Risk factors affecting pulmonary complications in elderly patients with isolated rib fractures

Introduction

As the global aging trend intensifies, the number of elderly trauma patients is increasing rapidly, posing substantial challenges to public health and healthcare systems. According to the National Bureau of Statistics of China, the population aged 65 years and older increased from 145.24 million in 2015 to 210.35 million in 2022 (1), with this trend anticipated to persist. This demographic shift has resulted in a notable increase in the proportion of older individuals in trauma centers (2), particularly following chest injuries, and a marked rise in the incidence of rib fractures (3).

Rib fractures are believed to be the most common injury following blunt chest trauma (4,5), affecting up to two-thirds of patients (6), and can lead to severe complications such as pneumothorax, hemothorax, and lung contusion. Studies have demonstrated that age (7), the number of rib fractures (8), and displacement are closely associated with the incidence of pulmonary complications (9-11). In China, there are approximately 1.5 to 2 million rib fractures annually (12), which exceeds the incidence of lung tumors (0.7 million) (13), underscoring the public health significance of rib fractures.

Although studies have explored the relationship between rib fractures and pulmonary complications (14,15), many have not excluded patients with other serious concomitant injuries, leading to limited results. Additionally, research on the relationship between rib fracture patterns and trauma mechanisms following chest injuries remains scarce (16). Therefore, this study focuses on analyzing elderly patients with isolated rib fractures, and explores the relationship between trauma mechanisms, fracture patterns, and pulmonary complications to inform better clinical treatment strategies.

Objectives

This study aims to describe the incidence of pulmonary complications in elderly patients with isolated rib fractures, identify the risk factors associated with these complications, and investigate the impact of trauma mechanisms and fracture patterns on the occurrence of pulmonary complications. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1323/rc).

Methods

Data source

We retrospectively analyzed all trauma patients admitted to Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University from January 2015 to December 2019. Using the hospital’s medical record management system, we reviewed and verified relevant imaging data and nursing records, and selected study subjects based on inclusion and exclusion criteria. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Institutional Review Board of Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University (No. KL20240140), and individual consent for this retrospective analysis was waived. We utilized diagnostic and procedural codes from the Tenth Revision of the International Classification of Diseases (ICD-10) (17) (Table S1), to establish and define specific variables in this study.

Patient selection

This study included all patients aged 65 and older with rib fractures diagnosed by computed tomography (CT) or three-dimensional CT (3D CT) due to blunt thoracic trauma. We excluded patients with old rib fractures or suspected rib fractures confirmed by 3D CT or further radiology examination. Many elderly patients with rib fractures often suffer from severe injuries to anatomical regions other than the chest, or undergo invasive surgical procedures, such as craniocerebral injuries and limb fractures requiring surgery. These injuries or procedures may significantly impact the patient’s pulmonary complications and other adverse outcomes. Therefore, we also excluded the following patients: those requiring invasive procedures or surgery in anatomical areas other than the chest, those who died within 24 hours of admission, and those with an Abbreviated Injury Scale (AIS) score ≥3 in any of the following regions: Head & Neck, Face, Abdomen, Extremities, or External areas. Additionally, to ensure data consistency and accuracy, we excluded patients with unclear injury mechanisms, those who were discharged against medical advice or abandoned treatment for various reasons, those with incomplete case data, or those transferred from another hospital who received medical care for more than 24 hours.

Variables and study design

We extracted clinical data from electronic medical records, which primarily included demographic information (gender, age, marital status, comorbidities), trauma mechanisms, hospitalization costs, details of traumatic, surgeries, length of stay (LOS), complications (pneumothorax, hemothorax, pneumonia, pulmonary contusion, respiratory failure, atelectasis, deep vein thrombosis), and AIS scores. Additionally, we separately calculated the Thorax Abbreviated Injury Scale (AIS_Thorax) and the RibScore (18) (Table S2). We collected the following comorbidities: diabetes, coronary heart disease (CHD), cerebral infarction, chronic obstructive pulmonary disease (COPD) and hypertension.

