Biomechanical analysis of cervical spine (C2-C7) at different flexed postures.

Musculoskeletal diseases are often related with postural changes in the neck region that can be caused by prolonged cervical flexion. This is one of the contributing factors. When determining the prevalence, causes, and related risks of neck discomfort, having a solid understanding of the biomechanics of the cervical spine (C1-C7) is absolutely necessary. The objective of this study is to make predictions regarding the intervertebral disc (IVD) stress values across C2-C7 IVD, the ligament stress, and the variation at 0°, 15°, 30°, 45°, and 60° of cervical neck angle using finite element analysis (FEA). In order to evaluate the mechanical properties of the cervical spine (particularly, C2-C7), this investigation makes use of computed tomography (CT) scans to develop a three-dimensional FEA model of the cervical spine. A preload of 50 N compression force was applied at the apex of the C2 vertebra, and all degrees of freedom below the C7 level were constrained. The primary objective of this investigation is to assess the distribution of von Mises stress within the IVDs and ligaments spanning C2-C7 at various flexion angles: 0°, 15°, 30°, 45°, and 60°, utilizing FEA. The outcomes derived from this analysis were subsequently compared to previously published experimental and FEA data to validate the model's ability to replicate the physiological motion of the cervical spine across different flexion angles.

Ergonomic evaluation of upper extremities muscle activity pattern during 60-min smartphone texting.

BACKGROUND: Smartphone usage has increased rapidly in the last decade due to rapid technological advancements. This extensive usage of smartphones led to physiological problems and musculoskeletal disorders (MSD) due to inappropriate postures. OBJECTIVE: Past studies have reported the effects/discomfort of smartphone usage for short periods, ranging from 3-20 min, which does not represent the current era of smartphone dependency (approximately 7-hr/day). METHODS: This study was performed on fifty-four participants aged 20-28 with 1-hr smartphone texting in a sitting posture. Flexion angles, both sides (dominant and non-dominant) muscle activity (maximum voluntary contraction %) at sternocleidomastoid (SCM), upper-trapezius (TRP), extensor digitorum (EDM) and abductor pollicis brevis (APB) muscles, and subjective discomfort were analyzed. RESULTS: After 1-hr smartphone texting, the muscle activity at eight upper extremities: SCM (24.80%), TRP (29.45%), EDM (14.44%) and APB (19.87%) significantly (p <  0.001) increased by 1.5-1.9 times with 27.4±3.18° and 82.94±7.03° head and lower-arm flexion angles, respectively. The mechanical loads on the cervical spine increased by 4.6 times, and subjective discomfort by 3 times. CONCLUSION: Maintaining the same posture for a long duration causes postural stress, muscular imbalances, and discomfort, leading to MSD with increased cervical intervertebral disc pressure.

Influence of smartphone game play on head flexion angle, muscle activity, and load at C7 among adolescents.

BACKGROUND: Smartphones cause physiological problems due to inappropriate postures and extensive usage. India, being the second leading country with the highest number of smartphone users (492 million in 2021), has witnessed a significant rise in smartphone-related musculoskeletal disorders (MSD). OBJECTIVE: This study compared the effects of 60-min smartphone gameplay on head flexion angle, muscle activity, and loads at C7 on Indian adolescents. METHODS: A subjective assessment was conducted on 1659 participants, of which, 40 young male adults aged between 20-28 years performed the experimental trial. Muscle (Sternocleidomastoid) activity, head flexion angle, and load acting at the neck (C7) were analyzed through postural assessment, pre-and post-subjective analysis. RESULTS: Participants maintained an average of 28.46°±4.04° head flexion angle for more than 43 min (71%) in an hour while performing the task. The muscle activity increased to 23% (p < 0.001) of MVC at the end of the task compared to the beginning. CONCLUSION: The results indicated a significant increase in muscle activity (1.61 times), spinal loads (4.6 times) and subjective discomfort (2.9 times) after prolonged smartphone usage. It is evident that various aspects (duration, posture, content) play a vital role in smartphone-related MSD and there is a potential risk of cervical spine problems. The increased loads reduce muscle stiffness and increase intervertebral disc pressure.