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Biomedical subjects

P Lövsund

Publications and source records attributed to P Lövsund.

At least 19 recordsLinked to original sources
PubMed2003

Head kinematics in mini-sled tests of foam padding: relevance of linear responses from free motion headform (FMH) testing to head angular responses.

The revised Federal Motor Vehicle Safety Standard (FMVSS) No. 201 specifies that the safety performance of vehicle upper interiors is determined from the resultant linear acceleration response of a free motion headform (FMH) impacting the interior at 6.7 m/s. This study addresses whether linear output data from the FMH test can be used to select an upper interior padding that decreases the likelihood of rotationally induced brain injuries. Using an experimental setup consisting of a Hybrid III head-neck structure mounted on a mini-sled platform, sagittal plane linear and angular head accelerations were measured in frontal head impacts into foam samples of various stiffness and density with a constant thickness (51 mm) at low (approximately 5.0 m/s), intermediate (approximately 7.0 m/s), and high (approximately 9.6 m/s) impact speeds. Provided that the foam samples did not bottom out, recorded peak values of angular acceleration and change in angular velocity increased approximately linearly with increasing peak resultant linear acceleration and value of the Head Injury Criterion (HIC36). The results indicate that the padding that produces the lowest possible peak angular acceleration and peak change in angular velocity without causing high peak forces is the one that produces the lowest possible HIC36 without bottoming out in the FMH test.

Acceleration↗
PubMed2002

Influence of the lateral ventricles and irregular skull base on brain kinematics due to sagittal plane head rotation.

Two-dimensional physical models of the human head were used to investigate how the lateral ventricles and irregular skull base influence kinematics in the medial brain during sagittal angular head dynamics. Silicone gel simulated the brain and was separatedfrom the surrounding skull vessel by paraffin that provided a slip interface between the gel and vessel. A humanlike skull base model (HSB) included a surrogate skull base mimicking the irregular geometry of the human. An HSBV model added an elliptical inclusion filled with liquid paraffin simulating the lateral ventricles to the HSB model. A simplified skull base model (SSBV) included ventricle substitute but approximated the anterior and middle cranial fossae by a flat and slightly angled surface. The models were exposed to 7600 rad/s2 peak angular acceleration with 6 ms pulse duration and 5 deg forced rotation. After 90 deg free rotation, the models were decelerated during 30 ms. Rigid body displacement, shear strain and principal strains were determined from high-speed video recorded trajectories of grid markers in the surrogate brains. Peak values of inferior brain surface displacement and strains were up to 10.9X (times) and 3.3X higher in SSBV than in HSBV. Peak strain was up to 2.7X higher in HSB than in HSBV. The results indicate that the irregular skull base protects nerves and vessels passing through the cranial floor by reducing brain displacement and that the intraventricular cerebrospinal fluid relieves strain in regions inferior and superior to the ventricles. The ventricles and irregular skull base are necessary in modeling head impact and understanding brain injury mechanisms.

Biomechanical Phenomena↗
PubMed2000

Neck injuries in car collisions--a review covering a possible injury mechanism and the development of a new rear-impact dummy.

A review of a few Swedish research projects on soft tissue neck injuries in car collisions is presented together with some new results. Efforts to determine neck injury mechanisms was based on a hypothesis stating that injuries to the nerve root region in the cervical spine are a result of transient pressure gradients in the spinal canal during rapid neck bending. In experimental neck trauma research on animals, pressure gradients were observed and indications of nerve cell membrane dysfunction were found in the cervical spinal ganglia. The experiments covered neck extension, flexion and lateral bending. A theoretical model in which fluid flow was predicted to cause the transient pressure gradients was developed and a neck injury criterion based on Navier-Stokes Equations was applied on the flow model. The theory behind the Neck Injury Criterion indicates that the neck injury occurs early on in the rearward motion of the head relative to the torso in a rear-end collision. Thus the relative horizontal acceleration and velocity between the head and the torso should be restricted during the early head-neck motion to avoid neck injury. A Bio-fidelic Rear Impact Dummy (BioRID) was developed in several steps and validated against volunteer test results. The new dummy was partly based on the Hybrid III dummy. It had a new articulated spine with curvature and range of motion resembling that of a human being. A new crash dummy and a neck injury criterion will be very important components in a future rear-impact crash test procedure.

