Severe pelvic injury: vascular lesions detected by ante- and post-mortem contrast medium-enhanced CT and associations with pelvic fractures

Pelvic fractures occur in 4–9.3% of patients with blunt trauma, and the prevalence of associated organ injuries ranges from 11 to 20.3%. [1, 2]. Pelvic haemorrhage is the most serious complication associated with pelvic fractures, and active haemorrhage remains the leading cause of death in polytrauma patients [2‐4]. Massive pelvic haemorrhage may originate from the branches of the iliac artery and/or major pelvic veins, from the small arteries running within the fractured bone or from the pelvic venous plexus [1, 5‐8].

In most emergency departments, polytrauma patients are initially evaluated by contrast medium-enhanced multi-detector computed tomography (MDCT) to detect active haemorrhage and enable immediate patient management and straightforward therapeutic decisions [2, 9, 10]. Detection of contrast medium extravasation on MDCT corresponds well to the site of bleeding seen on subsequent conventional angiography [1, 4, 9, 10] Furthermore, early detection of active bleeding by MDCT may lead to prompt angiographic embolisation. The latter has a technical success rate of up to 100%, with few complications, and it has been proven to be lifesaving [2, 4, 8, 11, 12]. Thus, immediate angiography and subsequent trans-catheter embolisation are currently accepted as the most effective methods for controlling arterial bleeding resulting from pelvic fractures [1, 8‐10, 13‐15]. However, little is known about the incidence and clinical significance of venous bleeding in these polytrauma patients. Moreover, no clinical series of polytrauma patients has directly correlated the bleeding sites with the underlying fractured pelvic bones.

The recent development of multi-phase post-mortem CT angiography (MPMCTA) has enabled the detection of vascular lesions in dead bodies, particularly those lesions present after severe trauma [16, 17]. Since the examination can be performed with a considerable volume of contrast agent injected at fast speed and with high pressure, MPMCT allows for the diagnosis of vessel injuries in great detail without disruption of nearby anatomical structures, unlike conventional autopsy. The technique was evaluated in a multi-centre study that included 500 autopsy cases, and it is the most widespread and best-investigated method for dead bodies [18].

Our objective in the present study was to investigate whether arterial or venous vascular lesions were responsible for contrast medium extravasation in blunt pelvic trauma victims. Furthermore, we explored whether the anatomical site of the vascular lesions corresponded with certain, well-defined patterns of pelvic fracture, since both are associated with the same kinetics due to underlying trauma.

We retrospectively included two different cohorts of severe blunt trauma victims who were referred to our hospital after an acute traffic accident, crush, or fall. They had all undergone contrast media-enhanced MDCT.

Our study showed that in blunt pelvic trauma, certain anatomical sites of arterial haemorrhage are associated with certain pelvic bone fractures. Indeed, in patients, we detected five correlations between arterial lesions and fractured pelvic bones (Table 3). In our post-mortem group, we observed seven artery-bone correlations. Moreover, MPMCTA revealed four associations between venous lesions and a fractured pelvic bone. To the best of our knowledge, anatomical correlations between bleeding sites and pelvic fractures have not been investigated previously in a consecutive clinical series of polytrauma patients neither in post-mortem cases. In the latter, Baqué et al. investigated the most frequent bleeding sites caused by pelvic open-book fractures [7]. The iliolumbar vessels were the most vulnerable pedicle in cases of sacroiliac joint disjunction [7] or iliac wing fracture [4] due to their anatomical relationship; this finding was confirmed by our statistically significant results.

In our patient group, the superior gluteal artery was the most frequently ruptured vessel, and there were also statistically significant associations between superior gluteal artery rupture and sacroiliac disjunction as well as sacral wing fracture, as previously reported [13, 24]. The second most frequently bleeding artery in our patients was the lateral sacral artery, which is typically injured after disruption of the posterior pelvic ring [13], including sacral wing fractures [4]; this finding was confirmed by our post-mortem results. Baqué et al. and Huittinen et al. considered the sacroiliac region the most important damage-prone pelvic area [6, 7], in agreement with our study, since sacral wing fracture was the most frequent type of pelvic fracture in both groups.

Additionally, bleeding of the lateral sacral artery occurred statistically more often in patients admitted for fall injuries, compared to patients presenting with traffic accidents or crushes. We explain this result by the mechanism inherent in most falls: The patients’ posterior pelvic ring is frequently the most vulnerable area of the body, since it is injured first and even with the highest force, when the patient after falling down hits the ground. In our post-mortem cases, we did not find this relationship, possibly due to the lower percentage of this mechanism of injury: only 11% (n = 24) of these cases were falls, unlike 49% (n = 24) in our polytrauma group.

The third most often injured artery in our patients was the obturator artery. This artery is known to typically bleed after acetabular or pubic rami fractures or symphysis disjunctions [4], which was again confirmed by our results.

Our study on post-mortem cases revealed that the number of injured arteries per body was significantly associated with the severity of pelvic ring fracture according to Tile classification. Despite a similar percentage of cases with pelvic fractures in both groups, we observed a higher number of Tile C fractures in the post-mortem cases than in living polytrauma patients (14 vs. 10) and, thus, a higher severity of pelvic fractures. This difference in fracture severity could explain the weaker association between vascular lesions and pelvic fractures we found in our patient group.

