SGEM#161: Sternal Fractures – Break on Through to the Other Side – Delayed Complications and Functional Outcomes

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Date: September 21st, 2016

Reference: Racine et al. Delayed complications and functional outcome of isolated sternal fracture after emergency department discharge: a prospective, multicentre cohort study. CJEM Sept 2016

Guest Skeptic: Dr. Chris Bond. Chris is an emergency physician and clinical lecturer at the University of Calgary. He is currently the host of CAEP Casts, which highlights educational innovations from emergency medicine residency programs across Canada. Chris also has his own #FOAMed blog called Standing on the Corner Minding My Own Business (SOCMOB).

Case: A 49-year-old male presents to the emergency department after being in a motor vehicle collision. You diagnose him with an isolated sternal fracture on X-ray. Specifically there are no rib fractures or lung abnormalities identified. He also has a normal ECG and troponin. As you are preparing to discharge him, he asks if there are any potential complications to expect from the injury, and how long he should expect to have pain?

Background: Sternal fractures are often the result of a significant blunt thoracic trauma and have an incidence between 0.33% of all trauma patients (Recinos et al and 3.7% of patients admitted after a motor vehicle accident (Yeh et al).

Poor outcomes in patients with sternal fracture are associated with the severity of other injuries, complications and pre-existing comorbidities (Yeh et al). Many studies have demonstrated that a patient with an isolated fracture of the sternum can be safely discharged from the emergency department after an appropriate investigation (Hossain M, Khoriati et al and Kouritas et al), which should include cardiac biomarkers and ECG (Clancy et al).

Therefore, the clinical significance of isolated sternal fracture has change over the past years and admission is no longer required for those patients. When looking at other minor thoracic injuries discharged from emergency department, delayed hemothorax has been reported as a significant delayed complication (Misthos et al and Plourde et al) and a risk factor for poor functional outcome (Emond et al).

Clinical Question: What are the complications and outcomes of patients with isolated sternal fracture discharged from the emergency department compared to those with other minor thoracic injury?

Reference: Racine et al. Delayed complications and functional outcome of isolated sternal fracture after emergency department discharge: a prospective, multicentre cohort study. CJEM Sept 2016

Population: Patients 16 years and older presenting to the emergency department with minor thoracic trauma defined by the presence of chest abrasion or contusion, or suspected or radiographically confirmed rib fracture.
- Exclusion criteria: The presence of a hemothorax, pneumothorax, lung contusion or any significant cerebral, thoracic, abdominal or extremity injury on their initial emergency department visit; A follow-up not possible; A delay greater than three days between the injury and the emergency department visit.
Intervention: Patients with isolated sternal fracture
Comparison: Those with rib fracture(s) or no fracture
Outcome(s):
- Delayed hemothorax: This was determined by chest x-ray read by a blinded radiologist
- Functional Outcome at 30 and 90 days: This was assessed using a validated instrument called the Medical Outcome Short-Form Health Survey (SF-12). This tool has 12 questions that address eight health elements. The score for each element is measure on a scale from 0-100 with 100 being the best outcome. The data can be aggregated into a global physical health summary and a global mental health summary.

Author’s Conclusions: In this prospective study, we found that 12.5% of patients with sternal fracture developed a delayed hemothorax, but the clinical significance of this remains questionable. The proportion of patients with sternal fracture who had moderate to severe disability was significantly higher than that of patients with other minor thoracic trauma.

Quality Checklist for Observational Study:

Did the study address a clearly focused issue? Yes
Did the authors use an appropriate method to answer their question? Unsure. They assumed that any effusion seen on chest x-ray in the follow-up period was hemothorax. Seems like a safe assumption, but no way of accurately knowing without drainage or CT scan. In the real world, the answer to this might be yes.
Was the cohort recruited in an acceptable way? Yes
Was the exposure accurately measured to minimize bias? Yes.
Was the outcome accurately measured to minimize bias? Yes. They had a blinded radiologist reading the follow-up chest x-rays and used a validated scale to assess functional outcome.
Have the authors identified all-important confounding factors? No. One major confounding factor is the actual accuracy of diagnosing isolated sternal fractures based on plain films alone, given the poor sensitivity of chest x-ray for rib fractures. We don’t know if some people received chest CT scans, while others only received plain films, this could result in inaccurate group assignment.
Was the follow up of subjects complete enough? Yes/No. They had good follow up for delayed hemothorax at two weeks. However, the 90-day follow-up was only 70%.
How precise are the results/is the estimate of risk? Estimate of risk has its precision reduced because of the small sample size. There were 32 patients with isolated sternal fractures and only four developed a delayed hemothorax. (do they have 95% CI for the results to quantify precision? – No)
Do you believe the results? Yes/Unsure. Yes for the delayed hemothorax and unsure for the functional outcome.
Can the results be applied to the local population? Unsure. It will depend on your local population.
Do the results of this study fit with other available evidence? Yes

Key Results: They screened 2,866 patients with 969 included in the study. The mean age was 53 years with 63% being male. There were some differences between the groups (age, gender, mechanism of injury and pre-existing airway disease).

