Experimental studies of lateral stress to transverse fractured femora treated with external fixation.

As part of a postmortem research project 9 beagle femora were dynamically tested by means of three-point bending. The test device was a spring driven impactor with an impact velocity of 3 m/s. Maximum bending force, deflection and force-deflection history were documented. After the impact transverse fractures were observed in 6 specimens, while another 3 specimens showed short oblique fractures. The fractured femora were treated realistically with external fixation (triax monotube) and again loaded on the impactor. After this treatment of the specimens and dynamic loading comminuted fractures occurred. In 7 cases all 4 pins were distorted. While there was only a small difference between the mean bending force of 751.01 N before and 729.54 N after treatment, a significant difference in terms of deflection and bending stiffness showed with p = 0.0039 for both parameters. This experimental result means that in cases of transverse fractures caused by ventral force only 9.6 % of the initial bending stiffness is obtained after stabilization with external fixation. Considering the fact that the use of external fixation protracts the time to bone consolidation of transverse fractures, this method cannot be designed as the therapy of choice.

Traumatology of the traffic accident--dead people for the safety in traffic.

Since 1970, traumatomechanics has been a focal point in research at the Institute for Legal Medicine and Traffic Medicine in Heidelberg. Here, the main topics are the understanding of the interrelation between mechanical strain and the resulting degree of injury; at the forefront of all interest is the determination of the mechanical resilience in humans, their organs and tissues. Important are not only the means, but likewise the individual strain tolerance and the causes for its variability. Their understanding leads to scientifically justifiable expert's reports. In safety research, these data are of major importance for the validation of crash-dummies and for the improvement of safety protection systems. Before this background, national and international institutions have supported numerous projects. With the help of 2 examples, the Thorax-Trauma-Index (TTI) and the synergy between safety belt and airbag, the relevance of these data for international regulatory provisions and the progress in safety practice are illustrated. Some traumatomechanical insights can only be gathered from human corpses. Legal prerequisites and ethical problems of experiments with corpses are discussed.

Prediction of cervical spine injury risk for the 6-year-old child in frontal crashes.

This article presents a series of 49 km/h sled tests using the Hybrid III 6-year-old dummy in a high-back booster, a low-back booster, and a three-point belt. Although a 10-year review at a level I trauma center showed that noncontact cervical spine injuries are rare in correctly restrained booster-age children, dummy neck loads exceeded published injury thresholds in all tests. The dummy underwent extreme neck flexion during the test, causing full-face contact with the dummy's chest. These dummy kinematics were compared to the kinematics of a 12-year-old cadaver tested in a similar impact environment. The cadaver test showed neck flexion, but also significant thoracic spinal flexion which was nonexistent in the dummy. This comparison was expanded using MADYMO simulations in which the thoracic spinal stiffness of the dummy model was decreased to give a more biofidelic kinematic response. We conclude that the stiff thoracic spine of the dummy results in high neck forces and moments that are not representative of the true injury potential.

Evaluation of the Performance of the THOR-alpha Dummy.

Six European laboratories have evaluated the biomechanical response of the new advanced frontal impact dummy THOR-alpha with respect to the European impact response requirements. The results indicated that for many of the body regions (e.g. shoulder, spine, thorax, femur/knee) the THOR-alpha response was close to the human response. In addition, the durability, repeatability and sensitivity for some dummy regions have been evaluated. Based on the tests performed, it was found that the THOR-alpha is not durable enough. The lack in robustness of the THOR-alpha caused a problem in completing the full test program and in evaluating the repeatability of the dummy. The results have demonstrated that the assessment of frontal impact protection can be greatly improved with a more advanced frontal impact dummy. Regarding biofidelity and injury assessment capabilities, the THOR-alpha is a good candidate however it needs to be brought up to standard in other areas. Based on the results obtained recommendations were defined for the improvement of the THOR-alpha dummy.

Blunt renal trauma: biomechanics and origination of renal lesions.

