Influence of bending pre-load on the tensile response of the lumbar spine

Previous full body cadaver testing has shown that both obliquely oriented seats in survivable aircraft crashes and far-side oblique crashes in vehicles present distinctive occupant kinematics that are not yet well understood. Knowledge surrounding how these loading scenarios affect the lumbar spine is particularly lacking as there exists minimal research concerning oblique loading. The current study was created to evaluate a novel experimental method through comparison with existing literature, and to examine the impact of a static bending pre-load (posture) on the load-displacement response for the whole lumbar spine loaded in non-destructive axial distraction. T12-S1 lumbar spines were tested in tension to 4 mm of displacement while positioned in one of three pre-load postures. These postures were: the spine's natural, unloaded curvature (neutral), flexed forward (flexed), and combined flexion and lateral bending (oblique). Deviations from a neutral spine position were shown to significantly increase peak loads and tensile stiffness. The presence of a flexion pre-load caused statistically significant increases in tensile stiffness, tensile force, and bending moments. The addition of a lateral bending pre-load to an already flexed spine did not significantly alter the tensile response. However, the flexion moment response was significantly affected by the additional postural pre-load. This work indicates that the initial conditions of distraction loading significantly affect lumbar spine load response. Therefore, future testing that seeks to emulate crash dynamics of obliquely seated occupants must account for multi-axis loading.

Occupant Injury and Response On Oblique-Facing Aircraft Seats: A Computational Study

Increased interest in the airline industry to enhance occupant comfort and maximize seating density has prompted the design and installation of obliquely mounted seats in aircraft. Previous oblique whole-body sled tests demonstrated multiple failures, chiefly distraction-associated spinal injuries under oblique impacts. The present computational study was performed with the rationale to examine how oblique loading induces component level responses and associated injury occurrence. The age-specific human body model (HBM) was simulated for two oblique seating conditions (with / without an armrest). The boundary conditions consisted of a 16g standard aviation crash pulse, 45° seat orientation, and with restrained pelvis and lower extremities. The overall biofidelity rating for both conditions ranged from 0.5 to 0.7. The validated models were then used to investigate the influence of pulse intensity and seat orientation by varying the pulse from 16 to 8g and seat orientation from 0° to 90°. A total of 12 parametric simulations were performed. The pulse intensity simulations suggest that the HBM could tolerate 11.2g without lumbar spine failure, while the possibility of cervical spine failure reduced with the pulse magnitude <9.6g pulse. The seat orientation study demonstrated that for all seat angles the HBM predicted failure in the cervical and lumbar regions at 16g; however, the contribution of the tensile load and lateral, and flexion moments varied with respect to the change in seat angle. These preliminary outcomes are anticipated to assist in formulating safety standards and in designing countermeasures for oblique seating configurations.

Injuries to Post Mortem Human Surrogates in Oblique Aircraft Seat Environment

Increased interest in the airline industry to enhance occupant comfort and maximize seating density has prompted the design and installation of obliquely mounted seats in aircraft. The potential for injury and their mechanism in this seating environment is unknown. Epidemiology-based field injury data do not exist for airplane crashes, however, typical impact scenarios have been determined and safety standards addressing fore, aft, and side-facing seats have been levied by the FAA. The impact scenarios defined in these standards can be used to study likely injuries and injury mechanisms using Post Mortem Human Surrogates (PMHS) in a controlled laboratory environment. Four PMHS were seated upright with Frankfurt plane horizontal in a custom designed seat configured to simulate potential aircraft environments and candidate restraint geometries. A scaled Part 25.562 Emergency Landing condition for horizontal impact was used as the dynamic test input. High speed video recorded occupant kinematics. Pre and posttest x-rays and CT’s were obtained and autopsies were conducted. Severe injuries to the cervical, thoracic, and lumbar spine were observed in three of the four specimens and attributed to torso flail. Pelvis injuries likely caused by the seat belt were found in two tests. Multiple rib fractures were also seen, caused by contact with arm rest or other body regions. The fourth test was run at a lower severity and did not produce injury. This suggests a conservative threshold for human tolerance to this loading environment. Although the study is of a limited sample size, it suggests the need for further testing to develop standards that provide similar levels of safety for obliquely mounted seats as forward/aft facing seats in aircraft.

Investigation of the THOR Anthropomorphic Test Device for Predicting Occupant Injuries during Spacecraft Launch Aborts and Landing

The objective of this study was to investigate new methods for predicting injury from expected spaceflight dynamic loads by leveraging a broader range of available information in injury biomechanics. Although all spacecraft designs were considered, the primary focus was the National Aeronautics and Space Administration Orion capsule, as the authors have the most knowledge and experience related to this design. The team defined a list of critical injuries and selected the THOR anthropomorphic test device as the basis for new standards and requirements. In addition, the team down-selected the list of available injury metrics to the following: head injury criteria 15, kinematic brain rotational injury criteria, neck axial tension and compression force, maximum chest deflection, lateral shoulder force and displacement, acetabular lateral force, thoracic spine axial compression force, ankle moments, and average distal forearm speed limits. The team felt that these metrics capture all of the injuries that might be expected by a seated crewmember during vehicle aborts and landings. Using previously determined injury risk levels for nominal and off-nominal landings, appropriate injury assessment reference values (IARVs) were defined for each metric. Musculoskeletal deconditioning due to exposure to reduced gravity over time can affect injury risk during landing; therefore a deconditioning factor was applied to all IARVs. Although there are appropriate injury data for each anatomical region of interest, additional research is needed for several metrics to improve the confidence score.

The role of wavelength and source in the search for sulfur-atom positions evaluated in two case studies: lysozyme at room temperature and cryo apocrustacyanin A1

Synchrotron radiation beamlines offer automated data collection with faster and larger detectors, a choice of wavelength(s), intense beams and fine collimation. An increasing output of protein crystal structures sustains an interest in streamlining data collection protocols. Thus, more and more investigators are looking into the use of the anomalous signal from sulfur to obtain initial phase information for medium-size proteins. This type of experiment ideally requires the use of synchrotron radiation, softer X-rays and cryocooling of the sample. Here the results are reported of an investigation into locating the weak,i.e.sulfur, anomalous scatterers in lysozyme using rotating anode or synchrotron radiation data recorded at room temperature. It was indeed possible to locate the sulfur atoms from a lysozyme crystal at room temperature. Accurate selection of images during scaling was needed where radiation damage effects were detected. Most interestingly, comparisons are provided of high-redundancy data sets recorded with synchrotron radiation at λ = 2.0 and 1.488 Å, and with CuKα and MoKα radiation. Apocrustacyanin A1 was also investigated; from the results of a very high redundancy data collection using softer synchrotron X-rays and a cryo-cooled crystal, it was possible to find the sulfur atoms.

Secondary structures of hyaluronate and chondroitin sulphates. A 1H n.m.r. study of NH signals in dimethyl sulphoxide solution

1H n.m.r. spectra in [2H6]dimethyl sulphoxide of dodecyltrimethylammonium salts of chondroitin sulphates and hyaluronate, or sodium salts of oligomers from hyaluronate, showed unambiguous NH signals. The acetamido NH occurs in two different environments: environment I ('normal') in simple sugars, and environment II (hydrogen-bonded NH) appearing in tri- or tetrasaccharides, indicating a secondary structure in hyaluronate (and some chondroitin sulphates) involving a hydrogen-bonded acetamido NH.