Investigating the effect of anatomical variations in the response of the neonatal brachial plexus to applied force: Use of a two-dimensional finite element model.

The brachial plexus is a set of nerves that innervate the upper extremity and may become injured during the birthing process through an injury known as Neonatal Brachial Plexus Palsy. Studying the mechanisms of these injuries on infant cadavers is challenging due to the justifiable sensitivity surrounding testing. Thus, these specimens are generally unavailable to be used to investigate variations in brachial plexus injury mechanisms. Finite Element Models are an alternative way to investigate the response of the neonatal brachial plexus to loading. Finite Element Models allow a virtual representation of the neonatal brachial plexus to be developed and analyzed with dimensions and mechanical properties determined from experimental studies. Using ABAQUS software, a two-dimensional brachial plexus model was created to analyze how stresses and strains develop within the brachial plexus. The main objectives of this study were (1) to develop a model of the brachial plexus and validate it against previous literature, and (2) to analyze the effect of stress on the nerve roots based on variations in the angles between the nerve roots and the spinal cord. The predicted stress for C5 and C6 was calculated as 0.246 MPa and 0.250 MPa, respectively. C5 and C6 nerve roots experience the highest stress and the largest displacement in comparison to the lower nerve roots, which correlates with clinical patterns of injury. Even small (+/- 3 and 6 degrees) variations in nerve root angle significantly impacted the stress at the proximal nerve root. This model is the first step towards developing a complete three-dimensional model of the neonatal brachial plexus to provide the opportunity to more accurately assess the effect of the birth process on the stretch within the brachial plexus and the impact of biological variations in structure and properties on the risk of Neonatal Brachial Plexus Palsy.

Simulation of Uterus Active Contraction and Fetus Delivery in ls-dyna.

Vaginal childbirth is the final phase of pregnancy when one or more fetuses pass through the birth canal from the uterus, and it is a biomechanical process. The uterine active contraction, causing the pushing force on the fetus, plays a vital role in regulating the fetus delivery process. In this project, the active contraction behaviors of muscle tissue were first modeled and investigated. After that, a finite element method (FEM) model to simulate the uterine cyclic active contraction and delivery of a fetus was developed in ls-dyna. The active contraction was driven through contractile fibers modeled as one-dimensional truss elements, with the Hill material model governing their response. Fibers were assembled in the longitudinal, circumferential, and normal (transverse) directions to correspond to tissue microstructure, and they were divided into seven regions to represent the strong anisotropy of the fiber distribution and activity within the uterus. The passive portion of the uterine tissue was modeled with a Neo Hookean hyperelastic material model. Three active contraction cycles were modeled. The cyclic uterine active contraction behaviors were analyzed. Finally, the fetus delivery through the uterus was simulated. The model of the uterine active contraction presented in this paper modeled the contractile fibers in three-dimensions, considered the anisotropy of the fiber distribution, provided the uterine cyclic active contraction and propagation of the contraction waves, performed a large deformation, and caused the pushing effect on the fetus. This model will be combined with a model of pelvic structures so that a complete system simulating the second stage of the delivery process of a fetus can be established.

Simulation of the Childbirth Process in LS-DYNA.

Childbirth or labor, as the final phase of a pregnancy, is a biomechanical process that delivers the fetus from the uterus. It mainly involves two important biological structures in the mother, the uterus-generating the pushing force on the fetus-and the pelvis (bony pelvis and pelvic floor muscles)-resisting the movement of the fetus. The existing computational models developed in this field that simulate the childbirth process have focused on either the uterine expulsion force or the resistive structures of the pelvis, not both. An FEM model including both structures as a system was developed in this paper to simulate the fetus delivery process in LS-DYNA. Uterine active contraction was driven by contractile fiber elements using the Hill material model. The passive portion of the uterus and pelvic floor muscles were modeled with Neo Hookean and Mooney-Rivlin materials, respectively. The bony pelvis was modeled as a rigid body. The fetus was divided into three components: the head, neck, and body. Three uterine active contraction cycles were modeled. The model system was validated based on multiple outputs from the model, including the stress distribution within the uterus, the maximum Von Mises and principal stress on the pelvic floor muscles, the duration of the second stage of the labor, and the movement of the fetus. The developed model system can be applied to investigate the effects of pathomechanics related to labor, such as pelvic floor disorders and brachial plexus injury.