Accidents, Traffic↗
PubMed2000

Comparison of car seats in low speed rear-end impacts using the BioRID dummy and the new neck injury criterion (NIC).

Long-term whiplash associated disorders (WAD) 1-3 sustained in low velocity rear-end impacts is the most common disability injury in Sweden. Therefore, to determine neck injury mechanisms and develop methods to measure neck-injury related parameters are of importance for current crash-safety research. A new neck injury criterion (NIC) has previously been proposed and evaluated by means of dummy, human and mathematical rear-impact simulations. So far, the criterion appears to be sensitive to the major car and collision related risk factors for injuries with long-term consequences. To further evaluate the applicability of NIC, four seats were tested according to a recently proposed sled-test procedure. 'Good' as well as 'bad' seats were chosen on the basis of a recently presented disability risk ranking list. The dummy used in the current tests was the Biofidelic Rear Impact Dummy (BioRID). The results of this study showed that NICmax values were generally related to the real-world risk of long-term WAD 1-3. Furthermore, these results suggested that NICmax calculated from sled tests using the BioRID dummy can be used for evaluating the neck injury risk of different car seats.

Acceleration↗
PubMed2000

Strain relief from the cerebral ventricles during head impact: experimental studies on natural protection of the brain.

Physical models of the parasagittal human skull/brain have been tested to investigate whether the cerebral ventricles provide natural protection of the brain by relieving strain during head rotation. A sophisticated model included anatomical structures, and a semicircular model consisted of a cylinder divided into two semicircles. Silicone gel simulated the brain and was detached from the vessel by a layer of liquid paraffin simulating the cerebrospinal fluid. Both models were run with and without an elliptical inclusion filled with liquid paraffin simulating a cerebral ventricle. The 2D models were exposed to angular acceleration by a pendulum impact causing 7600 rad/s2 peak rotational acceleration with 6 ms pulse duration. After rotating 100 degrees, the models were decelerated during 30 ms. The trajectory of grid markers was analyzed from high-speed video (1000 frames/s). Rigid-body displacement, shear strain and principal strain were determined from the displacement of three-point sets inferior and superior to the ventricle. For the subventricular (inferior) region in the sophisticated model, approximately 40% lower peak strain values were obtained in the model with ventricle than in the one without. Subcortical displacement was reduced by 12%. Corresponding strain reduction in the subcortical (superior) region was approximately 40% following the acceleration and 25% following the deceleration. Similar but less pronounced effects were found for the semicircular model. The lateral ventricles play an important role as strain relievers and provide natural protection against brain injury.

Brain↗
PubMed1998

Injury probability and risk in frontal crashes: effects of sorting techniques on priorities for offset testing.

Front occupant exposure, MAIS2+ and MAIS3+ injury risk, and maximum-injured body regions were studied in frontal offset impacts. The effect of overlap amount was evaluated in three data subsets from 9,902 accident-involved Volvo cars with at least SEK35,000 (= US$5,000) damage. The subsets were selected by a MAIS2+ or MAIS3+ injured co-occupant or by an equivalent barrier speed (EBS) > 20 mph, and consisted of 661 or 249 cases and 654 cases, respectively. Age and gender effects were minimized. Collisions with 1/3 to 2/3 overlap were most frequent, but the most injurious crash type was influenced by the data sorting technique. The EBS criterion seemed to select crashes of more comparable severity and this dataset may be most appropriate to evaluate overlap effects. With EBS > 20 mph, the highest injury risk occurred in 1/3 overlap crashes, at 62% for MAIS2+ and 44% for MAIS3+ injury. This was two to three times higher than the corresponding risk in full frontal crashes. Head and chest were the most severely injured body regions, but lower-extremity injuries became more important as overlap decreased.

Accidents, Traffic↗
PubMed1998

Car occupant safety in frontal crashes: a parameter study of vehicle mass, impact speed, and inherent vehicle protection.

