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Understanding the Fetal Journey
Published in Gowri Dorairajan, Management of Normal and High Risk Labour During Childbirth, 2022
Progressive flexion at the atlantooccipital joint occurs naturally. The fulcrum (atlantooccipital joint) is close to the short arm (head), given the spine as the rigid linear arm that must negotiate. So when the short arm (head) leads the journey, the short arm must flex or extend completely on this long arm (the fetal spine) to continue the journey through the curved cylinder (the pelvis). The atlantooccipital joint is placed more posteriorly on the head, so flexing the head will be more intelligent to reduce the total length of the spine. Flexing is also favoured as the cylinder is longer posteriorly and shorter anteriorly.
Bunny Suit
Published in R. Annie Gough, Injury Illustrated, 2020
The three of us resorted to manual labor. With hands on his head and our feet on the gurney, we pressed and pushed. With a crunch, we finally forced the last connection of bone to give way. The brain was examined, the dura was stripped, the pituitary was removed, and it was placed in the tissue storage jar. The coroner examined the base of the skull, feeling the smooth round opening with her gloved fingers. The joint where the skull meets the neck is called the Atlanto-Occipital joint, the AO. It is where C1, known as the atlas, the first cervical spine vertebra, articulates with the occipital bone of the skull base. The structure and function of the joint is best realized in nodding yes and no and in safely turning the head from side to side, protecting all the arteries in the neck that carry blood to the brain. This man had a wide AO joint; too wide. In fact, his AO had separated. By definition, his head came off his neck. This is a typical injury associated with motorcycle crashes, something a helmet will not protect against. Wildly dangerous to the spinal cord and brain stem, this injury was considered to be the cause of death.
Head and Neck
Published in Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno, Understanding Human Anatomy and Pathology, 2018
Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno
Internally, the occipital bone is marked by grooves for several dural sinuses: the sigmoid sinus (“S-shaped”), superior sagittal sinus, and the transverse sinuses. It also contains fossae for parts of the brain: the fossae for the cerebellum and the fossae for the occipital poles of the cerebral hemisphere (Plates 3.10 through 3.12). The atlanto-occipital joint is made by the occipital condyles and the superior articular facets of the atlas bone, which is part of the vertebral column (the atlas bone is named after Atlas, the mythical man who balanced the world on his shoulders, as the atlas balances the head on the neck). The atlas includes the anterior arch, superior articular facet, transverse process, and posterior arch (Plate 3.31b and c). Note that the transverse ligament of the atlas holds the dens to the anterior arch of the atlas. The retropharyngeal space is situated posterior to the cervical viscera and extends from the basilar part of the occipital bone to the superior mediastinum.
Impact of rest-break interventions on the neck and shoulder posture of symptomatic VDU operators during prolonged computer work
Published in International Journal of Occupational Safety and Ergonomics, 2018
Montakarn Chaikumarn, Nuttika Nakphet, Prawit Janwantanakul
The risk of developing MSDs related to posture resulted from an increased gravity-resisting moment with decreased CV angle [41]. Smaller CV angles indicate greater protraction of the head which means a forward head posture [42]. Increased flexion at the atlanto-occipital joint and also increased horizontal distance of the centre of mass of the head from its axis of rotation is a consequence of an increased extensor moment [43]. Straker et al. [41] also suggested that the increased neck flexion angle during working increased the moment around both the lower and upper cervical spine and led to increased stress on tissue and greater risk of developing MSDs.
A comparison of muscle activity, posture and body discomfort during the use of different computer screen sizes
Published in International Journal of Occupational Safety and Ergonomics, 2023
Praphatson Sengsoon, Kanruethai Siriworakunsak
This study showed that there was no significant change in the CVA after 0, 15, 30, 45 and 60 min of use of both computer screen sizes, and there was no significant difference between the use of 46.99 and 58.42-cm computer screen sizes. When using a computer with both screen sizes, it was determined that the CVA was not different perhaps because this study provided an ergonomic posture before starting the test. This posture may reduce forward head posture and neck flexion when using computers of both screen sizes. The CVA is related to neck pain and forward head posture [17]. Consistent with previous studies, it was determined that there was no change in the CVA in computer workers with a neck health condition [18]. In this study, the level of the chair seats, footrests, armrest angles and computer screen viewing angles were determined. The participants were in an ergonomic position from the start of the test. However, prolonged sitting may result in thoracic flexion. In this study, the body was more likely in the neck extension position than in the neck flexion position, which caused the CVA not to change. This result is consistent with a previous study [19]. It was determined that the adolescent CVA did not change in function to maintain posture. Previous studies also showed that the minimal level of detectable change of CVA at 3.61° was a risk factor for neck pain [20]. In this study, the use of a 46.99-cm computer screen resulted in a minimum and maximum CVA of 31.92 and 33.92, respectively, while the use of a 58.42-cm computer screen resulted in a minimum and maximum CVA of 32.46 and 34.47, respectively. The difference was equal to 2° and 2.01°, respectively. Therefore, it was determined that both computer screen sizes can prevent the risk of neck pain problems. In this study, the CVA for the use of both computer screens were not significantly different. This may be due to the front visual eye field. Normal people have a visual eye field of 180° [21]. The ergonomic distance between the eyes and computer screen at 40.64–76.20 cm is an ideal angle to reduce the risk of injury [22]. Of note, this is sufficient to view both computer screens. The neck angle did not change during the neck postural control; thus, there was a small change in the CCA only according to the cervical biomechanics principle, and the neck movement first occurred in the upper cervical region. Moreover, movement of the neck at a small angle was found to be associated with the head nodding movement in the atlanto-occipital joint and associated with CCA [23,24].