Rib fracture timing in dynamic belt tests with human cadavers

Abstract

The purpose of this article is to present data from dynamic belt loading tests on the thorax of human cadavers where the exact timing of all rib fractures is known. To quantify rib fracture timing, a total of 47 strain gages were placed throughout the thorax of two human cadavers (one male, one female). To simulate thoracic loading observed in a severe car crash, a custom table-top belt loading device was developed. The belt loading pulse was configured to result in approximately 40% chest compression during a 150 ms load and unload cycle. The time histories of each strain gage were analyzed to determine the time of each rib fracture which was then directly compared with the reaction loads and chest displacements at that exact time, thereby creating a noncensored data set. In both cadavers, all rib fractures occurred within the first 35% compression of the thorax. As a general trend, fractures on the left side of the thorax, where the passenger belt passed over the abdomen, occurred first followed by fractures to the upper ribs on the right side of the thorax. By utilizing this technique, the exact timing of each injury level can be characterized relative to the mechanical parameters. For example, using rib fractures as the parameter for Abbreviated Injury Scale (AIS) scores in the female test, it was shown that AIS 1 injury occurred at a chest compression of 21.1%, AIS 2 at 21.6%, AIS 3 at 22.0%, and AIS 4 at 33.3%.

Reducing Chest Injuries in Automobile Collisions: Rib Fracture Timing and Implications for Thoracic Injury Criteria

“…In the current study, the effective stiffness values for the male and female PMHS thoraces were 13,619 and 11,189 (N/% compression), respectively. These values are consistent with the values reported by Kent et al 30 and Duma et al 11 Therefore, the use of a flat rigid back support does not appear to have a considerable influence on the effective stiffness of the thorax in frontal shoulder belt loading.…”

“…This is consistent with the findings of Duma et al, 11 who performed table-top shoulder belt loading with a flat rigid back support as opposed to the spine support bracket used in the current study. In addition, the bilateral rib fracture patterns observed in the current study were found to be consistent with those reported by Duma et al 11 Therefore, the use of a flat rigid back support does not appear to have a considerable influence on the overall deformation and injury response of the thorax in frontal shoulder belt loading.…”

“…Kent et al 30 and Duma et al 11 both performed table-top shoulder belt loading on PMHS thoraces, at a rate representative of that seen in a 48 km/h automotive collision, using a flat rigid back support and reported effective thoracic stiffness. Duma et al 11 reported the effective stiffness for one male and one female PMHS to be 19,449 and 6624 (N/% compression), respectively. Kent et al 30 reported that the effective stiffness for the five male tests varied from 7102 to 15,420 (N/% compression) and from 6459 to 9919 (N/% compression) for five female tests.…”

“…Single-axis strain gages aligned with the main axis of the rib were used because Duma et al 11 showed that the principal strain on the rib corresponded to the main axis of the rib during frontal shoulder belt loading. The right side of the thorax had strain gages located on the anterior regions of ribs 2-6 and on the lateral regions of ribs 3-7 (Figs.…”

“…11,25,33,47 There has only been one study to the authors' knowledge that has quantified rib fracture timing during frontal belt loading with the use of thoracic strain gages. 11 Duma et al 11 quantified rib fracture timing and corresponding injury timing during dynamic shoulder belt loading on PMHSs using a custom table-top belt loader with a flat rigid back support. However, Ali and Kent 1 noted that using a rigid flat back support in anterior-posterior thoracic loading could constrain the deformation and motion of the posterior region of the rib cage and limit the articulation of the costovertebral joints.…”