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PurposeIn healthy humans, postural and respiratory dynamics are intimately linked and a breathing-related postural perturbation is evident in joint kinematics. A cognitive dual-task paradigm that is known to induce both postural and ventilatory disturbances can be used to modulate this multijoint posturo-ventilatory (PV) interaction, particularly in the cervical spine, which supports the head. The objective of this study was to assess this modulation.MethodsWith the use of optoelectronic sensors, the breathing profile, articular joint motions of the cervical spine, hip, knees and ankles, and centre of pressure (CoP) displacement were measured in 20 healthy subjects (37 years old [29; 49], 10 females) during natural breathing (NB), a cognitive dual task (COG), and eyes-closed and increased-tidal-volume conditions. The PV interaction in the CoP and joint motions were evaluated by calculating the respiratory emergence (REm).ResultsOnly the COG condition induced a decrease in the cervical REm (NB: 17.2% [7.8; 37.2]; COG: 4.2% [1.8; 10.0] p = 0.0020) concurrent with no changes in the cervical motion. The CoP REm (NB: 6.2% [3.8; 10.3]; COG: 12.9% [5.8; 20.7] p = 0.0696) and breathing frequency (NB: 16.6 min-1 [13.3; 18.7]; COG: 18.6 min-1 [16.3; 19.4] p = 0.0731) tended to increase, while the CoP (p = 0.0072) and lower joint motion displacements (p < 0.05) increased.ConclusionThis study shows stable cervical spine motion during a cognitive dual task, as well as increased postural perturbations globally and in other joints. The concurrent reduction in the PV interaction at the cervical spine suggests that this “stabilization strategy” is centrally controlled and is achieved by a reduction in the breathing-related postural perturbations at this level. Whether this strategy is a goal for maintaining balance remains to be studied.

Background Finite element modeling of the human head offers an alternative to experimental methods in understanding the biomechanical response of the head in trauma brain injuries. Falx, tentorium, and their notches are important structures surrounding the brain, and data about their anatomical variations are sparse. Objective To describe and quantify anatomical variations of falx cerebri, tentorium cerebelli, and their notches. Methods 3D reconstruction of falx and tentorium was performed by points identification on 40 brain CT-scans in a tailored Matlab program. A scatter plot was obtained for each subject, and 8 anatomical landmarks were selected. A reference frame was defined to determine the coordinates of landmarks. Segments and areas were computed. A reproducibility study was done. Results The height of falx was 34.9 ± 3.9 mm and its surface area 56.5 ± 7.7 cm 2 . The width of tentorium was 99.64 ± 4.79 mm and its surface area 57.6 ± 5.8 cm 2 . The mean length, height, and surface area of falx notch were respectively 96.9 ± 8 mm, 41.8 ± 5.9 mm, and 28.8 ± 5.8 cm 2 (range 15.8–40.5 cm 2 ). The anterior and maximal widths of tentorial notch were 25.5 ± 3.5 mm and 30.9 ± 2.5 mm; its length 54.9 ± 5.2 mm and its surface area 13.26 ± 1.6 cm 2 . The length of falx notch correlated with the length of tentorial notch ( r  = 0.62, P  < 0.05). Conclusion We observe large anatomical variations of falx, tentorium, and notches, crucial to better understand the biomechanics of brain injury, in personalized finite element models.

Better understanding of the effects of growth on children’s bones and cartilage is necessary for clinical and biomechanical purposes. The aim of this study is to define the 3D geometry of children’s rib cages: including sternum, ribs and costal cartilage. Three-dimensional reconstructions of 960 ribs, 518 costal cartilages and 113 sternebrae were performed on thoracic CT scans of 48 children, aged 4 months to 15 years. The geometry of the sternum was detailed and nine parameters were used to describe the ribs and rib cages. A “costal index” was defined as the ratio between cartilage length and whole rib length to evaluate the cartilage ratio for each rib level. For all children, the costal index decreased from rib level 1 to 3 and increased from level 3 to 7. For all levels, the cartilage accounted for 45–60 % of the rib length, and was longer for the first years of life. The mean costal index decreased by 21 % for subjects over 3-year old compared to those under three ( p  < 10 −4 ). The volume of the sternebrae was found to be highly age dependent. Such data could be useful to define the standard geometry of the pediatric thorax and help to detect clinical abnormalities.