A new mathematical model was developed to estimate average injury and fatality rates in frontal car-to-car crashes for changes in vehicle fleet mass, impact speed distribution, and inherent vehicle protection. The estimates were calculated from injury fatality risk data, delta-V distribution and collision probability of two vehicles, where delta V-depends on impact speed and mass of the colliding vehicles. The impact speed distribution was assumed to be unaffected by a change in fleet mass distribution. The results showed that safety in frontal crashes would improve 27-35% by a 10% increase in fatality risk parameters, which reflected substantial improvement in inherent vehicle protection. A 40% safety improvement was attained by a 10% impact speed reduction. Consequences of vehicle fleet mass were not as strong, but depended on the average mass ratio of the fleet. A reduction in mass range would be the most beneficial, while a uniform mass reduction of 20% would increase the fatality rate by 5.4%. The model estimates trends in traffic safety and may help to identify priorities in active and passive safety.

Acceleration↗
PubMed1998

[Nerve cell damages in whiplash injuries. Animal experimental studies].

Mechanical loading of the cervical spine during car accidents often lead to a number of neck injury symptoms with the common term Whiplash Associated Disorders (WAD). Several of these symptoms could possibly be explained by injuries to the cervical spinal nerve root region. It was hypothesised that the changes in the inner volume of the cervical spinal canal during neck extension-flexion motion would cause transient pressure changes in the CNS as a result of hydro-dynamic effects, and thereby mechanically load the nerve roots and cause tissue damage. To test the hypothesis, anaesthetised pigs were exposed to experimental neck trauma in the extension, flexion and lateral flexion modes. The severity of the trauma was kept below the level where cervical fractures occur. Transient pressure pulses in the cervical spinal canal were duly recorded. Signs of cell membrane dysfunction were found in the nerve cell bodies of the cervical spinal ganglia. Ganglion injuries may explain some of the symptoms associated with soft-tissue neck injuries in car accidents. When the pig's head was pulled rearward relative to its torso to resemble a rear-end collision situation, it was found that ganglion injuries occurred very early on in the neck motion, at the stage where the motion changes from retraction to extension motion. Ganglion injuries did not occur when pigs were exposed to similar static loading of the neck. This indicates that these injuries are a result of dynamic phenomena and thereby further supports the pressure hypothesis. A Neck Injury Criterion (NIC) based on a theoretical model of the pressure effects was developed. It indicated that it was the differential horizontal acceleration and velocity between the head and the upper torso at the point of maximum neck retraction that determined the risk of ganglion injuries.

Animals↗
PubMed1996

Foot-ankle injuries: influence of crash location, seating position and age.

Foot-ankle injuries have increased in relative importance in recent years. As a basis for future countermeasures, an epidemiology study has been undertaken using Swedish accident data from Folksam Insurance. The database consists of 805 foot-ankle injuries out of 57,949 car occupant injuries reported from 1985 to 1991. The influence of crash location, seating position and occupant age is determined for the frequency, incidence and rate of foot-ankle injury in car crashes. Frontal car crashes produce 76% of the AIS 2-3 foot-ankle injuries with 13% in side impacts and 8% in roll-overs. The rate of AIS 2-3 foot-ankle injury is 24.7 per 1000 occupants injured in all crash locations and is similar irrespective of seating positions. Ankle fractures and sprains both occur at an incidence of 3.7 per 1000 injuries, followed by malleolus fractures at 2.7 and midtarsal fractures at 2.4. The foot-ankle injury incidence and rate are significantly greater (p < 0.01) in near oblique-frontal crashes than for 12 o'clock frontals. For drivers in 11 o'clock and front passengers in 12 o'clock, the incidence is 27.8 per 1000 injuries as compared to 17.5 for drivers and front passengers in 12 o'clock crashes. Occupant age is not as significant as seating position and crash location; however, there are higher incidences for rear occupants > or = 60 years old in oblique frontal crashes. Using the new AAAM Impairment Injury Scale (IIS), 48% of the foot-ankle injuries are rated with residual impairment IIS 1-2. The incidence in near-seated occupants is 1.5 times greater in oblique frontal crashes than in frontals. The incidence for IIS 1-2 impairment in near oblique-frontal crashes is 12.8 per 1000 occupant injuries as compared to 8.3 in frontal crashes.

