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This study investigated the mechanisms of traumatic rupture of the aorta (TRA). Eight unembalmed human cadavers were tested using various dynamic blunt loading modes. Impacts were conducted using a 32-kg impactor with a 152-mm face, and high-speed seatbelt pretensioners. High-speed biplane x-ray was used to visualize aortic motion within the mediastinum, and to measure deformation of the aorta. An axillary thoracotomy approach was used to access the peri-isthmic region to place radiopaque markers on the aorta. The cadavers were inverted for testing. Clinically relevant TRA was observed in seven of the tests. Peak average longitudinal Lagrange strain was 0.644, with the average peak for all tests being 0.208 ± 0.216. Peak intraluminal pressure of 165 kPa was recorded. Longitudinal stretch of the aorta was found to be a principal component of injury causation. Stretch of the aorta was generated by thoracic deformation, which is required for injury to occur.

For more than 20 years, field research and laboratory testing has consistently demonstrated that wearing a seat belt dramatically reduces the risk of occupant death or serious injury in motor vehicle crashes [1, 2]. The injury prevention benefits of seat belts require that they remain fastened during collisions. Federal Motor Vehicle Safety Standards set forth seat belt buckle performance requirements to address buckle performance in accident conditions. However, several theories of buckle release or separation exist including: false latch, inadvertent release, and inertial release. Forensic investigations of vehicle crashes would benefit with diagnostic criteria which could distinguish between a buckle separation, a properly restrained occupant, and an unused or stowed seat belt. In the unlikely event of buckle separation, entanglement with the webbing would be expected if the occupant moves substantially as a result of the crash forces.

A biaxial test device was designed to obtain the material properties of aortic tissue at rates consistent with those seen in automotive impact. Fundamental to the design are four small tissue clamps used to grasp the ends of the tissue sample. The applied load at each clamp is determined using subminiature load cells in conjunction with miniature accelerometers for inertial compensation. Four lightweight carriages serve as mounting points for each clamp. The carriages ride on linear shafts, and are equipped with low-friction bearings. Each carriage is connected to the top of a central drive disk by a rigid link. A fifth carriage, also connected to the drive disk by a rigid link, is attached at the bottom. A pneumatic cylinder attached to the lower carriage initiates rotation of the disk. This produces identical motion of the upper carriages in four directions away from the disk center.

In the mid 1970s, UMTRI investigated the biomechanical properties of the head and neck using 180 “normal” adult subjects selected to fill eighteen subject groups based on age (young, mid-aged, older), gender, and stature (short, medium, and tall by gender). Lateral-view radiographs of the subjects’ cervical spines and heads were taken with the subjects seated in a simulated automotive neutral posture, as well as with their necks in full-voluntary flexion and full-voluntary extension. Although the cervical spine and lower head geometry were previously measured manually and documented, new technologies have enabled computer digitization of the scanned x-ray images and a more comprehensive and detailed analysis of the variation in cervical spine and lower head geometry with subject age, stature, and gender. After scanning the radiographic images, 108 skeletal landmarks on the cervical vertebrae and 10 head landmarks were digitized.

The adult head has been studied extensively and computationally modeled for impact, however there have been few studies that attempt to quantify the mechanical properties of the pediatric skull. Likewise, little documentation of pediatric anthropometry exists. We hypothesize that the properties of the human pediatric skull differ from the human adult skull and exhibit viscoelastic structural properties. Quasi-static and dynamic compression tests were performed using the whole head of three human neonate specimens (ages 1 to 11 days old). Whole head compression tests were performed in a MTS servo-hydraulic actuator. Testing was conducted using nondestructive quasi-static, and constant velocity protocols in the anterior-posterior and right-left directions. In addition, the pediatric head specimens were dropped from 15cm and 30cm and impact force-time histories were measured for five different locations: vertex, occiput, forehead, right and left parietal region.

Unlike other modes of loading, the tolerance of the human neck in tension depends heavily on the load bearing capabilities of the muscles of the neck. Because of limitations in animal models, human cadaver, and volunteer studies, computational modeling of the cervical spine is the best way to understand the influence of muscle on whole neck tolerance to tension. Muscle forces are a function of the muscle's geometry, constitutive properties, and state of activation. To generate biofidelic responses for muscle, we obtained accurate three-dimensional muscle geometry for 23 pairs of cervical muscles from a combination of human cadaver dissection and 50th percentile male human volunteer magnetic resonance imaging and incorporated those muscles into a computational model of the ligamentous spine that has been previously validated against human cadaver studies.

Based on an analysis of the National Automotive Sampling System (NASS) database from calendar years 1995-2000, over 30,000 fractures and dislocations of the knee-thigh-hip (KTH) complex occur in frontal motor-vehicle crashes each year in the United States. This analysis also shows that the risk of hip injury is generally higher than the risks of knee and thigh injuries in frontal crashes, that hip injuries are occurring to adult occupants of all ages, and that most hip injuries occur at crash severities that are equal to, or less than, those used in FMVSS 208 and NCAP testing. Because previous biomechanical research produced mostly knee or distal femur injuries, and because knee and femur injuries were frequently documented in early crash investigation data, the femur has traditionally been viewed as the weakest part of the KTH complex.

Tensile neck injuries are amongst the most serious cervical injuries. However, because neither reliable human cervical tensile tolerance data nor tensile structural data are currently available, the quantification of tensile injury risk is limited. The purpose of this study is to provide previously unavailable kinetic and tolerance data for the ligamentous cervical spine and determine the effect of neck muscle on tensile load response and tolerance. Using six male human cadaver specimens, isolated ligamentous cervical spine tests (occiput - T1) were conducted to quantify the significant differences in kinetics due to head end condition and anteroposterior eccentricity of the tensile load. The spine was then separated into motion segments for tension failure testing. The upper cervical spine tolerance of 2400 ± 270 N (occiput- C2) was found to be significantly greater (p< 0.01) than the lower cervical spine tolerance of 1780 ± 230 N (C4-C5 and C6-C7 segments).

Investigators currently lack the data necessary to define the state of skeletal muscle properties within the cadaver. The purpose of this study is to define the temporal changes in the postmortem properties of skeletal muscle as a function of mechanical loading and freezer storage. The tibialis anterior of the New Zealand White rabbit was chosen for study. Modulus and no-load strain were found to vary significantly from live after eight hours postmortem. Following the dynamic changes which occur at the onset and during rigor mortis, a semi-stable region of postmortem, post-rigor properties occurred between 36 to 72 hours postmortem. A freeze-thaw process was not found to have a significant effect on the post-rigor response. The first loading cycle response of post-rigor muscle was unrepeatable but stiffer than live passive muscle.

The absence of constitutive data on muscle has limited the development of models of cervical spinal dynamics and our understanding of the forces developed in the cervical spine during impact injury. Therefore, the purpose of this study is to characterize the structural and material properties of skeletal muscle. The structural responses of the tibialis anterior of the rabbit were characterized in the passive state using the quasi-linear theory of viscoelasticity (r = 0.931 ± 0.032). In passive muscle, the average modulus at 20% strain was 1.75 ± 1.18, 2.45 ± 0.80, and 2.79 ± 0.67 MPa at test rates of 4, 40, and 100 cm·s-1, respectively. In stimulated muscle, the mean initial stress was 0.44 ± 0.15 MPa and the average modulus was 0.97 ± 0.34 MPa. These data define a corridor of responses of skeletal muscle during injury, and are in a form suitable for incorporation into computational models of cervical spinal dynamics.