Studying the Effects of Shoulder Dystocia and Neonate-Focused Delivery Maneuvers on Brachial Plexus Strain: A Computational Study.

The purpose of this computational study was to investigate the effects of neonate-focused clinical delivery maneuvers on brachial plexus (BP) during shoulder dystocia. During shoulder dystocia, the anterior shoulder of the neonate is obstructed behind the symphysis pubis of the maternal pelvis, postdelivery of the neonate's head. This is managed by a series of clinical delivery maneuvers. The goal of this study was to simulate these delivery maneuvers and study their effects on neonatal BP strain. Using madymo models of a maternal pelvis and a 90th-percentile neonate, various delivery maneuvers and positions were simulated including the lithotomy position alone of the maternal pelvis, delivery with the application of various suprapubic pressures (SPPs), neonate in an oblique position, and during posterior arm delivery maneuver. The resulting BP strain (%) along with the required maternal delivery force was reported in these independently simulated scenarios. The lithotomy position alone served as the baseline. Each of the successive maneuvers reported a decrease in the required delivery force and resulting neonatal BP strain. As the applied SPP force increased (three scenarios simulated), the required maternal delivery force and neonatal BP strain decreased. A further decrease in both delivery force and neonatal BP strain was observed in the oblique position, with the lowest delivery force and neonatal BP strain reported during the posterior arm delivery maneuver. Data obtained from the improved computational models in this study enhance our understanding of the effects of clinical maneuvers on neonatal BP strain during complicated birthing scenarios such as shoulder dystocia.

How to Build Your Mentoring Tree-Insight Gained From a 36-Year Career in Biomedical Engineering.

Mentoring is often viewed as a unidirectional relationship, with the senior, more seasoned individual imparting knowledge, guidance, and experience to more junior individuals. But this structure limits our ability to recognize that the mentoring relationship can bring benefits and opportunities for growth to the mentor as well. On the occasion of receiving the 2022 Robert M. Nerem Education and Mentorship Medal, I have had the opportunity to reflect on the mentoring that I have been lucky enough to participate in-both as mentor and mentee-during my academic career. This paper discusses some of those insights and presents the concept of a mentoring tree-through which we can identify multiple mentors and mentees, each of whom can provide mutual support and insight as we progress through our careers. Each individual who is part of our mentoring tree can play a role at different times and with different challenges within our professional path. This everchanging and growing structure provides continuous mentoring without overtaxing any single relationship.

A Computational Procedure to Derive the Curve of Carus for Childbirth Computational Modeling.

Computational modeling serves an important role in childbirth-related research. Prescribed fetal descent trajectory is a key characteristic in childbirth simulations. Two major types of fully prescribed fetal descent trajectories can be identified in the literature: straight descent trajectories and curve of Carus. The straight descent trajectory has the advantage of being simpler and can serve as a reasonable approximation for relatively small fetal movements during labor, but it cannot be used to simulate the entire childbirth process. The curve of Carus is the well-recognized fetal descent trajectory with physiological significance. However, no detailed procedure to geometrically define the curve of Carus can be found in existing computational studies. This status of curve of Carus simulation in the literature hinders the direct comparison of results across different studies and the advancement of computational techniques built upon previous research. The goals of this study are: (1) propose a universal approach to derive the curve of Carus for the second stage of labor, from the point when the fetal head engages the pelvis to the point when the fetal head is fully delivered; and (2) demonstrate its utility when considering various fetal head sizes. The current study provides a detailed formulation of the curve of Carus, considering geometries of both the mother and the fetus. The maternal geometries were obtained from MRI data, and the fetal head geometries were based on laser scanning of a replica of a real fetal head.

Smart Steering Sleeve (S3): A Non-Intrusive and Integrative Sensing Platform for Driver Physiological Monitoring.

