Lap-belt Injury

There may be dislocation of the facet joints in lap belt injuries. This can be seen as widening, superior subluxation, perching or locking of the facets. Facet malalignment is best appreciated on CT reconstructions. Rotatory stability of the thoracolumbar spine is provided by the facet joints and these are injured in significant fracture dislocations caused by combined flexion and rotation. The major hallmark of fracture dislocation type of injuries is intervertebral subluxation or dislocation. 

The Hybrid III dummy was the first to demonstrate humanlike chest responses typical of the biomechanical data for frontal impacts [Foster et al., 1977]. Rouhana [1989] developed a frangible abdomen, useful in predicting injury for lap-belt submarining. More recent work by Schneider et al. [1992] led to a new prototype frontal dummy. Lateral impact tests of cadavers against a rigid wall and blunt pendulum led to side-impact dummies, such as the Eurosid and Biosid [Mertz, 1993]. Even more recently, a small female-sized side-impact dummy has been developed [Scherer et al., 1998]. 

We can define restraints as any manual method, physical device, or mechanical device used to restrict the freedom of movement or normal access to one s body. Due to an increasing number of reports of injury and death associated with the incorrect use of patient restraints, the FDA warns health professionals to ensure the safe use of these devices. Restraints can include safety vests, lap belts, wheelchair belts, and body holders. Incorrect use of these devices has involved using the... 

One device that has reduced injuries from the second crash and saved lives is the seat belt. Seat belts became mandatory in 1968. Initially there was only a lap belt. By the 1980s a combined lap belt and shoulder harness became the standard. Eventually, lap belts expanded to rear seats. The combined lap belt and shoulder harness eventually became the standard for rear seats. The belt designs fit adults. Infant and child seats slowly evolved so that adult belts served as the primary restraints for them. Additional belts systems in child seats provided restraint to the seat for a child. 

Active restraints are oecupant restraints that are effective only if the driver activates fiiem. The prime example is seat belt. By far the greatest contributor to injury reduction in file past few decades is the occupants use of seat belts. The current retracting three-point seat belt provides much more protection than the early fixed lap belts. But despite their proven effectiveness, some drivers and passengers are still reluctant to use them. 

Figure 10-7, The risk of injury without restraints, with inappropriate restraints, and with appropriate restraints. Inappropriate restraints were belts for 4-8 years old children and lap belt only or shoulder belt only for 9-15 years old children (from Durbin et al., 2005, with permission of the American Academy of Pediatrics).

The first independent attempt to estimate conventionally the benefits and costs of mandatory passive restraints was made by Richard Amould and Henry Grabowski. For the reduction in fatalities and injuries in crashes they use two sets of estimates. One set is based on a 1981 field team study of rural traffic accidents which shows, for example that fatalities are reduced by 34 percent by air bags and lap belts together, 32 percent by lap and shoulder belts together, 28 percent by passive belts, and 25 percent by air bags alone. The field study estimates are only appronmately one half of the NHTSA lab study estimates which is the other set. Arnould and Grabowski assume that 60 to 70 percent of occupants with passive belts would use them and that 0 to 20 percent of occupants with air bags would also use lap belts. Occupant protection is assumed to have no affect on chances of accidents. The 1 5 distribution of traffic accident injuries and the estimates of restraint effectiveness in crashes are used to calculate the fatalities and injuries prevented. 

Since 1998 aU cars sold in the United States have heen required to have driver and passenger air bags. Research by the U.S. Department of Transportation shows that air bags reduce the risk of death in a frontal collision by about 30%. An air bag plus wearing lap and shoulder belts reduces the likelihood of moderate injury in front-end crashes by about 60%. 

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