Isolated rib fractures are defined as rib fractures resulting from blunt thoracic trauma with an AIS score of less than 3 for any non-thoracic region (19). Hemothorax is defined as the presence of fluid in the pleural cavity on chest CT in trauma patients, diagnosed unless proven otherwise (20). The diagnosis of respiratory failure is primarily based on arterial blood gas analysis; It is diagnosed when there are clinical symptoms such as dyspnea and the PaO₂ is found to be <8 kPa (60 mm Hg). The number of rib fractures and the count of displaced rib fractures were assessed by two researchers based on imaging reports and measurements. In cases of disagreement, consensus was reached through discussion, with the final result being the agreed conclusion.

The trauma mechanisms were categorized into four groups: motor vehicle crash (e.g., pedestrian and motor vehicle collision, motor vehicle and motor vehicle/non-motor vehicle collision), non-motor vehicle (bicycle or electric bicycle) crash (e.g., pedestrian and non-motor vehicle collision, non-motor workshop collision), falls, and others (e.g., assaults, impacts from falling objects). Based on age, elderly patients are divided into two groups: 65–74 years old and ≥75 years old. Rib fractures are classified as follows: (I) displacement [a displaced rib fracture is defined as a displacement distance of at least half the width of the rib (10)] group and non-displaced group; (II) single rib fracture group and multiple rib fractures (≥2 ribs) group; (III) flail chest group and non-flail group. Finally, the morbidity will be analyzed for each group.

Outcomes

The primary outcome variables of the study are pulmonary complications, including pneumothorax, hemothorax, pneumonia, atelectasis, pulmonary, and respiratory failure. The secondary outcome is mortality.

Statistical analysis

Data were analyzed using SPSS (version 25.0; SPSS, Chicago, IL, USA). Initially, normality was assessed using the Shapiro-Wilk test, and quantitative data not conforming to normal distribution were expressed as median (M) with interquartile range (IQR). Qualitative data were presented as percentages, and comparisons between groups were performed using Pearson’s χ² test or Fisher’s exact test. Independent sample non-parametric data were analyzed using the Mann-Whitney U test, and multiple samples were analyzed using the Kruskal-Wallis one-way analysis of variance (ANOVA) with Bonferroni correction. Multivariate logistic regression analysis was performed to identify risk factors for pulmonary complications, and regression analysis was conducted. Subgroup analysis was used to compare the relationship between different risk factors and various pulmonary complications. The Hosmer-Lemeshow test was employed to evaluate the goodness of fit of the model, with P<0.05 considered indicative of statistical significance.

Results

Between 2015 and 2019, 3,710 patients who were diagnosed with rib fractures following radiology examination were admitted to the center 1,223 of them were elderly patients aged 65 years or older. After excluding patients with concurrent injuries requiring invasive procedures and surgery, patients with old rib fractures, patients with AIS scores ≥3 in other regions besides the thoracic, and patients with data deformity, 168 patients were included in this study (Figure 1).

Figure 1 Flow chart of the study.

The median age of the 168 patients in this study was 72 years (IQR, 68 to 78 years). The oldest patient was 92 years old, and 61.9% of the patients were male (n=104). A total of 126 patients developed pulmonary complications, with no significant gender difference (P=0.14). Except for one patient who developed hemothorax and, despite undergoing surgical treatment, eventually died in the hospital due to pneumonia (mortality rate 0.6%), all other patients recovered and were discharged (Table 1). The largest proportion of fracture patterns reported were non-displaced rib fractures (n=91, 54.2%), multiple rib fractures (n=133, 79.2%), and non-flail chest (n=157, 93.5%). Regarding trauma mechanisms, motor vehicle crash accounted for the largest proportion (n=60, 35.7%), followed by falls (n=55, 32.7%), non-motor vehicle crash (n=41, 24.4%), and others (n=12, 7.1%) (Figure 2).

Figure 2 Distribution of mechanisms. MVC, motor vehicle crash; N-MVC, non-motor vehicle crash.