OBJECTIVES: Computer-assisted simulation of trauma is supposed to improve protective systems in traffic and risky leisure activities. In case of blunt renal injury biomechanical data being concerned with kidneys as a whole are extremely sparse. To enable three-dimensional simulations this study should supply important data of the renal biomechanics and elucidate the relationship between force distribution and origination of renal lesions. MATERIALS & METHODS: The present study investigated 66 isolated uninjured porcine kidneys using a drop impactor. Changes in deformation, brake force of power, deceleration and intrapelvic pressure are depicted while varying energy application between 1.4 and 14.2J. Lesions were detected by cross-dissecting the organs into slices. RESULTS: The measured values reflect a high correlation between load energy or brake force of power and deformation. Except the intrapelvic pressure all biomechanical parameters rise under increasing energy load. Comparing the different parameters over time a simultaneous concurrence of maximum brake force of power, deceleration and intrarenal pressure can be shown, the peak of deformation was reached belatedly. CONCLUSIONS: The paths of biomechanical curves prove a viscoelastic behaviour of the kidney. In contrast to the literature the region principally bearing the load seems to be the collision zone between renal pelvis and cortex where first lesions appear. This is mainly caused by the fluid filled pelvis, an incompressible support, that is supposed to change its shape after exceeding energy application of about 4J.

Prediction of cervical spine injury risk for the 6-year-old child in frontal crashes.

This paper presents a series of 49 km/h sled tests using the Hybrid III 6-year-old dummy in a high-back booster, a low-back booster, and a three-point belt. Although it is shown that non-contact cervical spine injuries are rare in correctly restrained children in this age group, neck loads exceeded published injury thresholds in all tests. The dummy kinematics were compared to the kinematics of a 12-year-old cadaver tested in a similar impact environment. This comparison was expanded using MADYMO simulations. It is concluded that the stiff thoracic spine of the dummy results in high neck forces and moments that are not representative of the true injury potential.

Teaching model for intraoperative spinal sonography in spinal fractures. An experimental study.

To improve the technique of intraoperative sonography of the spinal canal, a teaching model of the thoracolumbar spine was developed. It allows to simulate the typical spinal stenosis of a vertebral fracture and the sonographic procedure to detect and measure such a lesion. Moreover, partial laminectomy and modification of a fixateur interne set-up, which are preconditions for successful sonography, can be simulated. Independent of the surgical qualification, a high precision in sonographic localisation and measurement of the spinal canal stenosis was achieved by the training. The results could be validated in the cadaveric model. Thus, sonographic expertise acquired with the teaching model proved to be reliable in the clinical situation.

[Biomechanics of combined Kirschner wire osteosynthesis in the human model of unstable dorsal, distal radius fractures (Colles type)]. / Biomechanik der kombinierten Kirschnerdraht-Osteosynthese am humanen Modell der dorsal instabilen, distalen Radiusfraktur (Colles-Typ).

In an experimental study, the biomechanical qualities of the combined Kirschner wire osteosynthesis (KWO) in the unstable Colles' fracture were analyzed. This type of pin fixation is our preferred osteosynthesis in the treatment of unstable Colles' fracture because it allows immediate functional therapy. It represents a modification of Kapandji's dynamic KWO, compensating for the insufficient volar stability by means of the conventional static KWO. Clinical experience according to the anatomical and functional results, was very encouraging suggesting that a clinical concept based on the biomechanical principles of combined KWO and its single components should be constituted. Simulation of the unstable Colles' fracture was realized by dorsal wedge osteotomy of the distal end of the radius using cadaveric material. This fracture model was subsequently pinned using the different KWO types and tested by a standardized vector energy testing device regarding its stability in the four main loading directions. The combined KWO unifies the advantage of volar stability of the conventional KWO with the high dorsal stability of dynamic KWO. The main functional principle of dynamic KWO with regard to its axial stability consists in the repositioning of the dorsal bone fragmentation zone and hence the reconstitution of cortical load transmission. Besides its good stabilization, dynamic KWO also leads to optimal alignment of the distal metaphyseal fragment. Furthermore, the experiments yielded important information about technical aspects of the surgical procedure, which helps us to avoid anatomical and functional deficiencies. Based on these experimental findings, the surgical technique of combined KWO was standardized.

[The prospects for Kirschner-wire osteosynthesis in the dorsally unstable distal radius fracture (Colles' type)]. / Perspektive der Kirschnerdraht-Osteosynthese bei der dorsal instabilen, distalen Radiusfraktur (Colles-Typ).

