In this study of a cohort of conservatively treated patients with a low-energy pelvic ring fracture, we could demonstrate a relation of three specific fracture characteristics, namely horizontal sacral fractures, comminuted ventral fractures and dislocated ventral fracture, with overall survival. In contrast, the extent of the fracture (absent, unilateral, bilateral) in the dorsal or ventral ring was not associated with overall survival.
Previously a significant difference in survival of elderly patients with AO type A compared to AO type B pelvic fractures after low-energy trauma with 80% of conservative treatment has been reported . In contrast, the categories of the FFP classification have neither in our population nor in a previous study been reported to be associated with survival or mortality . Also, the alphanumeric classification by Krappinger et al has not yet been reported to correlate to outcome measures .
Our results suggest that specific aspects of the dorsal as well as ventral fracture seem to have an impact on survival and it might therefore be favourable to take these into account in future decision-making regarding treatment options for these patients. These three specific aspects of pelvic fractures in the elderly seem to have a higher impact than the extent of dorsal or ventral fractures. Horizontal sacral fractures are most frequently associated with an H-type fracture pattern that often triggers surgical stabilisation, so the unfavourable prognosis associated with horizontal sacral fractures may by already taken into account. In contrast, the impact of comminuted and dislocated anterior fractures on mortality might reflect a so far underestimated functional impact of fractures in the ventral pelvic ring.
A stratification according to patients’ risk reveals further insight. Horizontal sacral fractures were found to be particularly harmful in low-risk patients, whereas comminuted and dislocated ventral fractures proved more harmful in high-risk patients with a significant increase in mortality in these patients. This differential impact of the dorsal vs anterior fracture characteristic in distinctly different populations of elderly patients is somewhat surprising. In general, high-risk patients are characterized in our population by a substantial short-term mortality (25% mortality within the first six months), whereas low risk patients are characterized by a slow long-term decline. As visible in Figure 5, in frail, high risk patients, comminuted or dislocated ventral fractures seem to increase the short-term mortality, whereas horizontal sacral fracture do not show this effect. In contrast, in fit, low risk patients, horizontal sacral fractures seem to have an unfavourable effect on the long-term decline. These findings suggest that interpretation of fracture characteristics with respect to decision making may have to take into account the degree of frailty of the patients.
In line with this interpretation the impact of fracture characteristics on mortality seems to be smaller compared to patient characteristics. Age, existing decreased mobility, and comorbidities are directly associated with an increased mortality risk. The same tendency was observed for patient characteristics that did not directly and statistically relevantly correlate with mortality, ie. living situation, use of walking aid and PMS. The lack of significance can be explained by the fact that these three all tend to measure the same concept, namely the degree of mobility and as consequence independence in daily living. Indeed, if added as single variables to a base model with age, gender and comorbidity as covariates, they always resulted in a statistically significant effect. These findings underline the frailty of this specific patient group and the vital importance of mobility .
Treatment strategies for pelvic fragility fractures are not yet well established [2, 23, 26]. Results for relevant outcomes have been reported for patients treated either conservatively or operatively, but are still somewhat ambiguous. Höch et al. report improved survival for operatively treated patients . Osterhoff et al. on the other hand reported an early protective effect of the non-operative treatment . One-year mortality after surgical fracture stabilisation has been reported between 10-28% [20, 29].
We reported only on conservatively treated patients. The restriction of this analysis to conservatively treated patients avoids an undesirable effect of surgery as a confounding factor. Surgery can unpredictably impact outcome and survival in both directions with a potential improvement, but also with a potential deterioration due to postoperative complications and surgery-related morbidity. Operatively treated patients with a pelvic fragility fracture might represent a selected subpopulation. However, even if the decision for surgery depends directly on the fracture characteristics, this does not bias the estimation of the effect of the prognostic value of these factors .
In addition, the analysis of conservatively treated patients allows to discuss possible adaptations of current practice and specific analyses of potentially underserved subpopulations.
The majority of our population was independently mobile and living prior to fracture diagnosis. Almost a quarter of this conservatively treated population further presented with a FFP type III or IV. Furthermore, treatment strategies generally aim at restoring baseline mobility and independence, thus first evaluating the success of conservative treatment.
We acknowledge the limitations of our study. First, it is a retrospective analysis. As follow up information was restricted to survival, data could nevertheless reliably be obtained for almost all patients using official records. Nevertheless, using overall survival as measure probably allows only to have a look at the tip of the iceberg with the true triggers and points of possible interventions hidden. Rigorous follow-up assessments with respect to mobility and quality of life may produce better insights into the association with patient relevant outcomes.