL Reconstruction.

Numerous methods and devices are available for implant fixation in anterior cruciate ligament (ACL) reconstruction. Biomechanical data indicate high variability in fixation stability across different devices. This study aims to provide a better insight into measuring the structural characteristics and mechanical behavior of ACL implant fixations. Fourteen human tibial specimens with reconstructed ACLs were subjected to progressively increasing dynamic loading until failure. The motions of the tibia, the proximal and distal graft ends, as well as the testing frame and actuator, were continuously recorded via a motion tracking system. Significantly higher displacements of the machine actuator (1.0 mm at graft slippage onset, and 12.2 mm at ultimate load) were measured compared to the displacements of the proximal (0.8 and 4.3 mm, respectively) and distal graft (0.1 and 3.4 mm, respectively) ends. The displacements measured at different sites showed significant correlations. The provided data suggest significant and systematic inaccuracies in the stiffness and slippage of the fixation when using machine displacement, as commonly reported in the literature. The assessment of the distal graft displacement excludes the artifactual graft elongation, and most accurately reflects the graft slippage onset indicating clinical failure. Considering the high displacement at the ultimate load, the ultimate load could be used as a standardized variable to compare different fixation methods. However, the ultimate load alone is not sufficient to qualitatively describe fixation stability.

A free cyanohydrin as arms and armour of Marasmius oreades.

Cyanogenic plants and fungi are widespread in nature. Although the origin of hydrocyanic acid in plants has been studied in detail, little is known about its origin in fungi. Here, we report the identification of the cyanohydrin of glyoxylic acid as the precursor of hydrocyanic acid in the fungus Marasmius oreades and several other cyanogenic fungi. Moreover, a feeding experiment revealed glycine as biosynthetic precursor of the cyanohydrin of glyoxylic acid. Thus, the cyanogenesis of M. oreades and other fungi is fundamentally different from cyanogenesis in plants.