The following experimental study was conducted to develop biocompatible methods of osteosynthesis in fractures of the distal radius and to evaluate their stability. A model of dorsal wedge osteotomy in the distal radial metaphysis was used to develop the surgical technique and to test the stability of the alternative methods of osteosynthesis. The concept for this model was based on commercially available materials which were either biodegradable or osteoconductive. Four different forms of biocompatible osteosynthesis were compared to combined Kirschner wire osteosynthesis (KWO), our preferred method of treatment of unstable Colles fracture. Biocompatible osteosynthesis was achieved with an invasivity and stability comparable to that of KWO. In conclusion, injection osteosynthesis exceeded the other biocompatible methods of osteosynthesis in all respects. Regarding the recent developments in injectable materials for osteosynthesis it offers the best perspective for clinical application.

[Quantitative trauma mechanics in pelvic fracture]. / Zur quantitativen Traumatomechanik der Beckenfraktur.

Quasistatic loading of the isolated pelvis and of the pelvis in situ is reported; dynamic loading with an impactor and on 90 degrees car/car side impact are then considered. The isolated pelvis was loaded laterally at the ala of the ilium and the pelvis in situ in the anterior-posterior direction in the area of the symphysis with universal dynamometer; the loading profile was a rigid disk 150 mm in diameter. Some dynamic tests were performed with an impactor with rigid disk 80 mm in diameter as impact surface; the impact was applied against the trochanter major area at a velocity of 30-35 km/h. Otherwise, the pelvic area was stressed by impact through the intrusion of the car side or by impaction of the pelvis against a rigid wall. In the tests conducted with isolated pelves, forces of 850-4850 N were measured; pelvic fractures were observed, specifically fractures of the acetabular margin, pubic bone, and ischium, and comminuted fractures of the symphysis and the iliosacral. In the impactor tests, forces of 6.5-11 kN were enough to cause, pelvic fracture except in one case, and fractures of the femoral neck were found in some cases in addition. With quasistatic anterior-posterior loading of the pelvis in situ, forces of 4,700-10,000 N were measured in cases in which fractures were found.

The influence of age on injury severity of restrained front seat occupants in head-on collisions.

This excerpt is part of a large-scale retrospective study on the interrelationship between accident severity and injury severity. A multivariate analysis of 319 cases of restrained front seat occupants involved in car-to-car head-on collisions showed the significant influence of the energy equivalent speed (EES) and age of the occupants on the number of rib fractures and sternum fractures. Three hundred occupants sustained no rib fractures, nine occupants one to 16 rib fractures, and ten occupants 17 to 32 rib fractures. In these three groups the EES increased from 35 km/h (no rib fractures) to 55 km/h (one to 16 rib fractures) and to then to 67 km/h (17 to 32 rib fractures). The average age in these groups was 34, 55 and 57 years respectively. Twenty-four occupants sustained sternum fractures. The average values of the EES and the average age were: in the group with sternum fractures: 56 km/h; 50 years old; in the group without sternum fractures: 35 km/h; 34 years old. The probability of sustaining fatal injuries in a head-on collision depended on the EES as well as the age of the occupant. At an EES of 60 km/h the probability of fatal injuries was 0.05% in the group < 30 years and 35% in the group > 59 years. Fifty-eight per cent of the occupants with sternal fractures had rib fractures as well; 46% of the occupants with rib fractures also had sternal fractures. The results were compared to the results of 185 post-mortem simulations of head-on collisions from the year 1973 to 1978. In post-mortem simulations the number of rib fractures and sternum fractures was influenced by vehicle decelerations and the age of the test subjects. The number of rib fractures increased at higher collision speeds, higher decelerations and increased age; the number of sternum fractures increased at higher deceleration and increased age of the test subjects. Seventy-two per cent of the test subjects with sternal fractures had rib fractures; 91% of the subjects with rib fractures had sternal fractures.

Bioresorbable pins and screws in paediatric traumatology.

