Evaluation of e-bike accidents in Switzerland.

BACKGROUND: The acceptance and usage of electric bicycles has rapidly increased in Switzerland in the last years. Hence this topic has been addressed by policy makers with the aim to facilitate new transport modes and, moreover, to improve their safety. METHODS: Police-recorded accidents of the years 2011 and 2012 involving a total of 504 e-bikers and 871 bicyclists were analysed. National figures were compared with those of a rural and an urban environment. RESULTS: Most e-bikers who were involved in accidents were 40-65 years old. It was found that most e-bikers sustained single accidents and that helmet usage was higher in the investigated rural environment than in the investigated urban area. The evaluation of the injury severity of e-bikers, particularly compared to bicyclists, lead to diverging results. CONCLUSIONS: The findings presented in this study are intended to serve as a benchmark since basic information on characteristics of e-bike accidents is provided. With respect to differences between the injury severity of e-bikers and bicyclists to-date no clear statement can be drawn. It is suggested to regularly evaluate e-bike accidents to show trends and/or identify changes.

Development of a model to mimic pleural space mechanics.

BACKGROUND: A simulator of the respiratory system which includes the pleural space is currently lacking. However, such mechanical models are essential to develop and test new medical devices regulating the pressure in the pleural space. OBJECTIVE: It was the aim of this study to develop a model which mimics the pleural space. The device should be able to represent biomechanical functions of the respiratory system and it is intended for applications in research and development to study pleural space mechanics. The system should allow adjusting parameters to simulate different kinds of breathing. Output parameters such as the pressure in pleural cavity or the breathing volume should be measured. METHODS: A mechanical lung simulator was developed. The chest wall is represented by an elastic shell in which silicone balloons were implemented to mimic the lung tissue. These two components establish a pleural cavity. Pressure sensors were installed to measure pressure in the pleural space and an aeroplethysmograph was positioned above the two lungs to measure flow. The system was assembled and tested under various conditions. RESULTS: Different tests demonstrated that the device is currently capable of simulating breathing volumes up to approx. 1700 ml. Different breathing characteristics including coughing can be simulated. Higher negative pressures especially during deep breathing were observed at the top of the lung because of higher balloon wall (lung) thickness in this area. It was possible to demonstrate the effect of certain changes of the lung tissue such as fibrosis with corresponding pressure recordings confirming known effects of such pathologies. CONCLUSIONS: The device allows simulating pressures in the pleural space during breathing at an advanced level and will be of use to develop and validate medical devices under laboratory conditions that control and regulate the pleural space. This represents a significant benefit to improve the development process for devices in this area.

Analysing the protective potential of padded soccer goalkeeper shorts.

OBJECTIVE: In this study, the potential of currently available padded soccer goalkeeper shorts to prevent hip injuries sustained in side jumps was investigated. DESIGN: Within the scope of this study, a survey among professional and amateur goalkeepers, trainers and the medical staff was performed. In addition, commercially available shorts were impact-tested using an artificial hip model. The results were compared with requirements established for hip protectors for elderly. RESULTS: The results of the survey found that contusions and abrasions were observed most often for all players. Fractures and arthritis were only reported by amateur players, whereas bursitis was more frequently observed by professional players. Amateurs have a significantly higher risk of injury than professional players, and the higher injury risk during training is significantly higher compared with the injury risk during a match. No difference of the injury risk was found between goalkeepers wearing padded shorts and those who did not. Impact tests indicated a wide range of performance of the currently available products. The padded shorts generally reduce impact forces, but mostly perform poorly. Only shorts that were made of visco-elastic foam fulfilled the basic requirements requested for hip protectors for elderly. CONCLUSIONS: The quality of most of the currently available goalkeeper shorts needs to be improved to effectively prevent hip injury sustained in side jumps.

[Hip injuries in professional and amateur soccer goalkeepers]. / Hüftverletzungen bei Fussballtorhütern unterschiedlicher Leistungsstufen.

Soccer goalkeeper often dive to the side loading their hip. Different hip injuries might result. Within the scope of this study the hip injury rate of professional and amateur soccer goalkeepers was investigated. Most often players suffer from contusions and abrasions. Bursitis is reported from professional players, but hardly from amateur players. Generally amateur players are injured more often than professional players. For all players the injury risk during exercise is significantly higher than during a match. The exercise frequency showed a weak link to incidence rate only. For age, gender and exercise intensity no influence of the injury rate was found. Artificial playground resulted in a higher injury rate than natural grass, although the difference was not statistically significant. It was noted that team coachs and players indicated a different perception of the injury rate. The use of protective sports wear (hip protectors) did not significantly influence the injury rate.