Out of 969 patients, 32 (3.3%) had an isolated sternal fracture, 304 (31.3%) had a rib fracture, and 633 (65.3%) had no fracture.

Motor vehicle crash was the most common cause of sternal fractures (78%) while a fall from the patient’s own height was the number one cause of rib fractures (38%).

Primary Outcome: Delayed hemothorax within 14 days

Total: 112/969 (11.6%)
Sternal Facture Group: 4/32 (12.5%)
Rib Fracture(s) Group: 70/304 (23%)
No Fracture Group: 38/633 (6%)

Notably, none of the four patients with delayed hemothorax in isolated sternal fractures required drainage, while three cases in the rib fractures group did require drainage.

No other major complications and no mortality was observed at 90 days.

Other Primary Outcome: Functional Outcome

Isolated sternal fracture had more significant physical disability at 30 and 90 days as rated on the SF-12 (Medical Outcome-Short Form Health Survey) by patients.

We asked Samuel five questions about his research. He and his supervisor Dr. Marcel Emond response’s are in italics. Listen to the podcast to hear their responses.

Groups
- Differences Between Groups: There were differences between the groups at baseline (ex: age, gender, mechanism). What impact if any do you think this could have on your results?
  - Age and gender differences could have influenced the functional outcome. That is why our statistical analysis for these results were normalized for age and sex. When looking at delayed hemothoraces, one of our collaborators found in another study that age was not a risk factor for this type of complication. The difference regarding the mechanism of injury was expected. It is well reported in the literature that the main mechanism of injury is fall for rib fracture and motor vehicle crash for sternal fracture. The effect of this difference is to our knowledge minimal on the results when talking about isolated thoracic injuries.
- Group Assignment: Chest x-rays are only about 50% sensitive for rib fractures (Hoffstetter et al). How do you know that those with sternal fractures did not have rib fractures and those called negative for any fractures did not have a rib fracture?
  - That’s a very good question. In an ideal situation every patient would have got a CT-Scan as a gold standard investigation but it was not possible in the current design of this study, mainly because of the pragmatic design that tends to reflect day-to-day practice where not all patients get a CT-Scan. We cannot be sure that patients didn’t have rib fracture(s) in the sternal fracture or no fracture group. However, 14 patients were excluded during the follow-up because they were diagnosed with rib fracture(s) on the subsequent chest x-rays. That might have increased the sensitivity.
Small Number of Patients: Only a small number of patients in your study had sternal fractures (32) and even a small number had a delayed hemothorax diagnosed within 14 days (4). These small numbers can limit the precision of your results.
- Yes, absolutely these small numbers limit the precision of our results. Isolated sternal fracture was a rare finding and delayed hemothorax was even rarer. We would have needed a bigger cohort and longer time of recruitment to increase these numbers.
- Nonetheless to say, sternal fracture are often looked for but not that often diagnosed. It is probably one of the largest cohort. It would have taken years and years to get bigger numbers.
No Base-Line Function: You used a validated scale to assess functional status. However, you did not have a baseline level for comparison. Pre-injury functional status is known to be an important factor in assessing post-injury status. Why did you not collect this data?
- This decision was made for practical reason. I totally agree that it would have been better to have these baseline levels. The initial data collection was made by the treating physicians, therefore the decision to minimize the information that was collected initially was made to facilitate the recruitment and minimize the time that clinicians would spend for this data collection.
Outcomes
- Delayed Hemothorax: One of the aims of your study was the incidence of delayed hemothorax but there were other complications observed in follow-up. This included pneumothorax and pneumonia. None were seen in the sternal fracture group. Can you comment on why you focused in on hemothorax?
  - One of collaborators identified delayed hemothorax as a significant risk factor for a poorer functional outcome in another study, along with the number of broken ribs (Plourde et al). We were wondering if delayed complications could impact the functional outcomes, so we focused our interest on the one that seems the most relevant.
- Statistical vs. Clinical Significance: There were some statistical differences identified in your study, however, none of the four patients with sternal fractures who developed a hemothorax required drainage. So how important is the finding?
  - It is a very good question. We don’t have the answer to date. The incidence of delayed hemothorax in the whole cohort was similar to the one reported in other studies looking at delayed complications of minor thoracic injuries. Therefore, we think our finding might not be clinically relevant but further studies will be needed to definitely answer this question.
  - However, we took a pragmatic approach in this study. Drainage was left to the attending emergency physician or surgeon consultant. Under their discretion and a patient centred approach, many factors may have influence this decision whether or not to have drainage. Compared to Europe, we usually drain less hemothorax in North America.
Follow-up
- Lost to Follow-up: Your follow-up for delayed hemothorax was good (92%). The 30-day follow-up for function was not bad (83%) with only a small difference between the groups. However, the 90-day follow up was poor (70%) with big differences between the groups. Only 50% of the sternal fracture patients followed up compared to 80% of the other groups.
  - Yes, this limits the scope of our results for sure. However, patients lost to follow-up had similar baseline characteristics to those with fully available data, potentially limiting the impact of these losses on the results.
- Length of Follow-up for Delayed Hemothorax: Do you think two weeks was long enough to identify all the patients with a delayed hemothorax? You did include one patient in the fractured rib group that did have a hemothorax detected beyond 14 days.
  - We think clinically significant complications would have presented within 14 days. This cut-off was based on a previous study on minor thoracic traumas where they found that all delayed hemothorax associated with rib fractures were detected within 14 days (Misthos et al). Regarding the patient with a hemothorax detected after 14 days, this was a patient that was kept for analysis because he didn’t show up at the 14 days follow-up but at 21 days instead. The decision was made to keep his data for analysis because he didn’t have data for the 14 day follow-up visit. Otherwise he would have been excluded.
- Length of Follow-Up for Functional Outcome: You say in the discussion that previous research has established that pain persists for a mean of almost eleven weeks. Why did you not evaluate functional outcomes beyond 90 days?
  - This decision was simply made for practical reason, to make the follow-up easier and minimize the lost to follow-up.