Abbreviated Injury Scale↗
PubMed1996

The influence of seat-back and head-restraint properties on the head-neck motion during rear-impact.

The influence of different seat properties on the head-neck motion during a low-velocity rear-end impact was tested using a Hybrid III-dummy fitted with a modified neck (RID-neck). The results show that by modifying the properties of the seat-back and head-restraint it is possible to influence the head-neck kinematics to a great extent. It was possible to virtually eliminate the neck extension motion during a rear-impact. This will hopefully result in a significant decrease in neck injury risk in real world rear-impacts.

Acceleration↗
PubMed1996

Membrane leakage in spinal ganglion nerve cells induced by experimental whiplash extension motion: a study in pigs.

Nerve cells in the cervical and upper thoracic spinal ganglia were examined for possible plasma membrane leakage, as revealed by their ability to exclude a dye-protein complex, after experimentally induced whiplash in a pig model system. The rationale for this approach is found in the fact that the interstitium of spinal ganglia differs from most other parts of the nervous system in that it lacks a barrier, allowing blood constituents to gain access. The dye Evans blue, which rapidly conjugates with blood proteins, is found in the interstitium of normal spinal ganglia after intravenous injection, but it is excluded from the nerve cells and their enveloping satellite cells. In contrast, after a simulated whiplash extension trauma many of the nerve cells were stained, reflecting the inability of their plasma membranes to exclude the dye-protein complex. Morphometric measurements revealed that the highest frequency of cellular dye uptake was observed in the C4-C7 spinal ganglia (mean 16 - 18%; range 5-27%). The blood-nerve barrier of the adjacent nerve fascicles remained intact, with rare exception. Several factors are considered to contribute to the induction of these cell abnormalities in the spinal ganglia after an experimentally induced, simulated whiplash trauma in this pig model system.

Animals↗
PubMed1993

Life-threatening and disabling injuries in car-to-car side impacts--implications for development of protective systems.

Improvements to the passive safety of cars in lateral collisions are of great importance. This study of injuries in car side collisions in Sweden by the use of two evaluation methods has been performed to establish the basis for future development of protective systems for this type of accident. The Folksam car accident data file has been used. Injuries were found to be twice as common for near-side than for far-side* occupants in car to car impacts. Serious to fatal (AIS 3-6) injuries to belted front seat occupants in near side impacts (10% of all injuries) were compared with the estimated number of injuries to different parts of the body with risk of serious consequences (RSC)--either deaths or permanent disabilities (4.5% of all injuries). The two injury evaluation methods resulted in different ranking orders. AIS 3-6 injuries were received by the chest (37%), abdomen/pelvis (25%), and the head (15%). The RSC method gave a ranking order of head (25%), neck (21%), leg (15%), chest (14%), and abdomen/pelvis (11%). The method of evaluating AIS 3-6 injuries emphasizes only the threat to life. The RSC method also takes into account the risk of disabilities. Injuries to the neck and the leg were found to be most disabling, whilst the injuries to the head, chest, and abdomen/pelvis were the most life threatening. The study also shows that elderly people receive significantly more chest injuries (relative to the number of head injuries), on average four times more than young people.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents, Traffic↗
PubMed1993

A method for studying the biomechanical load response of the (in vitro) lumbar spine under dynamic flexion-shear loads.

A method was developed to study the biomechanical response of the lumbar motion segment (Functional Spinal Unit, FSU) under a dynamic (transient) load in flexion. In order to inflict flexion-distraction types of injuries (lap seat-belt injuries) different load pulses were transferred to the specimen by means of a padded pendulum. The load response of the specimen was measured with a force and moment transducer. The flexion angulation and displacements were determined by means of high-speed photography. Two series of tests were made with ten specimens in each and with two different load pulses: one moderate load pulse (peak acceleration 5 g, rise time 30 ms, duration 150 ms) and one severe load pulse (peak acceleration 12 g, rise time 15 ms, duration 250 ms). The results showed that the moderate load pulse caused residual permanent deformations at a mean bending moment of 140 Nm and a mean shear force of 430 N at a mean flexion angulation of 14 degrees. The severe load pulse caused evident signs of failure of the segments at a mean bending moment of 185 Nm and a mean shear force of 600 N at a mean flexion angulation of 19 degrees. Significant correlations were found between the load response and the size of the specimen, as well as between the load response and the bone mineral content (BMC) in the two adjacent vertebrae. Comparisons with lumbar spine response to static flexion-shear loading indicated that the specimens could withstand higher bending moments before injury occurred during dynamic loading, but the deformations at injury tended to be smaller for dynamic loading.