Univariate analysis revealed that at P<0.1, age (P=0.052), trauma mechanisms (P<0.001), number of rib fractures (P<0.001), and fracture patterns (P<0.05) might be risk factors for pulmonary complications. Five factors, including age, trauma mechanisms, fracture patterns, diabetes, and COPD, were included in the multivariate Logistic regression model (Table 2). Following multicollinearity testing, results indicated that the Variance Inflation Factor (VIF) was less than 5, suggesting the absence of multicollinearity (Table S3), thereby confirming no significant correlation among these five independent variables.

Logistic regression including age, trauma mechanisms, fracture patterns, diabetes, and COPD showed that falls [odds ratio (OR) 5.051, 95% confidence interval (CI): 1.380–18.485; P=0.01], displaced rib fracture (OR 4.924, 95% CI: 1.826–13.275; P=0.002), and multiple rib fractures (OR 2.984, 95% CI: 1.182–7.531; P=0.02) were independent risk factors for pulmonary complications (Table 3). However, no association was found between age, COPD, or diabetes and pulmonary complications in elderly patients with isolated rib fractures (P>0.05) (Table 2).

Further subgroup analysis revealed that the elderly had a higher risk of hemothorax caused by falls, displaced rib fractures on imaging, and multiple rib fractures (respectively 85.5%, 89.6%, and 74.4%, P<0.05). When displaced rib fractures occurred, the incidence of atelectasis (41.6% vs. 23.1%, P=0.01), pneumothorax (41.6% vs. 9.9%, P<0.001), hemothorax (89.6% vs. 48.4%, P<0.001), and pulmonary contusion (26.0% vs. 7.7%, P=0.001) was higher than nondisplaced fractures group. When multiple rib fractures occurred, pneumothorax (28.6% vs. 8.6%, P=0.01) and hemothorax (74.4% vs. 40.0%, P<0.001) were more common than when single rib fractures occurred (Table 3).

Discussion

The main finding of our study was that traumatic mechanisms and fracture patterns were associated with pulmonary complications, particularly hemothorax, in elderly patients with isolated rib fractures. Whereas, we did not find a significant correlation between COPD, diabetes, age, and pulmonary complications of this population.

To date, the reported morbidity and mortality in elderly patients with rib fractures vary significantly across different studies. The Western Trauma Society Guidelines released in 2017 (4), reported a mortality rate of 10% for young adults, compared to at least 20% for those aged 65 years or older. The guidelines recommend that patients aged 65 years and older with more than two rib fractures be admitted to a unit providing intensive care services. A similar study also demonstrated high morbidity and mortality in patients with isolated rib fractures, of which the morbidity was up to 36% (21). However, other studies have pointed out that elderly patients with isolated chest injuries have a relatively low morbidity. Many patients who suffer from isolated, uncomplicated rib fractures, potentially lead to the overuse of intensive care unit (ICU) resources as these patients do not necessarily require treatment at a major trauma center (22,23). We believe this discrepancy is partly due to differences in patient populations. When additional injuries are excluded, the morbidity and mortality associated with rib fractures were significantly lower than that reported in the literature (19). Our study showed similar results: the mortality rate of isolated rib fractures in the elderly was low (0.6%). However, our research also indicates that elderly patients with isolated chest injuries have a high morbidity, up to 75%. Therefore, these patients still deserve our attention.

Morbidity and mortality associated with rib fractures escalate with the increasing number of fractures (14,24). A study has shown that when six or more ribs are fractured, the risk of death increases significantly (25). In elderly patients, fractures involving five or more ribs are significant predictors of poor prognostic outcomes (8). Our study also confirmed that the number of rib fractures (P<0.001) is an important predictor of pulmonary complications in elderly patients with isolated rib fractures. However, we found that multiple rib fractures were a risk factor for pulmonary complications, indicating a lower threshold for adverse outcomes in elderly patients.

In recent years, studies have suggested a possible connection between rib fracture patterns and pulmonary complications. A small retrospective study of 102 patients with blunt injuries found that those with midlateral rib fractures had the highest incidence of complications, with a 25% incidence of respiratory failure (26). Another retrospective study by Chien et al. showed that the number of displaced rib fractures is a good predictor of complications (10). Our study also shows that fracture patterns (displaced rib fracture, multiple rib fracture, flail chest) is a risk factor for pulmonary complications. However, to our knowledge, previous studies have not found a clear association between trauma mechanisms and pulmonary complications, especially in elderly patients with isolated rib fractures.

