Discussion

This study investigated the incidence and associated injury patterns of TAWH in a postmortem cohort, with a specific focus on MVOs. MVOs happen more frequently than train accidents and are more likely to be survived. Therefore, this patient group seems to be of the greatest interest. Studying this group in further detail and gaining an understanding of the associated injuries and injury patterns could help save lives. The primary finding is that the overall incidence of TAWH in fatal traffic accidents (20.6%) is substantially higher than the 0.17% to 1.5% reported in clinical series of surviving blunt trauma patients [9–11]. This suggests that TAWH may be an under-recognized marker of severe, often lethal, traumatic forces. The incidence was highest among pedestrians struck by trains (42.1%), further underscoring the association of TAWH with extreme high-energy impact mechanisms.

A key objective of this study was to investigate the relationship between TAWH and seatbelt use. While our results showed that all TAWHs with confirmed seatbelt status occurred in belted occupants (7 of 30), a definitive conclusion is precluded by significant data limitations. Seatbelt usage could only be confirmed in 47.2% of cases, and the non-seatbelted group was too small (n = 4) for meaningful statistical comparison. However, considering the high rates of seatbelt compliance in Germany—reported at 98.6% for drivers in 2023 [16]—it is highly probable that the majority of patients with undocumented status were, in fact, wearing seatbelts. This would imply that the actual incidence of TAWH in seatbelted occupants is likely higher than what our limited confirmed data shows. This finding aligns with the concept of the “seatbelt sign” and supports the theory that TAWH can result from a deceleration injury where the lap belt acts as a fulcrum, causing a sudden, massive increase in intra-abdominal pressure that leads to fascial and muscular rupture [10]. While TAWH has been reported in unrestrained occupants [3], our data suggests it may be a more characteristic injury in the restrained population.

The strong and statistically significant correlations between TAWH and other specific injuries provide compelling evidence for this proposed mechanism. The association with sternal and serial rib fractures (ϕ = 0.419, p < 0.001 and ϕ = 0.312, p = 0.008, respectively) points to significant force application across the chest by the shoulder portion of the seatbelt or the steering wheel. Chest compression in resuscitation was not a confounding factor. Concurrently, the correlation with lumbar transverse process fractures (right: p = 0.002, left: p = 0.003) and sacroiliac joint injuries (right: p < 0.001, left: p = 0.003) indicates massive force transmission through the lumbopelvic region, consistent with lap belt loading. Fractures of the transverse processes, in particular, can be caused by avulsion from forceful contraction of the quadratus lumborum muscle during violent hyperflexion over the lap belt. These injury patterns are characteristic of MVO trauma, as described by [6, 17], and their strong correlation with TAWH reinforces the mechanical link between the safety restraint, the resulting force vectors, and the observed abdominal wall failure.

The subgroup of MVO with TAWH was small, and reliable speed documentation was scarce. Therefore, no statistical analysis was performed, although the data suggests the potential for a meaningful analysis of a larger cohort, given that there were no rear-end collisions. In a larger cohort with well-documented speed and accident mechanisms, a correlation between TAWH and accident procedure seems possible. Another possible explanation for the lack of rear-end collisions is that this type of collision is less likely to be fatal than other types of collision [18].

It can be assumed with a high degree of probability that TAWH only occurred at high speeds within this small collective. However, since all of these accidents were fatal, a strong selection bias must be present within the overall collective.

In contrast to these strong mechanical correlations, demographic factors such as age and sex were not significantly associated with TAWH occurrence. A weak but statistically significant correlation with a higher BMI was noted in the overall traffic accident population (p = 0.049), but this was not a primary finding within the MVO subgroup analysis. This suggests that while pre-existing factors like a higher BMI might slightly increase susceptibility, the overwhelming determinant for TAWH is the nature and magnitude of the applied traumatic forces. Furthermore, our data showed no clear pattern linking the side of the hernia to the occupant’s seating position; for example, five of seven drivers presented with a right-sided hernia, which is counterintuitive if a simple interaction with the steering column were the cause. This complexity suggests that the injury mechanism is multifactorial, involving a combination of direct impact, seatbelt loading, and inertial forces.