Obstructive sleep apnea syndrome (OSAS) is associated with postural dysfunction characterized by abnormal spinal curvature and disturbance of balance and walking, whose pathophysiology is poorly understood. We hypothesized that it may be the result of a pathological interaction between postural and ventilatory functions. Twelve patients with OSAS (4 women, age 53 years [51-63] (median [quartiles]), apnea hypopnea index 31/h [24-41]) were compared with 12 healthy matched controls. Low dose biplanar X-rays (EOS® system) were acquired and personalized three-dimensional models of the spine and pelvis were reconstructed. We also estimated posturo-respiratory coupling by measurement of respiratory emergence, obtaining synchronized center of pressure data from a stabilometric platform and ventilation data recorded by an optico-electronic system of movement analysis. Compared with controls, OSAS patients, had cervical hyperextension with anterior projection of the head (angle OD-C7 12° [8; 14] vs. 5° [4; 8]; = 0.002), and thoracic hyperkyphosis (angle T1-T12 65° [51; 71] vs. 49° [42; 59]; = 0.039). Along the mediolateral axis: (1) center of pressure displacement was greater in OSAS patients, whose balance was poorer (19.2 mm [14.2; 31.5] vs. 8.5 [1.4; 17.8]; = 0.008); (2) respiratory emergence was greater in OSAS patients, who showed increased postural disturbance of respiratory origin (19.2% [9.9; 24.0] vs. 8.1% [6.4; 10.4]; = 0.028). These results are evidence for the centrally-mediated and primarily respiratory origin of the postural dysfunction in OSAS. It is characterized by an hyperextension of the cervical spine with a compensatory hyperkyphosis, and an alteration in posturo-respiratory coupling, apparently secondary to upper airway instability.

Predicting vehicle occupants’ posture during evasive manoeuvres is crucial for assessing their safety in the event of a collision. Volunteer experiments have been performed in the past under lateral accelerations, both within a vehicle cabin and on a seat mounted on a sled. However, discrepancies in the volunteer responses between both setups have been identified. This study hypothesizes that the response of the volunteers differs as a consequence of the proximity to the frame in the vehicle cabin, in comparison to the absence of such a structure on the sled. The present study conducted a novel sled experiment, on which five volunteers with anthropometry comparable to the 50th percentile male were subjected to 0.3 g lateral accelerations, with three different surrounding environments. In twelve pulses, an additional lateral structure was placed to the right or left side of the seated volunteers. The volunteers were asked to either brace or relax their muscles. The results show significant differences between the configurations with and without the structure placed on the right side. This effect was observed for both the lateral excursion of the upper body and the corresponding rotation when the volunteers were relaxed (p < 0.01). The average maximum lateral head rotation decreased from 27° to 14° with the structure on the right. No significant difference in head rotation was found for the braced muscle configuration. This study supports the hypothesis that the proximity to a surrounding environment influences human responses during dynamic loading. Nevertheless, there was no significant difference in maximum muscle activation between the configurations, but a faster reaction of the sternocleidomastoid muscle with the presence of the structure.

Well characterised mechanical response of the normal head-neck complex during passive motion is important to inform and verify physical surrogate and computational models of the human neck, and to inform normal baseline for clinical assessments. For 10 male and 10 female participants aged 20 to 29, the range of motion (ROM) of the neck about three anatomical axes was evaluated in active-seated, passive-lying and active-lying configurations, and the neck stiffness was evaluated in passive-lying. Electromyographic signals from the agonist muscles, normalised to maximum voluntary contractions, were used to provide feedback during passive motions. The effect of sex and configuration on ROM, and the effect of sex on linear estimates of stiffness in three regions of the moment–angle curve, were assessed with linear mixed models and generalised linear models. There were no differences in male and female ROM across all motion directions and configurations. Flexion and axial rotation ROM were configuration dependent. The passive-lying moment–angle relationship was typically non-linear, with higher stiffness (slope) closer to end of ROM. When normalising the passive moment–angle curve to active lying ROM, passive stiffness was sex dependent only for lateral bending region 1 and 2. Aggregate moment–angle corridors were similar for males and females in flexion and extension, but exhibited a higher degree of variation in applied moment for males in lateral bending and axial rotation. These data provide the passive response of the neck to low rate bending and axial rotation angular displacement, which may be useful for computational and surrogate modelling of the human neck.