Driving is a ubiquitous activity that requires both motor skills and cognitive focus. These aspects become more problematic for some seniors, who have underlining medical conditions and tend to lose some of these capabilities. Therefore, driving can be used as a controlled environment for the frequent, non-intrusive monitoring of bio-physical and cognitive status within drivers. Such information can then be utilized for enhanced assistive vehicle controls and/or driver health monitoring. In this paper, we present a novel multi-modal smart steering sleeve (S3) system with an integrated sensing platform that can non-intrusively and continuously measure a driver's physiological signals, including electrodermal activity (EDA), electromyography (EMG), and hand pressure. The sensor suite was developed by combining low-cost interdigitated electrodes with a piezoresistive force sensor on a single, flexible polymer substrate. Comprehensive characterizations on the sensing modalities were performed with promising results demonstrated. The sweat-sensing unit (SSU) for EDA monitoring works under a 100 Hz alternative current (AC) source. The EMG signal acquired by the EMG-sensing unit (EMGSU) was amplified to within 5 V. The force-sensing unit (FSU) for hand pressure detection has a range of 25 N. This flexible sensor was mounted on an off-the-shelf steering wheel sleeve, making it an add-on system that can be installed on any existing vehicles for convenient and wide-coverage driver monitoring. A cloud-based communication scheme was developed for the ease of data collection and analysis. Sensing platform development, performance, and limitations, as well as other potential applications, are discussed in detail in this paper.

Learning Environments and Evidence-Based Practices in Bioengineering and Biomedical Engineering.

This paper provides a synopsis of discussions related to the Learning Environments track of the Fourth BME Education Summit held at Case Western Reserve University in Cleveland, Ohio in May 2019. This summit was organized by the Council of Chairs of Bioengineering and Biomedical Engineering, and participants included over 300 faculty members from 100+ accredited undergraduate programs. The Learning Environments track had six interactive workshops that provided facilitated discussion and provide recommendations in the areas of: (1) Authentic project/problem identification in clinical, industrial, and global settings, (2) Experiential problem/project-based learning within courses, (3) Experiential learning in co-curricular learning settings, (4) Team-based learning, (5) Teaching to reach a diverse classroom, and (6) innovative platforms and pedagogy. A summary of the findings, best practices and recommendations from each of the workshops is provided under separate headings below, and a list of resources is provided at the end of this paper.

Interactive Digital Experience as an Alternative Laboratory (IDEAL): Creative Investigation of Forensic Biomechanics.

An Interactive Digital Experience as an Alternative Laboratory (IDEAL) was developed and implemented in a flipped biomechanics classroom. The IDEAL challenge problem was created to more closely simulate a real-world scenario than typical homework or challenge problems. It added a more involved story, specific characters, simple interaction, and student-led inquiry into a challenge problem. Students analyzed musculoskeletal biomechanics data to conduct a forensic biomechanics investigation of an individual who suffered a fracture. Students ultimately approached the IDEAL problem with a greater appreciation and enjoyment than previous open-ended challenge problems-those that were assigned in a traditional problem-statement manner-throughout the semester. Students who were more fully engaged in the IDEAL challenge problem, as evidenced by the fact that they requested all of the evidence on their own, also performed better on the final report grade. This signals improved learning with respect to biomechanical analysis when the students were creatively participating in the storyline surrounding the forensic investigation.

Forces Involved with Labor and Delivery-A Biomechanical Perspective.

Childbirth is a primarily biomechanical process of physiology, and one that engineers have recently begun to address in a broader fashion. Computational models are being developed to address the biomechanical effects of parturition on both maternal and fetal tissues. Experimental research is being conducted to understand how maternal tissues adapt to intrauterine forces near the onset of labor. All of this research requires an understanding of the forces that are developed through maternal efforts-both uterine contractions and semi-voluntary pushing-and that can be applied by the clinician to assist with the delivery. This work reviews the current state of knowledge regarding forces of labor and delivery, with a focus on macro-level biomechanics.

Childbirth Computational Models: Characteristics and Applications.

The biomechanical process of childbirth is necessary to usher in new lives-but it can also result in trauma. This physically intense process can put both the mother and the child at risk of injuries and complications that have life-long impact. Computational models, as a powerful tool to simulate and explore complex phenomena, have been used to improve our understanding of childbirth processes and related injuries since the 1990s. The goal of this paper is to review and summarize the breadth and current state of the computational models of childbirth in the literature-focusing on those that investigate the mechanical process and effects. We first summarize the state of critical characteristics that have been included in computational models of childbirth (i.e., maternal anatomy, fetal anatomy, cardinal movements, and maternal soft tissue mechanical behavior). We then delve into the findings of the past studies of birth processes and mechanical injuries in an effort to bridge the gap between the theoretical, numerical assessment and the empirical, clinical observations and practices. These findings are from applications of childbirth computational models in four areas: (1) the process of childbirth itself, (2) maternal injuries, (3) fetal injuries, and (4) protective measures employed by clinicians during delivery. Finally, we identify some of the challenges that computational models still face and suggest future directions through which more biofidelic simulations of childbirth might be achieved, with the goal that advancing models may provide more efficient and accurate, patient-specific assessment to support future clinical decision-making.