Bioresorbable implants are suited to the treatment of joint and shaft fractures in children. These conclusions were drawn from clinical and experimental investigations at the University of Heidelberg. Since 1990 13 fractures, including 5 medial malleolus fractures, 2 retropatella flake fractures, 1 metacarpal fracture, 2 lateral condyle, 2 epicondyle fractures and a secondary dislocated forearm fracture were treated with BIOFIX pins. 11 of these cases were without complications. There was one case of infection, and due to material failure the stability was insufficient in one case. In a post-mortem study torsional fractures were produced in femora of children between 5 and 15 months. The fractures were then fixed with one resorbable screw and put under torsional loading until the bone refractured. The post-fixation force (torsional) amounted to 77% of the original fracture force, and the degree of rotation at fracture was post-fixation 84% of the original. The stability of bioresorbable screws in the treatment of femoral spiral fractures in children can therefore be confirmed.

A biomechanical study of bicycle helmets' effectiveness in childhood.

The authors present the results of a series of impact tests on pedal cycle helmets. 10 helmets were tested using a drop test under three different test conditions: Left frontal/temporal from 1 m, right frontal/temporal from 1.5 m and left occipital from 1 m. Impact force and the acceleration of the headform's centre of gravity in three axes were measured. As a result of the authors' field research on pedal cycle helmets in Australia the 1.5 m drop height was considered to be more representative of a "real" accident than the less severe 1 m height fall. The range of resultant maximal accelerations, 1 m drop height, was 81 g to 193 g; 1.5 m drop height 122 g to 209 g. In comparison a fall without helmet from 0.5 m produced a maximal resultant acceleration of 282 g. Head injury criteria values were for 1 m drops between 201 and 630; from 1.5 m 547 to 1078; and without helmet from 0.5 m 906. The individual helmets are compared on these figures and their merits discussed.

Does lateral bending lead to bowing fracture in an infantile lower arm?

In a postmortem study on 50 lower arms of fetuses of the 25th week of gestation and newborn we performed three-point bending experiments to find out the stability of the lower arm after bending to the resulting fracture. Lower arms with intact soft tissue show an elastic behavior when bent from the side until fracture occurs. Applying the loading deflection diagrams we could classify the fractures into three types which differ significantly by means of bending moment, maximal deflection per unit length, and force required.

Liver and spleen ruptures in authentic car-to-car side collisions with main impact at front door or B-pillar.

Seventy-nine belt-protected front seat occupants sustained authentic car-to-car side collisions with impact at front door or B-pillar in which energy equivalent speed (EES) and delta V had a highly significant influence on the occurrence of liver and spleen ruptures. From an EES greater than or equal to 40 km/h the risk of suffering liver and spleen injuries proved to be much higher for occupants on the impact side. Drivers on the impact side often had combined liver and spleen ruptures, front seat passengers had only liver ruptures and combined liver and spleen ruptures. The number of rib fractures on the left or right had a highly significant influence on the occurrence of liver and spleen ruptures. Liver ruptures and combined liver and spleen ruptures were often combined with pelvic ruptures.

Technical parameters influencing the severity of injury of front-seat, belt-protected car passengers on the impact side in car-to-car side collisions with the main impact between the front and rear seats (B-pillars).

Authentic car-to-car side collisions (n = 30) with the main impact area at the B-pillar were analyzed to find technical parameters corresponding with the injury severities of the front seat, belt-protected car passengers on the impact side. EES (Energy Equivalent Speed) and delta v (delta v, change in velocity) were highly significant predictors of the severity of thoracic and abdominal injuries and total injury severity coded according to the Abbreviated Injury Scale (AIS). At an EES or delta v greater than or equal to 40 km/h all front-seat car passengers on the impact side sustained a total injury severity of Maximum AIS (MAIS) greater than or equal to 4 and died. Although a passenger could survive the crash without injury to one or more body regions up to the highest EES- and delta v-values, at EES or delta v greater than or equal to 40 km/h fatal injuries were sustained in at least one body region. At an EES greater than or equal to 35 km/h or a delta v greater than or equal to 15 km/h no front-seat car passenger on the impact side remained uninjured.

[Injuries caused by automobile safety glass]. / Verletzungen durch Auto-Sicherheitsglas.