Understanding of human neck stiffness and range of motion (ROM) with minimal neck muscle activation (“passive”) is important for clinical and bioengineering applications. The aim of this study was to develop, implement, and evaluate the reliability of methods for assessing passive-lying stiffness and ROM, in six head-neck rotation directions. Six participants completed two assessment sessions. To perform passive-lying tests, the participant’s head and torso were strapped to a bending (flexion, extension, lateral bending) or a rotation (axial rotation) apparatus, and clinical bed, respectively. The head and neck were manually rotated by the researcher to the participant’s maximum ROM, to assess passive-lying stiffness. Participant-initiated (“active”) head ROM was also assessed in the apparatus, and seated. Various measures of apparatus functionality were assessed. ROM was similar for all assessment configurations in each motion direction except flexion. In each direction, passive stiffness generally increased throughout neck rotation. Within-session reliability for stiffness (ICC > 0.656) and ROM (ICC > 0.872) was acceptable, but between-session reliability was low for some motion directions, probably due to intrinsic participant factors, participant-apparatus interaction, and the relatively low participant number. Moment-angle corridors from both assessment sessions were similar, suggesting that with greater sample size, these methods may be suitable for estimating population-level corridors.

Pathologies of the respiratory system can by accompanied by alterations of the biomechanical function of the rib cage, as well as of its morphology and movement. The assessment of such pathologies could benefit from rib cage kinematic analysis during breathing, but this analysis is challenging because of the difficulties in observing and quantifying bone movements in vivo. This work explored the feasibility of using biplanar x-rays to study rib cage modifications at different lung volumes and evaluated the potential of the method to characterize rib cage kinematic patterns in patients. Forty-seven asymptomatic adults and eleven obstructive sleep apnea syndrome (OSAS) patients underwent biplanar x-rays at three lung volumes: normal breathing, maximal and minimal volume. Rib cage and spinopelvic positional parameters were computed from 3D reconstruction of the skeleton. Results showed that inspiration mostly mobilized the ribs and costo-vertebral junction, while expiration was driven by the spine. OSAS patients had a different sagittal profile at rest than asymptomatic subjects, but these differences decreased at maximal and minimal volume. This suggests that patients employed different biomechanical strategies to attain a trunk configuration similar to asymptomatic subjects at minimal and maximal lung volume. This study confirmed that the proposed method could have an impact for the clinical assessment and understanding of pathologies involving breathing function, and which directly affect rib cage morphology. •Assessing the movement of the rib cage during breathing is still a challenge.•Biplanar x-ray was used to measure rib cage morphology at three lung volumes.•Different respiratory strategies were deployed by patients and healthy subjects.•The proposed method offers a novel approach to functional examination of rib cage.

The safety expectation is that ADTs will prevent crashes caused by human error. [...]there is the potential for great reductions in road traffic injuries, as human error is the primary cause of 94% of crashes (bit.ly/29kcWKA). [...]ADTs are expected to greatly change road traffic accident scenarios3 through (1) reductions in vehicle energy before a crash thanks to better braking designs, (2) the capability to prevent accidents by executing avoidance maneuvers, and (3) a better knowledge of vehicle surroundings and road infrastructure. [...]there is a risk that the safety systems designed for human-driven vehicles may be ineffective, or even injurious, in vehicles equipped with ADTs as automation of driving tasks increases. [...]the design of tomorrow's road safety technologies cannot be based on yesterday's accident scenarios.

Finite element modeling of the human head offers an alternative to experimental methods in understanding the biomechanical response of the head in trauma brain injuries. Falx, tentorium, and their notches are important structures surrounding the brain, and data about their anatomical variations are sparse. To describe and quantify anatomical variations of falx cerebri, tentorium cerebelli, and their notches.