Design as a Feature of Biomedical Engineering Education-Satisfying ABET and Preparing Students to Address Clinical Needs.

Design is an important aspect of biomedical engineering education. It prepares students to work as part of a team to develop systems that address medical and health-related needs-and it is required to be part of an accredited undergraduate engineering program. This work looks at the history of design requirements in the U.S. and the current state of biomedical engineering curricula with respect to design. As a growing number of programs have expanded their design program beyond the capstone project, some examples of innovative programs are described. There is no single way to address design education within an undergraduate biomedical engineering program. However, intentional development of this component of the curriculum can enhance the impact on student learning and outcomes.

Herbert R. Lissner: The Father of Impact Biomechanics.

Professor Herbert R. Lissner was a pioneer in impact biomechanics, having initiated research on the injury mechanisms, mechanical response, and human tolerance of the human brain to blunt impact 80 years ago-in 1939. This paper summarizes the contributions made by Professor Lissner in head injury as well as in the many areas of impact biomechanics in which he was involved. In 1977, the Bioengineering Division of ASME established the H. R. Lissner Award to recognize outstanding career achievements in the area of biomechanics. In 1987, this award was converted to a society-wide Medal, and to date it has been awarded to 44 exemplary researchers and educators. The lead author of this paper was Professor Lissner's first and only Ph.D. student, and he offers a unique insight into his research and contributions.

Engineering and women's health: a slow start, but gaining momentum.

While biomedical engineers have participated in research studies that focus on understanding aspects particular to women's health since the 1950s, the depth and breadth of the research have increased significantly in the last 15-20 years. It has been increasingly clear that engineers can lend important knowledge and analysis to address questions that are key to understanding physiology and pathophysiology related to women's health. This historical survey identifies some of the earliest contributions of engineers to exploring aspects of women's health, from the behaviour of key tissues, to issues of reproduction and breast cancer. In addition, some of the more recent work in each area is identified and areas deserving additional attention are described. The interdisciplinary nature of this area of engineering, along with the growing interest within the field of biomedical engineering, promise to bring exciting new discoveries and expand knowledge that will positively impact women's health in the near future.

Maternal Endogenous Forces and Shoulder Dystocia.

Childbirth is a complicated biomechanical process that many take for granted. However, the delivery forces generated by a mother (uterine contractions and maternal pushing) are strong and have a significant effect on the body and tissues of the fetus, especially during the second stage of labor. Although most infants are born without negative, force-related outcomes, in some infants the normal forces of labor cause an injury that can have either temporary or permanent sequelae. The biomechanical situation is further complicated when an infant's shoulder impacts the maternal pelvis, which provides increased resistance and creates added stresses within the neonatal body and tissues.

Transcranial sonothrombolysis using high-intensity focused ultrasound: impact of increasing output power on clot fragmentation.

BACKGROUND: The primary goal of this study was to investigate the relationship between increasing output power levels and clot fragmentation during high-intensity focused ultrasound (HIFU)-induced thrombolysis. METHODS: A HIFU headsystem, designed for brain applications in humans, was used for this project. A human calvarium was mounted inside the water-filled hemispheric transducer. Artificial thrombi were placed inside the skull and located at the natural focus point of the transducer. Clots were exposed to a range of acoustic output power levels from 0 to 400 W. The other HIFU operating parameters remained constant. To assess clot fragmentation, three filters of different mesh pore sizes were used. To assess sonothrombolysis efficacy, the clot weight loss was measured. RESULTS: No evidence of increasing clot fragmentation was found with increasing acoustic intensities in the majority of the study groups of less than 400 W. Increasing clot lysis could be observed with increasing acoustic output powers. CONCLUSION: Transcranial sonothrombolysis could be achieved in vitro within seconds in the absence of tPA and without producing relevant clot fragmentation, using acoustic output powers of <400 W.

Effect of clinician-applied maneuvers on brachial plexus stretch during a shoulder dystocia event: investigation using a computer simulation model.

