Which comorbidities matter most in patients with multiple rib fractures? An analysis of the national inpatient sample :Christopher W Towe, Avanti Badrinathan, Vanessa P Ho, Katelynn C Bachman, Stephanie G Worrell, Matthew L Moorman, Philip A Linden, Fredric M Pieracci, The Journal of Cardiothoracic Trauma

ORIGINAL ARTICLE
Year : 2021 | Volume : 6 | Issue : 1 | Page : 22--27

Which comorbidities matter most in patients with multiple rib fractures? An analysis of the national inpatient sample

Christopher W Towe¹, Avanti Badrinathan¹, Vanessa P Ho², Katelynn C Bachman¹, Stephanie G Worrell¹, Matthew L Moorman³, Philip A Linden¹, Fredric M Pieracci⁴,
¹ Department of Surgery, Division of Thoracic and Esophageal Surgery, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
² Department of Surgery, Division of Trauma, Critical Care, Burns and Acute Care Surgery, MetroHealth Medical Center, Cleveland, OH, USA
³ Department of Surgery, Division of Trauma, Critical Care and Acute Care Surgery, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
⁴ Department of Surgery, Denver Health Medical Center, University of Colorado School of Medicine, Denver, CO, USA

Correspondence Address:
Christopher W Towe
Department of Surgery, Division of Thoracic and Esophageal Surgery, University Hospitals Cleveland Medical Center, 11100 Euclid Avenue, Cleveland, OH 44106-5011
USA

Abstract

Background: Increased age and number of rib fractures are known to increase the risk of mortality. The impact of comorbidities on the outcomes of patients with rib fractures has not previously been described. We hypothesized that specific medical comorbidities are associated with increased risk of morbidity and mortality following rib fracture. Methods: Patients with multiple rib fractures or flail chest were identified in the National Inpatient Sample by ICD-10 code from the 4^th quarter of 2015 through 2016. Comorbidities were categorized into Elixhauser comorbidity groups, and injury severity was estimated using the Injury Severity Score (ISS). The composite adverse outcome was defined as death, pneumonia, tracheostomy, or discharge to a short-term acute care facility. Multivariable logistic regression was performed with covariates chosen through backward selection from the univariate model to determine the relationship of outcomes to demographic variables and comorbidities with alpha set to 0.001. Results: Totally 26,289 patients met inclusion criteria. Composite adverse outcomes occurred in 5,132 (19.5%) patients. Profound ISS (OR 6.013), severe ISS (odds ratio [OR] 2.569), fluid and electrolyte disorder (OR 2.471), and paralysis (OR 2.372) were most associated with adverse outcomes. Within causes of injury, motor vehicle was associated with increased risk of adverse outcome (OR 1.322). Flail chest was also independently associated with adverse outcome (OR 1.816). Conclusion: Morbidity and mortality following rib fracture occurred in approximately one-fifth of patients, especially those with high ISS or associated medical comorbidities. This data can be used for risk stratification and identification of high-risk patients for escalation of care.

How to cite this article:
Towe CW, Badrinathan A, Ho VP, Bachman KC, Worrell SG, Moorman ML, Linden PA, Pieracci FM. Which comorbidities matter most in patients with multiple rib fractures? An analysis of the national inpatient sample.J Cardiothorac Trauma 2021;6:22-27

How to cite this URL:
Towe CW, Badrinathan A, Ho VP, Bachman KC, Worrell SG, Moorman ML, Linden PA, Pieracci FM. Which comorbidities matter most in patients with multiple rib fractures? An analysis of the national inpatient sample. J Cardiothorac Trauma [serial online] 2021 [cited 2023 Jun 1 ];6:22-27
Available from: https://www.jctt.org/text.asp?2021/6/1/22/333273

Full Text

Introduction

There is increasing awareness that rib fractures are associated with complications such as death and respiratory failure. While several studies have examined the association between age and the morbidity of rib fractures, the association of comorbid medical conditions has not been described.[1],[2],[3],[4],[5] Age is often a proxy for chronic medical conditions and frailty, both of which contribute to mortality in traumatic injuries.[6],[7] The purpose of this study was to evaluate the impact of individual medical conditions on the morbidity of rib fractures. We hypothesize that specific medical comorbidities would be associated with adverse outcomes.

