The number of displaced rib fractures is more predictive for complications in chest trauma patients

We retrospectively reviewed the trauma registry and medical records between January 2013 and May 2015 at the Chang Gung Memorial Hospital, Keelung, Taiwan. Our hospital is a teaching hospital with 1089 beds and is categorized as an advanced emergency responsibilities hospital by the Ministry of Health and Welfare. There are about 1300 trauma patients admitted to our hospital every year and about one-fifth are referrals. All patients were treated according to the Advanced Trauma Life Support (ATLS) guideline [10]. Whole body computed tomography (CT) was arranged if the patients suffered from major trauma mechanisms (high-speed motor vehicle accident, pedestrian run over by a vehicle, thrown from car, etc.) and had no absolute contraindication. Minor chest trauma patients would be arranged chest radiograph (CXR) and rib view radiograph for the initial survey. Chest CT would also be arranged for patients with a positive chest injury finding (e.g. flail chest, multiple rib fractures, and lung contusion) and for those who needed mechanical ventilation due to receiving surgical interventions. Patients with flail chest, multiple rib fractures, respiratory distress, and unstable vital signs were admitted to the intensive care unit (ICU). The surgical indications for emergent thoracotomy include massive hemothorax with evacuation of more than 1500 mL of blood immediately after tube thoracostomy and persistent bleeding from the chest with 200 cc per hour for consecutive three hours. The surgical indications for video-assisted thoracoscopic surgery (VATS) included retained hemothorax after tube thoracostomy for 3–7 days and pneumothorax with persistent air leak for 3 days after tube thoracostomy. One dedicated trauma registrar recorded all demographic data such as gender, age, index of coexistence disease (ICED) and alcohol consumption [11] of trauma patients in this trauma databank. The records include demographic data, pre- and post-hospital status, trauma mechanisms such as a motorbike, car, bicycle, pedestrian, fall, and others, interventions throughout the emergency department and hospital course, and outcomes such as length of stay and in-hospital mortality.

Two-step inclusion method was adopted in this study: 1) hospitalized patients with evidence of rib fracture were eligible for inclusion review; 2) patients with concomitant severe brain injury, severe splenic injury, severe pelvic injury or severe liver injury (defined as AIS≧4) were excluded for final analysis to simplify potential causal relationship between rib fracture and outcomes. Diagnosis of rib fracture was made by standard CXR, rib view radiograph, or chest CT. All CXR, rib view radiograph, and chest CT were re-examined by the first and the second author separately, and discrepant results were further resolved by consensus meetings. The numbers of displaced and non-displaced rib fractures were recorded separately after the meetings. A displaced rib fracture was defined as a displacement distance at least half of the rib width (Additional file 1: Figure S1a and b). The locations of rib fractures were classified into upper (1st–3rd), middle (4th–9th), and lower (10th–12th). The laterality of rib fractures was recorded as the right side, left side and both sides. The injury severity score (ISS) [12] and abbreviated injury scale (AIS) [13] were also recorded.

Our major outcomes were pulmonary complications, defined as pneumothorax, hemothorax, flail chest, pulmonary contusion, or pneumonia. Secondary outcomes included respiratory failure defined as on ventilator for more than 48 h, tube thoracostomy, and delayed onset complications defined as pneumohemothorax, pneumonia, and pulmonary contusion becoming evident until 24 h after admission.

We calculated RibScore and TTSS for each patient in our study. The Ribscore was the sum of six 1-point variables: (1) six or more rib fractures (2) bilateral fractures (3) flail chest (4) three or more severely displaced fractures (5) first rib fracture and (6) at least one fracture in all three anatomic areas (anterior, lateral, and posterior) [7]. According to the Ribscore, we categorized all patients into three groups: 0–1, 2–3 and 4–6. The TTSS incorporates age, respiratory status, rib fracture numbers, pulmonary contusion and pleural involvement on admission and we categorized the patients according to the TTSS into four groups: 0–4, 5–7, 8–12, and 13–25 [14].

As to the statistical methods, we used Pearson’s x² test and Fisher’s exact test to distinguish the potential risk factors. Statistical significance was defined as a two-tail p-value less than 0.05. Sensitivity, specificity, positive predictive value (PPV) , negative predictive value (NPV), and the 95% confidence interval were calculated to find the recommended cut-off values for clinical utility. We combined the numbers of total and displaced rib fractures to find the best cut-off value. Multivariable logistic regression models were applied to evaluate the performance of the numbers of total and displaced rib fracture adjusting for the severity of the chest trauma using TTSS and Ribscore. Statistical analysis was performed by SPSS (version 17.0; SPSS, Chicago, IL, USA).

We followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement to report this observational study [15]. The institutional review board approved this study (104–7586B) and waived the informed consents owing to the retrospective nature of this study.