Rib fixation in patients with severe rib fractures and pulmonary contusions: Is it safe?

Pulmonary contusions have been considered a contra-indication to rib fixation. However, pulmonary contusions are not associated with worse rib fixation outcomes, and it might even be associated with better outcomes for patients with mild to moderate pulmonary contusions. #ssrf.

C hest wall trauma is prevalent and morbid. Rib fractures account for around 10% of all trauma admissions and are associated with increased mortality and morbidity, and decreased quality of life. [1][2][3][4][5][6] Severe rib fracture patterns are often accompanied by other injuries, especially pulmonary contusions. 7,8 Pulmonary contusions are documented in more than 50% of patients with a flail chest. 9 Pulmonary contusions have dynamic pathophysiology, which, depending on the extent of the injury, can lead to pneumonia, acute respiratory distress syndrome, and mortality. 8,10,11 Currently, chest computed tomography (CT) is the recommended diagnostic modality, since it is highly sensitive in diagnosing pulmonary contusions. 12,13 Because pulmonary contusions can vary in size and severity, dichotomously classifying the presence or absence of pulmonary contusions is insufficient to appreciate the extent of the injury. 14 Furthermore, the severity of the pulmonary contusions detected on CT scan can change radiographically over time, especially in the first hours after injury. 15,16 Surgical stabilization of rib fractures (SSRFs) is increasingly used in the management of patients with severe rib fractures. 17 Pulmonary contusions have traditionally been considered a relative contraindication to SSRF because the pulmonary morbidity is presumed to arise predominantly from the contusion as opposed to the rib fractures. [18][19][20] Moreover, pulmonary contusion may increase the risk of general anesthesia and SSRF. However, there is a paucity of published data specifically about SSRF concerning the presence and severity of pulmonary contusions.
This study aimed to evaluate the association between pulmonary contusion severity and outcomes after SSRF. We hypothesized that outcomes would be worse in patients who undergo SSRF compared with patients whose rib fractures are managed nonoperatively.

Setting and Study Population
We retrospectively analyzed trauma patients who were admitted with three or more displaced (≥50% cortical displacement on axial CT imaging) rib fractures or flail segment (two or more consecutive ribs with fractures in two or more locations) from our prospectively maintained database in a level 1 trauma center. We included adult (18 years

Variables
Clinical data were retrieved from the patient's medical records, including age, sex, past medical history, time and mechanism of injury, Abbreviated Injury Scale (AIS) score and Injury Severity Score (ISS), injury characteristics, and surgical procedures. Similarly, clinical outcomes were retrieved. The primary outcome variable studied was pneumonia rate. Secondary outcomes included rates of tracheostomy, mortality, mechanical ventilation days, and intensive care and hospital length of stay. All patients requiring mechanical ventilation were placed on a standard protocol including lung protective (6-8 mL/kg ideal weight) ventilation. Patients with severe head injury as defined by head AIS score of >3 were excluded from the analysis evaluating the tracheostomy rate. Patients were evaluated on the admission chest CT for the presence of hemothorax, pneumothorax, bilateral rib fractures, flail segment, the total number of rib fractures, RibScore, and fracture displacement (undisplaced, offset, displaced) as defined by the Chest Wall Injury Society taxonomy. 21,22

Pulmonary Contusions
The presence and severity of pulmonary contusions were evaluated on the admission chest CT in axial and coronal views in the lung window on a maximum slice thickness of 3.5 mm. Pulmonary contusion severity was quantified using the Blunt Pulmonary Contusion 18 (BPC18) score. 15 In this score, the lung fields are divided into an upper, middle, and lower third, and for each third, a score of 1 to 3 was assigned. A score of 1 corresponds with mild contusion with up to 33% opacification of the field, a score of 2 is a moderate contusion with 33% to 66% opacification, and a score of 3 corresponds to severe contusion with more than 66% opacification. The scores are summed, resulting in a maximum score of nine per lung, and a maximum total score of 18. All chest CTs were reviewed independently for BPC18 by at least two observers. One of the observers was a physician who reviewed and scored all chest CTs. The second independent BPC18 score was assigned either by another physician or a research coordinator who was trained by the other physicians to score BPC18. Cases with more than 3 points difference were reviewed again within the research team to reach consensus on the score. The BPC18 score assigned by the observer who scored all chest CTs was used when discrepancies of less than three points occurred. Pulmonary contusion severity was defined as mild with BPC18 scores of 1 to 3, moderate with 4 to 6, and severe with 7 to 18. An example of a mild, moderate, and severe pulmonary contusion is shown in Figure 1.