Methods

Data source

The National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), and Agency for Healthcare Research and Quality (AHRQ) were used to analyze patients who were hospitalized with rib fractures in 2016.[8] Adult patients (>18 years) were included in the analysis if they had a diagnosis of either multiple rib fractures or flail chest. The NIS database is a part of the HCUP and maintained by the AHRQ. The NIS includes a weighted sample of hospital admissions across the United States. The NIS only includes data from inpatient stays, not individual patients. Conditions, procedures, and diagnoses occurring during a specific inpatient hospital encounter are captured in the NIS. Records of events and diagnoses before or after the stay are not available and not included in this analysis.

Study population

We included all patients ≥18 years with a diagnosis of multiple rib fractures (defined as >1 rib fracture) or flail chest rib fracture due to blunt trauma in the 2016 NIS database. The patients were identified using ICD 10th (ICD-10) revision codes. The ICD-10 codes “base” for multiple rib fractures were S22.4, S22.41, S22.42, S22.43, S22.49, and for flail chest rib fracture was S22.5. Patients with diagnoses of multiple fractures and flail chest were categorized as flail. Blunt trauma was defined using an external cause of injury codes and included codes for fall (EXT003), machinery (EXT006), motor vehicle (MVC) traffic (EXT007), pedal cyclist (EXT008), pedestrian (not motor vehicle traffic [MVT]) (EXT009), transport (not MVT) (EXT010), natural/environmental (EXT011), and struck by/against (EXT016).

Demographic variables, comorbidities, and Injury Severity Score (ISS) were also extracted from the NIS database. Age is uniformly truncated at age 90 with all patients >90 years analyzed as 90. Comorbidity was characterized by the Elixhauser measure, which is a categorization of medical comorbidities into 31 conditions and is thought to be a better predictor of mortality than the Charlson Comorbidity Index.[9],[10],[11] The Elixhauser comorbidity variables were extracted using ICD-10 diagnosis coding using HCUP comorbidity software (HCUP Comorbidity Software, 2008). ISS score was also estimated using ICD-10 codes using the open-access program ICDPIC-R.[12] ISS was further categorized into mild (≤8), moderate (9–15), severe (16–25), and profound (≥25).[13] Mechanism of injury was categorized as MVC or other using external cause of injury codes.

Outcome variable

The primary outcome of interest was a composite of adverse outcomes associated with rib fractures. The composite outcome was as a composite of death, pneumonia, tracheostomy, or discharge to a short-term acute care hospital. Death was defined as death at the time of discharge. Pneumonia and tracheostomy were collected from ICD-10 codes and only represent these complications from the primary admission. Readmission data are not collected in the NIS.

Statistical analysis

Demographic and clinical characteristics were summarized using descriptive statistics. Univariate analyses were performed to determine the association of demographic variables, comorbidities, and injury characteristics to the composite adverse outcome using Chi-square test or rank-sum test as appropriate. Multivariable regression was performed using backward selection of covariates from univariate modeling with α ≤ 0.001. All statistical analyses were performed using Stata version 16.0 statistical software (StataCorp, College Station, TX, USA). This study was considered exempt from IRB approval because the data are deidentified.

Results

A total of 26,289 patients with either multiple rib fractures or flail chest were included in the analysis. Using the weighted survey methods, these patients are estimated to represent 131,445 patient admissions (95% confidence interval 123,942–138,947). Multiple fractures occurred in 25,268 (96.1%) and flail chest in 1,021 (3.9%). Demographic characteristics for the cohort are shown in [Table 1]. The distribution of age is shown in [Figure 1] and demonstrates that 46.7% of patients with rib fractures are older than 65 years, and 23.0% are older than 80 years. While the dominant mechanism of injury is MVC for younger patients, patients older than 70 are more likely to be admitted after fall.{Table 1}{Figure 1}

The composite adverse outcome of death, pneumonia, tracheostomy, or discharge to a short-term acute care hospital occurred in 5,132 (19.5%). Death occurred in 1,162 (4.4%). The average length of hospitalization was 4 days (interquartile range 3–8). The outcomes of patients are shown in [Table 2].{Table 2}

Several factors were associated with adverse outcomes in univariate analysis [Table 3]a. Older age was associated with adverse outcomes, as were several medical comorbidities, including heart failure, peripheral vascular disease, paralysis, liver failure, and renal failure. Several variables were not associated with adverse outcome, including insurance type, whether a patient received care at an academic institution, and comorbidities including peptic ulcer disease. Increasing number of Elixhauser comorbidities were also associated with adverse outcomes. Both increasing ISS and increasingly severe ISS category were associated with adverse outcomes as well.{Table 3}