Comment on authors’ conclusion compared to SGEM Conclusion: We agree with the authors’ conclusion about the incidence of delayed hemothorax in patients with isolated sternal fractures that are discharged home. We are less confident about their conclusions about disability.

SGEM Bottom Line: Patients discharged home with isolated sternal fractures have a risk of delayed hemothorax. These are painful injuries and patients should be provided with adequate analgesia and follow-up.

Case Resolution: He is discharged from the emergency department with adequate pain control, warned about when to return and set expectations on how long he might expect to have pain.

Clinical Application: We should be sure to inform patients with sternal fractures of reasons to return to the emergency department and adequately manage pain for these patients.

Dr. Chris Bond

What do I tell my patient? About one in eight patients with a sternal fracture will develop bleeding in the chest in the next two weeks. If you develop increasing shortness of breath, chest pain, fever or are otherwise concerned please come back to the emergency department.

You can take acetaminophen and/or an NSAID for the pain. I will also give you a prescription for an opiate to be used only if needed. You can expect to have some pain and difficulty with physical function for weeks or even months.

Keener Contest: The last episode winner was Chip Lange a Physician Assistant practicing in ‪Rural Missouri. Chip has his own #FOAMed project called TotalEM. He knew the first practical biomarker used for diagnosing MI was serum glutamic oxaloacetic transaminase (SGOT) that is now called aspartate amino-transferase (AST).

Listen to the podcast for this weeks’ question. If you think you know the answer send it to TheSGEM@gmail.com with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

References:

Recinos G, Inaba K, Dubose J, et al. Epidemiology of sternal fractures. Am Surg 2009;75(5):401-4.
Yeh DD, Hwabejire JO, DeMoya MA, et al. Sternal fracture—an analysis of the National Trauma Data Bank. J Surg Res 2014;186(1):39-43
Hossain M. 45-year-old male from an RTA with isolated sternal fracture: immediate discharge or hospital admission? Evid Based Med 2009;14(5):134-5.
Khoriati AA, Rajakulasingam R, Shah R. Sternal fractures and their management. J Emerg Trauma Shock 2013;6(2):113-6.
Kouritas VK, Zisis C, Vahlas K, et al. Isolated sternal fractures treated on an outpatient basis. Am J Emerg Med 2013;31(1):227-30.
Clancy K, Velopulos C, Bilaniuk J, et al., Screening for blunt cardiac injury: An Eastern Association for the Surgery of Trauma practice management guideline, J of Trauma Acute Care Surgery, 2012, 73(5); S301-306.
Misthos P, Kakaris S, Sepsas E, et al. A prospective analysis of occult pneumothorax, delayed pneumothorax and delayed hemothorax after minor blunt thoracic trauma. Eur J Cardiothorac Surg 2004;25(5):859-64.
Plourde M, Émond M, Lavoie A, et al. Cohort study on the prevalence and risk factors for delayed pulmonary complications in adults following minor blunt thoracic trauma. CJEM 2014;16(2):136-43.
Émond M, Sirois MJ, Guimont C, et al. Functional impact of a minor thoracic injury: an investigation of age, delayed hemothorax, and rib fracture effects. Ann Surg 2015;262(5): 1115-22.
Hoffstetter et al. Diagnostic significance of rib series in minor thorax trauma compared to plain chest film and computed tomography. Journal of Trauma Management & Outcomes 2014, 8:10.