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Tobias A. Mattei, Brandon J. Bond, John W. Hafner Jr., Martin J. Morris, Jennifer Travis, Greg Hannah, Jim Webster and Julian J. Lin

Object

All-terrain vehicle (ATV) usage has grown tremendously over the years, reaching 9.5 million vehicles in use in 2007. Accompanying this growth has been a concomitant increase in rider morbidity (including traumatic brain and spine injuries) and death, especially in children. The purpose of this study was to define and measure, through field testing, those physical attributes intrinsic to riders, such as height, weight, and wingspan, which may have implications for ATV riders' safety.

Methods

Three field tests (J-hook, brake, and bump) were developed and performed to allow direct measurement of the lateral, longitudinal, and vertical dynamics in 5 riders of varying heights, weights, and wingspans. Two ATVs, a utility and a sport model, were tested for further comparisons. Data were acquired using a comprehensive data acquisition system attached to the ATVs. Assignment of individual rider/ATV test safety ratings and a rider/ATV Total Safety Rating were made from the results of these field tests.

Results

The J-hook test results demonstrated that larger rider wingspans positively influence ATV rider safety and mitigate against lateral instability. From the brake test it was determined that a 10-in (25.4-cm) longitudinal displacement, such as that experienced during a sharp deceleration, for a rider of any height or weight, breached the level of defined safety. As rider weight increased, displacement decreased. The bump test provided evidence that increased rider weight also mitigates against vertical displacement.

Conclusions

Individuals with light weights and small wingspans, such as those in the pediatric population, are under considerable risk of injury when operating an ATV due to lateral, longitudinal, and vertical operational instability.

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Tobias A. Mattei, Brandon J. Bond, Carlos R. Goulart, Chris A. Sloffer, Martin J. Morris and Julian J. Lin

Object

Bicycle accidents are a very important cause of clinically important traumatic brain injury (TBI) in children. One factor that has been shown to mitigate the severity of lesions associated with TBI in such scenarios is the proper use of a helmet. The object of this study was to test and evaluate the protection afforded by a children's bicycle helmet to human cadaver skulls with a child's anthropometry in both “impact” and “crushing” situations.

Methods

The authors tested human skulls with and without bicycle helmets in drop tests in a monorail-guided free-fall impact apparatus from heights of 6 to 48 in onto a flat steel anvil. Unhelmeted skulls were dropped at 6 in, with progressive height increases until failure (fracture). The maximum resultant acceleration rates experienced by helmeted and unhelmeted skulls on impact were recorded by an accelerometer attached to the skulls. In addition, compressive forces were applied to both helmeted and unhelmeted skulls in progressive amounts. The tolerance in each circumstance was recorded and compared between the two groups.

Results

Helmets conferred up to an 87% reduction in so-called mean maximum resultant acceleration over unhelmeted skulls. In compression testing, helmeted skulls were unable to be crushed in the compression fixture up to 470 pound-force (approximately 230 kgf), whereas both skull and helmet alone failed in testing.

Conclusions

Children's bicycle helmets provide measurable protection in terms of attenuating the acceleration experienced by a skull on the introduction of an impact force. Moreover, such helmets have the durability to mitigate the effects of a more rare but catastrophic direct compressive force. Therefore, the use of bicycle helmets is an important preventive tool to reduce the incidence of severe associated TBI in children as well as to minimize the morbidity of its neurological consequences.

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Tobias A. Mattei, Martin Morris, Kathleen Nowak, Daniel Smith, Jeremy Yee, Carlos R. Goulart, Anne Zborowski and Julian J. Lin

Object

Although several improvements have been observed in the past few years in shunt technology, currently available systems still present several associated problems. Among these, overdrainage along with its complications remains one of the great challenges for new shunt designs. To address the so-called siphoning effect, the authors provide a practical example of how it is possible to decouple the activation pressure and the pressure gradient across the valve through a 3–key component system. In this new shunt design, the flow is expected to depend only on the intracranial pressure and not on the pressure gradient across the valve, thus avoiding the so-called siphoning effect.

Methods

The authors used computer models to theoretically evaluate the mechanical variables involved in the operation of the newly designed valve, such as the fluid's Reynolds number, proximal pressure, distal pressure, pressure gradient, actual flow rate, and expected flow rate. After fabrication of the first superscaled model, the authors performed benchmark tests to analyze the performance of the new shunt prototype, and the obtained data were compared with the results predicted by the previous mathematical models.

Results

The final design of the new paddle wheel valve with the 3–key component antisiphoning system was tested in the hydrodynamics laboratory to prove that the siphoning effect did not occur. According to the calculations obtained using the LabVIEW program during the experiments, each time the distal pressure decreased without an increase in the proximal pressure (despite the range of the pressure gradient), the pin blocked the spinning of the paddle wheels, and the calculated fluid velocity through the system tended to zero. Such a situation was significantly different from the expected flow rate for such a pressure gradient in a siphoning situation without the new antisiphon system.