OBJECTIVE: The objective of the study was to determine how standard shoulder dystocia maneuvers affect delivery force and brachial plexus stretch. STUDY DESIGN: A 3-dimensional computer model of shoulder dystocia was developed, including both a fetus and a maternal pelvis. Application of suprapubic pressure, rotation of the infant's shoulders, and delivery of the posterior arm following shoulder dystocia were each modeled, and delivery force and brachial plexus stretch were predicted. RESULTS: Compared with lithotomy alone, all maneuvers reduced both the required delivery force and brachial plexus stretch. The greatest effect was seen with delivery of the posterior arm, which showed a 71% decrease in anterior nerve stretch (3.9% vs 13.5%) and an 80% decrease in delivery force. CONCLUSION: The standard maneuvers met the objective of reducing the necessary delivery force compared with the lithotomy position alone. Brachial plexus stretch is also reduced when these maneuvers are used rather than continuing the delivery in lithotomy position.

The effect of yield damage on the viscoelastic properties of cortical bone tissue as measured by dynamic mechanical analysis.

We have previously shown, using Dynamic Mechanical Analysis (DMA), that the presence of a defect in cortical bone tissue affects the apparent viscoelastic properties of that bone. However, mechanically induced damage is more complex than a machined defect making it difficult to predict its effect on bone viscoelasticity. We performed DMA measurements before and after introduction of yield damage into cortical bone beams from sheep radii. The specimens were placed in a DMA machine and baseline measurements of storage modulus (E1) and loss factor (tandelta) were performed using a 3-point bending configuration for a frequency range of 1-10 Hz. Measurements were done in all four bending directions (cranial, caudal, medial, and lateral) in random order. After subjecting the specimens to monotonic yield damage in a servohydraulic testing machine with the load applied to the cranial surface, oscillatory tests were repeated. To supplement results from the current experiment, additional analyses were performed on data from experiments where bone was either cut or fatigue-loaded between viscoelasticity measurements. Introduction of mechanical damage increased tan delta and frequency sensitivity of E1, consistent with the assertion that increased energy dissipation in damaged bone might contribute to its increased resistance to fatigue and fracture.

Prolonged retention of the anorectic cobalt protoporphyrin in the hypothalamus and the resulting expression of Fos.

The anorectic cobalt protoporphyrin (CoPP) is known to elicit short-term hypophagia and long-term weight loss through unknown mechanisms in the brains of experimental animals. The goal of this work was to determine 1) if the prolonged duration of action of CoPP is related to its prolonged retention within the brain; and 2) with the use of immunohistochemical detection of Fos, the product of the early-immediate gene c-fos, which cells are activated after exposure to CoPP. These studies were carried out in male rats after intracerebroventricular administration of CoPP, 0.4 micromol/kg body wt, given under light halothane anesthesia. Residence of CoPP in the brain was determined by residual counts in dissected brains of (57)CoPP-injected rats. Fos immunoreactivity was mapped in coronal sections of rat brains 4-6 h after injection with CoPP. The results showed that (57)CoPP was retained in the hypothalamus preferentially compared with the cortex of the brain and could be detected in the hypothalamus for in excess of 5 wk. Fos activation was increased by CoPP, detected predominantly in neuronal rather than glial cells, and was markedly more robust in the hypothalamus than in other brain areas. Thus CoPP remains in the hypothalamus for prolonged periods and activates Fos expression in the hypothalamus.

The high frequency properties of brain tissue.

Computer modeling is becoming increasingly important in the realm of brain biomechanics and injury. New computer simulations range from modeling of brain surgery, a low frequency, high strain event, to predicting injury as a result of an impact to the head, a high frequency event with varying strain magnitudes. This range of modeling efforts requires characterization of the tissue over as wide a frequency and strain range as possible. Research done to date has concentrated on the low frequency properties of the tissue. Complex compression and complex shear moduli have been measured at frequencies up to 350 Hz. Impact modeling requires use of frequency data at significantly higher frequencies than these. The "wave-in-a-tube" ultrasonic method was applied to brain tissue to determine mechanical properties at frequencies between 100 kHz and 10 MHz. Of these properties, only complex bulk modulus |K*| is fairly invariant (2133 MPa) with respect to frequency. Complex shear and complex Young's moduli vary with frequency and approach an asymptotic upper limit. Some variation in complex Poisson's ratio was also observed.