Michele J. Grimm

Prediction of brachial plexus stretching during shoulder dystocia using a computer simulation model

OBJECTIVE The purpose was to study the impact of maternal endogenous and clinician-applied exogenous delivery forces on brachial plexus stretching during a shoulder dystocia event. STUDY DESIGN A computer software crash dummy model (MADYMO, version 5.4, TNO Automotive, Delft, The Netherlands) was modified on the basis of established maternal pelvis and fetal anatomic specifications. The brachial plexus was modeled as a spring, with mechanical properties that were based on previously reported experimental data. Increasing amounts of endogenous or exogenous loading forces were applied until delivery of the anterior fetal shoulder occurred. Brachial plexus deformation was assessed as percent stretch in the nerve (Change in length/Original length x 100). RESULTS With lithotomy positioning, both maternal endogenous and clinician-applied exogenous delivery forces were associated with brachial plexus stretching (15.7% vs 14.0%, respectively). McRoberts positioning reduced needed loading forces for delivery and resulted in 53% less brachial plexus stretch (6.6%). Downward lateral displacement of the fetal head was associated with a 30% increase in brachial plexus stretch (18.2%) compared with axial positioning of the head (14.0%). CONCLUSION Brachial plexus stretch varied as a result of the load required for delivery, the source of the applied force, pelvic orientation, and fetal head positioning. Maternally derived and clinician-applied delivery forces can both lead to brachial plexus deformation when shoulder dystocia is encountered. The McRoberts maneuver can reduce brachial plexus stretching. Management of fetal head position may also be important in reducing unnecessary brachial plexus stretch.

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 infants 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.

Mechanical Properties of the Cadaveric and Hybrid III Lumbar Spines

This study identified the mechanical properties of 10 cadaveric and 2 Hybrid III lumbar spines. Eight tests were performed on each specimen: tension, compression, anterior shear, posterior shear, left lateral shear, flexion, extension, and left lateral bending. Each test was run at a displacement rate of 100 mm/sec. The maximum displacements were selected to approximate the loading range of a 50 km/h Hybrid III dummy sled test and to be non-destructive to the specimens. Load, linear displacement, and angular displacement data were collected. Bending moment was calculated from force data. Each mode of loading demonstrated consistent characteristics. Load-displacement curves of the Hybrid III lumbar spine demonstrated an initial region of high stiffness followed by a region of constant stiffness. The exception was the tension tests, as the steel cables in the spine seemed to dominate the mechanical response in tensile loading. Loading curves of cadaveric spines demonstrated an initial region of low stiffness followed by a region of increasing stiffness, typically a feature of soft tissue response. Notable findings included the observation that the whole cadaveric lumbar spine specimens are stiffer in posterior than in anterior shear. This finding is in contrast to motion segment studies, in which the opposite trend is observed.

Neonatal brachial plexus palsy

The American College of Obstetricians and Gynecologists convened the Task Force on Neonatal Brachial Plexus Palsy to develop a comprehensive report summarizing a scientific literature on this subject. Clinically, neonatal brachial plexus palsy (NBPP) presents in a newborn as a weak or paralyzed upper extremity, with the passive range of motion greater than the active. The overall incidence of NBPP, both transient and persistent impairment, is 1.5 per 1,000 total births. Multiple reports in the peer-reviewed literature describe the occurrence of NBPP without concomitant clinically recognizable shoulder dystocia at the time of both vaginal and cesarean delivery. Chapter 1 of the report details the incidence of NBPP.

Work in progress - an Engineering Bridge Program - the foundation for success for academically at-risk students

As an urban institution, Wayne State University is charged with providing educational opportunities to students from varied backgrounds. Historically, many students entering the College of Engineering have not been calculus-ready. The 4-year retention rate of students who place into advanced algebra or below has been about 25%. In order to provide students who are interested in engineering with the best chance of academic success while maintaining the quality of the engineering degree programs, an Engineering Bridge Program was developed. Students are placed in the Bridge Program based on one or more of the following criteria: 1) science/math gpa from high school below 3.0; 2) Math ACT score below 22; or 3) placement into advanced algebra or below on the Universitys math placement exam. Students must complete a one-year program of math (through pre-calculus), chemistry, physics, English, and an Introduction to the Engineering Profession with a gpa of 3.0 or higher to progress into the pre-professional program. In addition to the coursework, designed to provide a strong foundation for engineering, students are placed in peer cohort groups that meet weekly with an engineering mentor - an upper division or graduate student in engineering. These peer groups provide Bridge students with a connection to their fellow students and a support group that introduces them to the University environment. The College advising staff also closely monitors Bridge students to provide early intervention if students have academic difficulties. Students who do not succeed in the Bridge Program receive advising to allow them to select a new major that fits their academic goals and talents. This prevents students from floundering in the College of Engineering for several years before being forced to change to another program. The program is evaluated based on both student retention rate and student academic success, as quantified by College gpa

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

BackgroundThe 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.MethodsA 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.ResultsNo 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.ConclusionTranscranial 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.

The Wave-in-a-Tube Method for Estimation of Mechanical Properties of Viscoelastic Materials Using Ultrasound

The wave-in-a-tube method allows for the estimation of material properties of gel-like, viscoelastic materials utilizing only a pair of matched ultrasonic pressure transducers. To employ this technique, a sample tube must be manufactured that (1) has an inside diameter that fits snugly around the element of the transducers being utilized, (2) is as long as the specimen size will allow given the diameter required, and (3) is made of a low-density, solid material. After construction of the container, the sample to be measured is placed in the tube with a pressure transducer fitted into each end with large air pockets eliminated. An ultrasonic pulse is sent through the sample, and the resulting waveform is analyzed per the Reynolds wave-in-a-bar method, yielding the magnitude of the complex moduli.