Kidney injury: an experimental investigation of blunt renal trauma.

BACKGROUND: The abdomen ranks third with regard to injured body regions, and urogenital trauma accounts for up to 10% of all abdominal injuries. Predictive numerical models are evolving as important tools for the development of preventative measures and preliminary clinical diagnostics. Such models require accurate biomechanical input data that at present is not sufficiently available. METHOD: The purpose of the present study was to determine the biomechanical response of whole, perfused porcine kidneys to blunt impact. Specifically of interest were the force-displacement characteristics of the organs, as well as the injury thresholds. Thirty nine young, adult pig kidneys (kidney mass 0.17 +/- 0.02 kg) were infused with physiologic saline solution, and impacted on their dorsal surface by a freely swinging right cylindrical pendulum. Two impact masses (2.1 and 4.7 kg) were used at varying impact velocities and corresponding impact energies. Resulting injuries were graded according to the AAST injury scale, and injury was related to impact mass, impact velocity, and impact energy. RESULTS AND CONCLUSIONS: It was determined that injury was best predicted by impact energy, and that for a given impact energy the resulting injury severity was relatively independent of either impact mass or impact velocity. For a moderate to severe injury, an impact energy threshold of 4 J, or a corresponding strain energy density of 25 kJ/m, was established. This information is essential to the development and implementation of accurate, predictive computational trauma models.

Anatomical hip model for the mechanical testing of hip protectors.

An anatomical hip model has been developed to simulate the impact load on the hip of a falling person wearing a hip protector. The hip consists of an artificial pelvis made of aluminium, linked by a ball-and-socket joint to an anatomically shaped steel femur (thigh bone). The femur is embedded in silicone material with a hip-shaped surface to allow realistic positioning of the protectors with accessory underwear. Additionally, the silicone simulates the damping and load-dispersal effect of soft tissue. A triaxial load sensor is integrated in the neck of the femur to measure the axial and cross-sectional force components in response to external impact forces on the hip. The performance of the hip model was investigated in drop tests and validated against biomechanical data. In a first series of measurements, the shock absorption of 10 different hip protectors, including both energy-absorbing and energy-shunting systems, was analysed. To determine the importance of hip protector placement, each protector was tested in the correct anatomical alignment over the hip and anteriorly displaced by 3 cm. Considerable differences were found between individual hip protectors in their effectiveness to reduce impact forces on the femur. Position of the hip protector also influenced the forces applied to the femur.

A finite element approach and experiments to assess the effectiveness of hip protectors.

The potential of hip protectors to prevent femur fracture is addressed in this study. A mechanical model of the human hip was developed and used to perform impact tests with different types of hip protectors. In addition a finite element model of the test device was established which allows simulations of the impact tests. The different principles of energy-shunting systems and energy-absorbing systems were demonstrated. Furthermore misplacement of a hip protector can be simulated. Hence the FE model was shown to be a suitable tool for future hip protector design.

Pressure aberrations inside the spinal canal during rear-end impact.

Minor soft tissue injuries of the cervical spine increasingly pose problems in public health. Such injuries are conveyed particularly often in rear-end automobile collisions at low impact speeds and it has been established that they may be associated with long-term impairment. As a possible cause for this type of injury it has been hypothesized that pressure pulses induced in cervical fluid compartments during the impact could damage the membrane of spinal nerve cells. To date, animal as well as cadaver experiments performed support this hypothesis. A theoretical analysis has been undertaken in order to investigate the pressure and flow pulse emerging in a cervical fluid compartment under conditions representing rear-end impacts with a Dv of 15 km/h. Using the finite element (FE) method, a three-dimensional model of the cervical spine was developed. The model consists of eight vertebrae (C1-T1), the intervertebral discs, the intervertebral joints, all the major ligaments, most of the neck muscles and the head. Additionally, a typical venous blood vessel was included. To determine the pressure behaviour inside the blood vessel, fluid-structure interaction was taken into account. For the time interval including the development of the S-shape, the pressure pulses were calculated and found to be in qualitative agreement with the reported measurements. The shear stresses acting on the vessel wall can be determined from the associated flow pulses. An extrapolation of the results into the interstitial space where nerve cells are located at this stage does not allow assessment of whether a damage threshold may be reached.