Conclusions

The design of this new prototype with a 3–key component antisiphoning system demonstrated that it is possible to decouple the activation pressure and the pressure gradient across the valve, avoiding the siphoning effect. Although further developments are necessary to provide a model compatible to clinical use, the authors believe that this new prototype illustrates the possibility of successfully addressing the siphoning effect by using a simple 3–key component system that is able to decouple the activation pressure and the pressure gradient across the valve by using a separate pressure chamber. It is expected that such proof of concept may significantly contribute to future shunt designs attempting to address the problem of overdrainage due to the siphoning effect.

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Tobias A. Mattei, Kalyani Nair, Martin Morris, Deric Cole, Michael Flatt, Carlos R. Goulart, Brian Kroeter, Shavonna Warren and Julian J. Lin

Object

Addressing overdrainage and its associated complications is still one of the greatest challenges for future shunt designs for normal-pressure hydrocephalus and idiopathic intracranial hypertension. Nevertheless, as evidenced by tap test procedures, a small amount of CSF drainage seems to be enough to relieve patients' symptoms in most cases and, therefore, in opposition to other types of hydrocephalus, continuous CSF drainage may not be absolutely warranted. In such a clinical scenario, intermittent controlled drainage of a small amount of CSF during specific periods of the day through a 2-system pump may provide several advantages over continuous drainage of current single-system shunts. The goal in this study was to design and test an innovative concept of a bicorporal pump composed of a 2-part system. The first component was designed to be implanted in the patient and act as a pump connected to standard catheter tubing. The second component was designed to be used as an external device outside of the body and function as a power supply and control system. Ultimately, flow will only occur when the system is powered by the external device.

Methods

Testing and comparisons were performed to evaluate free fluid flow and the maximal flow after pumping in the standing and supine positions. After this, the authors compared the hydrodynamic effects of 2 different housing systems (2- and 3-in systems). An attenuation test was performed to show the effects of electromagnetic forces at progressively increasing distances. Finally, a biocompatibility report of the raw material used in the pilot design was completed.

Results

In the supine position, the effect of pumping was observed to increase the volumetric flow at a rate similar to or higher than that yielded in the free-flow tests. In relation to the attenuation test, it was observed that the volume drops off fairly quickly as the air gap distance was increased until ultimately reaching zero, with approximately 15 mm between the 2 components. In relation to the testing force, the 2-in housing model showed a considerable increase in the required electromagnetic force over the 3-in housing.

Conclusions

The authors successfully designed and tested a new intermittent drainage system through a bicorporal shunt, which provides several advantages over current single-system continuous drainage pumps. According to the authors' benchmark results, the 3-in housing model seems to be a better choice as it requires less force from the external electromagnet control. Moreover, attenuation tests demonstrated that, for proper functioning, the gap distance between the external and implanted devices should not be greater than 15 mm. Such initial benchmark results confirm the feasibility of such innovative design and provide support for future testing of the system in in vivo animal models and in future clinical series.

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Tobias A. Mattei, Christopher Frank, Joshua Bailey, Edna Lesle, Alyssa Macuk, Matthew Lesniak, Ankit Patel, Martin J. Morris, Kalyani Nair and Julian J. Lin

Object

Simulation has become an important tool in neurosurgical education as part of the complex process of improving residents' technical expertise while preserving patient safety. Although different simulators have already been designed for a variety of neurosurgical procedures, spine simulators are still in their infancy and, at present, there is no available simulator for lumbar spine pathologies in pediatric neurosurgery. In this paper the authors describe the peculiarities and challenges involved in developing a synthetic simulator for pediatric lumbar spine pathologies, including tethered spinal cord syndrome and open neural tube defects.

Methods

The Department of Neurosurgery of the University of Illinois at Peoria, in a joint program with the Mechanical Engineering Department of Bradley University, designed and developed a general synthetic model for simulating pediatric neurosurgical interventions on the lumbar spine. The model was designed to be composed of several sequential layers, so that each layer might closely mimic the tensile properties of the natural tissues under simulation. Additionally, a system for pressure monitoring was developed to enable precise measurements of the degree of manipulation of the spinal cord.

Results

The designed prototype successfully simulated several scenarios commonly found in pediatric neurosurgery, such as tethered spinal cord, retethered spinal cord, and fatty terminal filum, as well as meningocele, myelomeningocele, and lipomyelomeningocele. Additionally, the formulated grading system was able to account for several variables involved in the qualitative evaluation of the technical performance during the training sessions and, in association with an expert qualitative analysis of the recorded sessions, proved to be a useful feedback tool for the trainees.

Conclusions

Designing and building a synthetic simulator for pediatric lumbar spine pathologies poses a wide variety of unique challenges. According to the authors' experience, a modular system composed of separable layers that can be independently replaced significantly enhances the applicability of such a model, enabling its individualization to distinctive but interrelated pathologies. Moreover, the design of a system for pressure monitoring (as well as a general score that may be able to account for the overall technical quality of the trainee's performance) may further enhance the educational applications of a simulator of this kind so that it can be further incorporated into the neurosurgical residency curriculum for training and evaluation purposes.