Statistical Analysis
Data were analyzed using the Statistical Package for the Social Sciences version 28 (SPSS, Chicago, IL). The normality
Pulmonary contusion severity as expressed by BPC18 was associated with a higher likelihood of pneumonia (odds ratio [ Differences were found in outcomes for SSRF compared with nonoperatively managed patients, stratified for pulmonary contusion severity (Table 2). Surgical stabilization of rib fracture patients with mild pulmonary contusions had better respiratory outcomes and needed fewer ICU days, compared with patients who underwent nonoperative management. Surgical stabilization of rib fracture patients with moderate pulmonary contusions had fewer mechanical ventilation days compared with patients who underwent nonoperative management. No differences in outcomes were found between SSRF patients and nonoperatively managed patients when they had severe pulmonary contusions.
To evaluate the association between SSRF and outcomes, we adjusted for injury severity using regression analyses (Table 3). These multivariable regressions indicated that, after adjusting for injury severity, SSRF patients with mild pulmonary contusions had a shorter stay in the ICU compared with nonoperatively managed patients with mild contusions (adjusted β, −2.51 [95% CI, −4.87 to −0.16]). Similarly, after adjustment, SSRF patients with moderate pulmonary contusions had fewer days on mechanical ventilation (adjusted β, −5.19 [95% CI, −10.2 to −0.17]) compared with nonoperatively managed patients with moderate pulmonary contusions. In the adjusted analyses for patients with severe pulmonary contusions, no differences in in-hospital outcomes were found between SSRF versus nonoperatively managed patients.

DISCUSSION
This study aimed to evaluate the association between pulmonary contusion severity and outcomes after SSRF. We found that pulmonary contusion severity, as measured by BPC18, was associated with worse respiratory outcomes, and longer ICU and hospital length of stay. In patients with pulmonary contusions, SSRF was not associated with worse outcomes, even when adjusted for injury severity. Moreover, SSRF might be associated with better outcomes for patients with mild to moderate pulmonary contusions.
Some recent studies have suggested that SSRF for patients with pulmonary contusions is safe and effective, which aligns with our results. [23][24][25] The finding that outcomes did not differ for SSRF versus nonoperatively managed patients with severe pulmonary contusions suggests that those severe contusions might negate the benefits of SSRF, as previously has been described. 18  Specifically, pulmonary morbidity such as pneumonia, respiratory failure, and tracheostomy may be driven primarily by the severe contusion in this group rather than the chest wall injury. Potentially, SSRF could mitigate worsening of mild to moderate pulmonary contusions and thereby lead to better clinical outcomes, although this was not demonstrated with our data. Importantly, our results do not support previously stated recommendations that pulmonary contusions are a contraindication to SSRF. 19,20 This is the first study specifically evaluating the clinical outcomes of SSRF in association with pulmonary contusion severity. In addition, a strength of this study is that it accounted for varying degrees of severity of pulmonary contusions in a standardized way on chest CT. Chest CT is highly sensitive to identify pulmonary contusions and is predictive for the need for mechanical ventilation, which, in contrast, is limited when using chest x-rays only. 10 However, to quantify pulmonary contusion severity, multiple methods have been described, mostly based on the volume of the contused lung, but no universal classification currently exists. 15,[26][27][28] Although chest CT is highly sensitive for diagnosing pulmonary contusion even in presence of pneumothorax or pleural fluid, evaluating contusion severity can be challenging. 12 Interobserver variability exists for scoring BPC18, which is a limitation of this study. In addition, pulmonary contusions evolve over time and can worsen in the hours after injury. 10,16 Relying on admission CT only could have caused underestimation of the extent of pulmonary contusions potentially leading to respiratory failure.
Moreover, because of the retrospective nature of the study, comparing the SSRF and nonoperatively managed patients is subject to bias. Although the analysis was adjusted for injury severity by ISS, residual bias by other unmeasured patient or injury characteristics cannot be ruled out. Therefore, the association between SSRF and outcomes for patients with pulmonary contusions in addition to severe rib fractures should be interpreted cautiously because causation cannot be proven with this retrospective cohort. Last, only clinical outcomes were evaluated; for example, biomarkers of systemic inflammation might provide more objective evidence. Multiple rib fractures are related to impaired quality of life, both short-term and long-term. [4][5][6] Consequently, patient-reported quality of life outcomes are at least as important as clinical outcomes for evaluating the effectiveness and safety of SSRF in presence of pulmonary contusions. Future SSRF studies accounting for pulmonary contusion severity are needed to evaluate these missing quality of life outcomes.
In conclusion, our results suggest that pulmonary contusions are not a contraindication to SSRF, regardless of the severity of the contusion. On the contrary, SSRF might be of benefit to clinical outcomes, especially in presence of mild to moderate pulmonary contusions.