Whiplash injury: cases with a long period of sick leave need biomechanical assessment.

A total of 668 cases of cervical spine disorders (CSD) sustained in automotive collisions were analysed. All cases had a minimum sick leave duration of 4 weeks. To evaluate these cases a scheme was developed that takes into account technical, medical, and biomechanical aspects. For each case, the delta-v value of the underlying collision was estimated, the medical files were analysed, and a QTF (Québec Task Force) grade was assigned. In addition, the medical history of the patient was reviewed. It was found that the QTF grade for patients with pre-existing damage of the neck or pre-existing signs differed significantly from those patients without such a history. The overall assessment, which stated the extent to which the symptoms claimed could be explained by the impact, was also found to be significantly influenced by a history of neck injury. The results of the study showed that in about 50% of the cases where the technical analysis alone would not suggest that the symptoms shown could be explained by the impact, those symptoms could be explained when patient history and the collision circumstances were taken into consideration. It also found that medical evaluation based on a QTF grade alone cannot assess the explicability of claimed CSD without taking into account the collision circumstances. Therefore, the assessment of critical individual relevant biomechanical factors is necessary.

Comparison Tests of BioRID II and RID 2 with Regard to Repeatability, Reproducibility and Sensitivity for Assessment of Car Seat Protection Potential in Rear-End Impacts.

The objective of our study was to investigate the properties of the BioRID II and RID2 dummies regarding repeatability and reproducibility as well as their suitability to identify the protection potential of different car seats. For repeatability and reproducibility tests, three BioRID II and three RID 2 dummies at current build levels were seated on a rigid bench seat equipped with a head restraint, and mounted on a HyGe-type sled. The test velocity was prescribed by the proposed ISO-Pulse. For testing the interaction of the dummies with varying car seat geometries and mechanical properties and their ability to assess the protection potential of the seats, three seat types with passive and one seat with an active head restraint system from different car manufacturers were used. The seats were chosen due to their injury protection potential, indicated by accident field data and results of seat evaluation tests. One BioRID II equipped with a T1-load cell and one RID2 were positioned side-by-side on identical seats for each test. The tests were performed at velocities prescribed by the ISO-Pulse (deltav 16km/h / 8 g max.)and a more severe pulse (deltav 24km/h / 13 g max.). The dummy responses were interpreted by applying all currently proposed whiplash injury criteria (e.g. NIC, N(km), NDC, LNL). A comparison of these criteria shows their sensitivity for identification of the respective seat protection potential. This study examines the repeatability, reproducibility, kinematics and sensitivity of these two dummies in sled tests as well as their suitability with regard to the different injury criteria. The RID2 exhibited better repeatability and reproducibility than the BioRID II, because of its simpler mechanical design. The dummies did not give a consistent ranking of the low-speed, rear-end impact protection potentials of the four seat evaluated. More experience is needed to decide which dummy, injury criteria and limits should be used to assess the whiplash protection potential of seat designs.

Biomechanical assessment of soft tissue neck injuries in cases with long sick leave times.

A database was established by collecting 919 cases of claimed cervical spine disorders (CSDs) sustained in automotive accidents. All cases had a sick leave time of more than 4 weeks. Data was obtained from a major Swiss accident insurer. An assessment scheme was developed that took into account technical, medical, and biomechanical aspects. All cases were evaluated according to this scheme. The overall biomechanical assessment, that stated the extent to which the symptoms claimed could be explained by the impact, was found to be significantly influenced by the patient's history of CSD in terms of preexisting damage or preexisting symptoms. In 52% of the assessed cases, the CSD claimed could be explained with a combination of neck loading and also by considering the patient's medical history. Performing a solely technical analysis of the collision circumstances or a purely medical evaluation based on a Quebec Task Force (QTF) grade alone are insufficient to assess the accident-related explicability of claimed CSD. Biomechanically relevant individual factors have to be considered.

Mechanical modeling of soft biological tissues for application in virtual reality based laparoscopy simulators.

For application in a Virtual Reality (VR) based laparoscopic surgery simulator, computationally efficient algorithms for the description of the mechanical behavior of soft tissue have been developed. The explicit Finite Element Method has turned out to be a robust method for this purpose provided that absolute strain formulations are applied. Furthermore, a VR model of a uterus and its adnexe has been generated and simulation results are presented.