Acceleration↗
PubMed1993

The ultimate flexural strength of the lumbar spine and vertebral bone mineral content.

Flexion-distraction injuries (lap seat-belt injuries resulting from car accidents) were simulated by exposing 16 lumbar functional spinal units (FSUs) to a combined quasistatic load of bending and shearing in the sagittal plane. The load response of the FSU was measured by means of a force and moment transducer. Displacements and angulations were measured and calculated by means of dial gauges and photographs taken after each loading step. The mean angulation between the vertebrae just before total rupture was 20 degrees. The ultimate values of bending moment, shear force, and bending stiffness were correlated with the bone mineral content (BMC), and so were the horizontal and vertical displacements determined around the yield point on the load-displacement curve.

Accidents, Traffic↗
PubMed1992

The mechanism of initial flexion-distraction injury in the lumbar spine.

The threshold for flexion-distraction injuries was determined on lumbar functional spinal units exposed to a combined flexion-shear load in the sagittal plane. The specimens could resist a bending moment of 121 Nm and a shear force of 486 N at the first sign of a permanent deformation of the osteoligamentous components, which occurred at 78% of the assumed ultimate strength of each specimen. The flexion angulation was 16 degrees. The bone mineral content determined in adjacent vertebrae by means of dual photon absorptiometry was an accurate predictor of structural properties of the entire functional spinal unit even at the first sign of a substantial structural injury and not only at ultimate failure as previously demonstrated.

Bone Density↗
PubMed1991

Effects on driving performance of visual field defects: a driving simulator study.

To elucidate the possible traffic safety risks induced by visual field defects, a method was developed based on a driving simulator. The capacity to detect stimuli of different sizes appearing in 24 different positions on the screen in front of the driver was measured. Two groups of normal subjects and a number of subjects with different visual field defects were studied. In the groups of normals, the median reaction times were fairly homogenous. There was a slight difference between central and peripheral stimuli, which was somewhat larger for the older subjects. Among the subjects with field defects, the individual variations were very dominant. Very few of these showed a capacity to compensate for their deficiency. In order to gain insight into possible compensatory mechanisms of these persons, eye movement recordings were made. The results indicate that the visual search pattern may be of importance in this respect. Some comparisons with respect to detection capacity were also made with one-eyed subjects and with optically generated field restrictions (spectacles and spectacle frames).

Adult↗
PubMed1990

Ultimate strength of the lumbar spine in flexion--an in vitro study.

The ultimate strength in flexion of 16 lumbar functional spinal units (FSU) was determined. The specimens were exposed to a combined static load of bending and shearing in the sagittal plane until overt rupture occurred (simulated flexion-distraction injuries). The biomechanical response of the FSU was measured with a force and moment platform. Mechanical displacement gauges were used to measure vertical displacements (flexion angulation) of the specimens. Photographs were taken after each loading step for determination of horizontal displacements and the centre of rotation. The lumbar FSU could resist a combination of bending moment and shear force of 156 Nm and 620 N respectively, before complete disruption occurred. The tension force acting on the posterior structures was 2.8 kN. The flexion angulation just before failure was 20 degrees and the anterior horizontal displacement between the upper and lower vertebrae was 9 mm. The centre of rotation was located in the posterior part of the lower vertebral body. The bone mineral content in the vertebrae appeared to be a good predictor of ultimate strength of the lumbar FSU. Knowledge of the biomechanical response of the lumbar spine under different static traumatic loads is a first step to better understand the injury mechanisms of the spine in traffic accidents.

Biomechanical Phenomena↗