The report initially discuss the properties and application of tempered glass (TG) and laminated glass (LG) in motor vehicles. Although the trunk and extremities are injured these injuries are seldom life threatening. In contrast, head or neck injuries present a greater threat to life. Especially serious are TG injuries resulting in blindness. The resultant vehicle damage can appear not only as isolated glass cracking, which occurs regularly accompanying injuries without loss of consciousness, but as deformation of the vehicle interior adjacent to the windscreen. In the cases where more solid structures are impacted fatal injuries are possible. This report presents detail both of some real accident investigations and of 9 simulated oblique collisions using 9 post mortem human subjects (PMHS's). In these 9 simulations the head impacted during the primary impact phase against side windows constructed from TG. A modified tempered glass construction (two plates sandwiching a 3 mm air layer) was also tested. Impact angles were 35 to 45 degrees. The severity of facial laceration was dependent on collision severity, type of glass and glass damage resulting from head impact. Minor or severe cutting injuries of the face were caused. Only through the investigation of real accidents and accident simulations can occupant safety be improved.

[Injuries of the occipital condyles in fatal traffic accidents]. / Verletzungen der Schädelbasiscondylen bei tödlichen Strassenverkehrsunfällen.

Among 600 deaths of traffic accidents we found injuries of the occipital condyles in 10 cyclists, 12 car drivers and 3 pedestrians. In most cases the collision speed ranged from 70 to 100 km/h. In 18 cases of direct head impact the more severe injury was on the opposite side, in 4 cases of indirect side impact (whiplash injury) on the same side. Most types of fractures were 12 horizontal disconnections and 4 fractures of the inner edges. In 9 cases the condyle fractures were on one side, in 16 cases on both sides.

[Roentgenologic heart volume determination for the diagnosis of fatal heart failure]. / Die röntgenologische Herzvolumenbestimmung zur Diagnose des tödlichen Herzversagens.

In order to investigate the connection between the cardiac volume and the cardiac shadow plane, 385 anterior-posterior radiographs of the thorax have been selected comparing their cardiac shadow plane with the corresponding cardiac volumes determined by the autopsy of the cadavers. The comparison showed a connection of both magnitudes by means of the formula Hvol = 0.49 x Fa x square root of Fa (Hvol = cardiac volume in cm3, Fa = cardiac shadow plane of the anterior-posterior radiograph in cm2, corrections were made from the radiation divergence). A verification of the formula showed a very high correlation (r = 0.984) in 25 cadavers to be dissected. The comparing volume of the cardiac shadow plane has been investigated by means of the water displacement method, in which the cardiac vessels were ligated and the heart taken out of the cadaver. The cardiac volume, evaluated from the cardiac shadow plane showed a significant correlation at the cardiac death by internal natural cause. The comparison of the mathematical evaluated cardiac blood volumes of the symptoms causing death showed that the cardiac blood volumes in the group of poisonings and the group of drowning, suffocations and hanging with 231 ml and 211 ml in the men collective were at the same level as the cardiac death (246 ml). About the same applied to the women collective.(ABSTRACT TRUNCATED AT 250 WORDS)

[Quasi-static and dynamic bending stress of the pediatric femur for producing a femoral fracture]. / Quasistatische und dynamische Biegebelastung des kindlichen Oberschenkels zur Erzeugung einer Femurfraktur.

At the Institute of Forensic Medicine of the University of Heidelberg, in the years 1986-1988 thigh loading tests were conducted in order to produce fractures in a total of 28 cadavers of babies and children who had died at ages ranging from 1 day to 6 years. In 18 tests a universal strength testing machine was used and each thigh was loaded quasi-statically from the outside with a blunt edge applied to the middle of the femur, bending it to the point of fracture. The loading velocity amounted 50 mm/min with a defined support distance. The breakage load amounted to 470 N in a 6-day-old baby and increased about evenly up to 2920 N in a 6-year-old child; however, in a newborn 2720 N was needed and in a 15-month-old child, 5700 N. The total deformation way ranged from 16 to 60 mm. The main types of fracture that occurred were: complete and incomplete transverse fractures, oblique fractures, Messerer fractures, and spongiosa fractures. Ten children ranging in age from 2 months up to 27 months were submitted to dynamical thigh loading by means of a failing weight impactor and a horizontal impactor. Only in one case did a transverse fracture occur, when the lateral thigh impacted on an edge at a falling height of 70-93 cm. The forces set up amounted to 320-600 N with the falling weight impactor and to 2370 N with the horizontal impactor. These results suggest that fracture of the femur does not occur if a baby or small child falls from a changing table or from an adult's arm.