This study shows that rib fractures caused by falls, multiple rib fractures, and rib fracture displacement following chest injuries are important predictors of pulmonary complications in elderly patients. Specifically, these conditions are more likely to lead to hemothorax. A small volume of hemothorax can typically be absorbed completely; however, a larger volume can lead to complications such as compressive atelectasis, lung infections, respiratory failure, and hemorrhagic shock, often necessitating thoracic tube placement or surgical intervention. Interestingly, a recent study found that among elderly patients requiring surgery for chest injuries, falls exceeded traffic injuries (27), suggesting that chest injuries from falls are more severe or more likely to require surgery than other trauma mechanisms. However, it should be noted that the proportion of elderly people in this study was small and the overall sample size was limited. Notably, the only patient who died in our study sustained rib fractures and hemothorax following a fall, which led to pneumonia, respiratory and circulatory failure. Elderly people are more likely to experience falls than younger patients due to multiple medical comorbidities and age-related physiological decline (28). Our study further suggests that elderly patients who fall tend to have worse outcomes. In elderly patients with isolated rib fractures, falls are often due to intrinsic factors such as poor health and frailty, whereas other traumatic mechanisms like motor vehicle collision typically result from external factors. Patients involved in such accidents are more likely to have relatively better physical condition, enabling them to be outdoors rather than confined at home. This may explain why elderly patients who fall are more prone to developing pulmonary complications. However, this study did not find a relationship between multiple medical comorbidities (COPD, diabetes), age, and pulmonary complications. This may be attributed to the fact that elderly patients receive targeted treatment for comorbidities during hospitalization. Additionally, our study found that the occurrence of pulmonary complications often leads to increased medical costs [8.23 (4.98, 17.35) vs. 6.78 (3.83, 9.95) thousand CNY, P=0.02] (Table 1) and a higher likelihood of invasive procedures such as thoracostomy in this study [19 (100%) vs. 0 (0%), P=0.02] (Table 1).

A previous study has shown that the modified frailty index and RibScore are effective for predicting pulmonary complications from rib fractures (29), but these methods are time-consuming. In contrast, the trauma mechanisms and fracture patterns can be quickly obtained through medical history and initial radiological imaging. Therefore, our findings can assist busy emergency trauma physicians in swiftly identifying high-risk patients with isolated rib fractures who may develop pulmonary complications and in screening those who may require hospitalization.

Limitations

There are several limitations in this study. First, the retrospective nature of this study inevitably introduces selection and recall bias. Second, most data in this study come from our center’s medical record system. Due to variations in the quality of medical record documentation, some important information, such as underlying diseases, body mass index (BMI), may be missing. Third, this was a single-center retrospective study. Despite the substantial number of patients with blunt thoracic trauma, the final count of enrolled patients was limited after applying the inclusion criteria, thereby restricting the analysis of other rib fracture patterns. In summary, due to the limited sample size and retrospective nature of this study, some results should be interpreted with caution. Future research should involve multi-center, large-sample prospective studies.

Conclusions

A significant relationship exists between the mechanism of trauma, fracture patterns, and pulmonary complications (particularly hemothorax) in elderly patients with isolated rib fractures. Elderly patients who experience falls and exhibit radiographic findings of displaced or multiple rib fractures are at an increased risk of developing pulmonary complications. Therefore, heightened vigilance is essential concerning the elevated incidence of traumatic hemothorax and its potential consequences.

Acknowledgments

The authors would like to thank Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University for providing the research facilities.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1323/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1323/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1323/prf

Funding: The study was supposed by the Natural Science Foundation of Zhejiang Province (No. LTGY23H160028), and Medical Science and Technology Project of Zhejiang Province (No. 2023KY1311).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1323/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Institutional Review Board of Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University (No. KL20240140), and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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