Using the Burgess and Young classification system for pelvic fractures, Dalal et al. and Magnussen et al. showed a clear association between the degree of pelvic ring disruption and vascular compromise [25] and consequent blood transfusion requirements [12]; however, they did not distinguish between venous and arterial bleeding. We used Tile classification instead of the classification system established by Young and Burgess. While both classifications differentiate between pelvic fractures according to the force vector that caused them, we think that the former is more straightforward and easier to apply [11, 20, 22].

Three types of bleeding may occur in severe pelvic fractures: arterial bleeding due to pelvic artery disruption, venous bleeding due to tearing or shearing of the pelvic veins and bleeding directly from fractured cancellous bone [5, 6, 8, 9]. In polytrauma patients, the haemodynamic consequences of venous bleeding after pelvic fractures are not well known, since they have been rarely reported. According to Baqué et al., in severe pelvic trauma, venous bleeding is more frequent than arterial haemorrhage, since venous walls are more fragile than the arterial walls. However, haemorrhages originating from venous dilacerations should be less serious than arterial bleeding because of the low blood pressure in the venous network. Due to pressure of the adjacent pelvic viscera, spontaneous haemostasis may occur [7].

In our group of polytrauma patients, we did not detect any actively bleeding veins, while we observed venous contrast extravasations in 35 out of our 45 post-mortem cases. The difference in the acquisition and injection parameters between our polytrauma MDCT and MPMCTA protocol is almost certainly responsible for this result, since we are convinced that venous lesions must have occurred in these severely injured patients. First, since the radiation exposure is not an issue when performing MPMCTA, unlike in polytrauma patients, we acquired four different acquisition phases in the post-mortem group. In our polytrauma patients, we performed a portovenous abdominopelvic acquisition only. Second, in cadavers, we used a far higher volume of contrast medium than in polytrauma patients [16, 19]. This difference may have had a definitive impact on the detection of arterial and venous lesions. Third, by using MPMCTA, the venous system is investigated separately from the arterial system. Injecting contrast media via a femoral venous cannula allows direct filling of the venous compartment without arterial filling. Finally, haemodynamically unstable polytrauma patients are in shock; therefore, their sympathetic nervous system is highly activated. Thus, consecutive vasoconstriction may prevent optimal contrast medium filling of the vessels and, consequently, decrease the degree of bleeding, seen as contrast media extravasation.

Comparing the diagnostic value of ante-mortem (MDCT) and post-mortem CT (MPMCTA) performed in eight trauma victims, Palmiere et al. reported higher sensitivity of MPMCTA for acute arterial or venous haemorrhage. Unfortunately, only one patient with pelvic injury was included [15] in this study.

Our study has several limitations, the most important of which is its retrospective design. The patients in the study had been investigated with a sole portovenous phase, according to our polytrauma protocol. Indeed, the portovenous or late phase has been proven to show contrast media extravasation with higher sensitivity and accuracy than the arterial phase [2, 9, 26‐28]. However, an additional arterial phase might have enabled diagnosis of any simultaneous venous bleeding located adjacent to an injured artery that had been overlooked, since in the present study, it could not be distinguished from nearby arterial bleeding on the basis of the venous phase only [9, 28].

A second limitation is that several correlations between vessels and fractured bone were significant for one side of the pelvis but not for the contralateral side; this is due to the limited number of patients and post-mortem cases that were included. Larger investigations should confirm the results for the contralateral side.

A third limitation is that we compared two different techniques of acquisition, MDCT and MPMCTA, by including two different population groups. Ideally, we would have compared the same subjects in an ante- vs. post-mortem approach. However, in our practice, MPMCTA is only realised for forensic issues. Thus, extremely few subjects are investigated by MDCT before and by MPMCTA after death. Furthermore, only ten of our polytrauma patients died from their accident, and none of them due to pelvic bleeding. In our original database, there was only one case, in which both examinations were performed: MDCT before and MPMCTA after death. However, since MPMCTA was performed after arterial embolisation, we had to exclude this case according to our inclusion criteria. In our post-mortem group, pelvic bleeding sources were lethal in only three cases (7%).

Finally, one could argue that some of the vessel injuries detected in our post-mortem group may correspond to post-mortem changes. However, the rapid fatal outcome of polytrauma victims without prolonged agony makes contrast extravasation due to decomposition of the bodies, which naturally occurs with time, extremely unlikely [29, 30].

In conclusion, we found that in the presence of severe blunt trauma pelvic injury, certain arterial and venous bleeding sites were significantly correlated with underlying pelvic fracture locations. In post-mortem cases, the number of arterial lesions depended significantly on the severity of the pelvic fracture. Venous bleeding was only visible post-mortem, unlike in polytrauma patients, which we attribute to the difference in acquisition parameters used. Therefore, not only arterial bleeding but also venous lesions contribute to severe pelvic haemorrhage, supporting the hypothesis that the importance of pelvic venous bleeding is underestimated in patients. Future investigations should evaluate the proportional contribution of venous bleeding to overall pelvic haemorrhage as well as its clinical significance.