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Biomedical subjects

N M Alem

Publications and source records attributed to N M Alem.

4 recordsLinked to original sources
PubMed1997

Effects of weight and center of gravity location of head-supported devices on neck loading.

A comprehensive study of the effect of Head-Supported Devices (HSDs) on neck loading during helicopter accidents is presented. The new Articulated Total Body (ATB) model which treats the neck as a deformable segment was used for crash simulation. Different categories of human and manikin subjects were considered under several crash scenarios. Simulations were theoretically designed to include a wide range of HSDs by changing their weights and center of gravity (CG) locations relative to the head, and studying the effects of these changes. Since HSDs were only theoretically included in the model, detachment of specific detachable devices used in most military applications was not modeled in the study. Hence, two typical detachable devices were modeled and selected simulations were repeated and compared not only to provide a measure of accuracy for the original results but also to see the effect of separation of these devices from the helmet.

Accidents, Aviation↗
PubMed1996

Injury risk for research subjects with spina bifida occulta in a repeated impact study: a case review.

Spina bifida occulta (SBO) occurs in 18-34% of the normal U.S. population. Recently, 16.5% of normal, asymptomatic male soldier volunteer candidates in a U.S. Army Aeromedical Research Laboratory ride motion study were excluded from the study because they had SBO at one vertebral level. Disqualifying this percentage of screened research subject candidates threatened the timely completion of the schedule-intense protocol. Although one study suggests that SBO at spinal level S1 has a higher incidence of posterior disc herniation, the preponderance of clinical literature reports that spina bifida occulta is not a medical problem. The impact literature indicates that lumbosacral vertebral bodies fracture at 7.14 kN in static compression and 20+ G during dynamic vertical impacts. In this paper, we examined the human data observed in ejection seat incidents, the rationale for excluding volunteers with single level SBO and the path of axial load transmission through the lumboscral spine. Based on the findings, we concluded that research volunteers with single level SBO are not at increased risk for injury and recommended inclusion of these volunteers in future studies involving repeated axial impacts due to ride motion.

Adolescent↗
PubMed1996

A correlative investigation of simulated occupant motion and accident report in a helicopter crash.

BACKGROUND: In the late 1980's, an Army Apache helicopter crashed during a training mission, resulting in fatal injuries to the rear seat pilot and survivable injuries to the front seat copilot. U.S. Army investigators assessed the aircraft damage and aircrew injuries, and examined the helmets, restraint systems, and crashworthy seats. HYPOTHESIS: Computer simulations that approximate an actual crash event can provide insightful output (human body motions and forces on the human body) that illuminates our understanding of the injury dynamics and the effect of safety systems designed to minimize injury. METHODS: Crash kinematics and vehicle accelerations were derived from the investigation and inferred from the aircraft damage, and input to a computer-based analytical simulation that calculated the dynamics and forces to which the crew were exposed. RESULTS: We treat the simulation like a looking glass into the event, revealing how and when safety devices could have responded during the crash, and the nature of injury-producing forces experienced by the occupants. Computer simulated whole-body and head-neck motion are graphically displayed, along with plots of joint forces, seat stroke, harness belt acceleration, and occupant accelerations. CONCLUSIONS: The calculated motions and forces indicated that injuries found in the accident were likely, hence the simulation may indeed be representative of the actual event.

Acceleration↗