Multivariable regression was performed using factors which were identified as associated with adverse outcomes in the univariate analysis. The results of multivariable regression are shown in [Table 3]b. In this model, where covariates were chosen through backward selection from the univariate model, the covariates most associated with the composite adverse outcome were profound ISS (≥25) category (odds ratio [OR] 6.013, P < 0.001), severe ISS (16-24) category (OR 2.569, P < 0.001), fluid and electrolyte disorder (OR 2.471, P < 0.001), and paralysis (OR 2.372, P < 0.001). Some comorbidities were inversely associated with adverse outcomes, including hypertension and hypothyroidism. Within injury type, MVC was associated with increased risk of adverse outcome (OR 1.322, P < 0.001). Flail chest was also independently associated with adverse outcome (OR 1.816, P < 0.001).

Conclusion

Rib fractures account for more than 200,000 ER visits and an additional 130,000 hospital admissions.[8] Some studies have estimated more than 10% of all trauma admissions include rib fractures.[1] Rib fractures are common in older adults, with nearly half of patients (47%) in this study over 65 years and nearly a quarter (23%) over 80. Although previous studies have examined the effect of age on outcomes of rib fractures, comorbidity has not been as rigorously studied. We have identified the relative contribution of multiple comorbidities to adverse outcomes (death, transfer to short-term hospital, tracheostomy, and/or pneumonia) of patients with rib fractures following blunt trauma. Specifically, increasing ISS, paralysis or other neurological disorder, fluid and electrolyte disturbances, and flail chest were main contributors to poor clinical outcome. These findings have not been described previously. One study of the association of comorbidity and outcomes did not demonstrate the association of most comorbidities with adverse outcome, but this study was likely underpowered to detect an association.[3]

Several risk stratification scores have been described in patients with rib fractures. Most are purely radiographic, some include demographic variables such as age, and most recently, dynamic scores that include daily pulmonary physiology variables have been described.[14],[15],[16] None of these scoring systems take into consideration a patient's underlying comorbidities. Incorporation of patient comorbidities will strengthen risk stratification models and help guide the provision of resources such as intensive care unit (ICU), locoregional anesthesia, and surgical stabilization of rib fractures (SSRF).

Several clinical trials suggest that SSRF may improve outcomes of select patients with rib fractures. Randomized trials of SSRF in patients with flail chest have shown that SSRF improves outcomes of pneumonia, duration of mechanical ventilation, total length of stay, and ICU length of stay.[17] These trials have led to EAST practice management guidelines that support the SSRF in patients with flail chest.[18],[19] More recently, the chest wall injury society (CWIS) nonflail trial suggests that there are additional pain and quality of life benefits to SSRF in patients with nonflail injuries.[20] Other nonrandomized studies have also suggested benefits to rib fixation in other cohorts, including patients >65 years.[21] It is unclear whether SSRF is beneficial in other cohorts, and some studies have not shown benefit to SSRF.[22] The authors believe that rib fixation may have benefit in other patients who are at high risk for adverse outcomes and advocate for further research in this area. The data presented here do not suggest benefit to SSRF in patients with elevated risk of adverse events. We advocate for use of these comorbidities in future studies and for consideration in future trial design, especially in older adults.

This analysis has several limitations. Foremost, the nature of this study is retrospective and may not include variables which are associated with the outcome of interest. Specific injuries, for example, such as traumatic amputations are certainly associated with morbidity and are not included in this analysis. These data also cannot be used to measure other adverse outcomes, such as readmission or death after discharge, which may significantly bias the results. Furthermore, the method of data abstraction has significant limitations. For example, it is possible that medical comorbidities identified by patients during their admission were caused by their injuries, not preexisting. This may confound the findings of this analysis and limit the generalizability. Finally, this analysis has not considered surgical stabilization of rib fractures, which may have affected patient outcomes.

This is the largest study to date of the morbidity of rib fractures in the United States. We believe that the impact of rib fractures on patients is significant, and the contribution of comorbidities on the outcome of patients with rib fractures may be underrecognized. We advocate for ongoing research in rib fracture care and the role of surgery in the care of these patients.

Ethical clearance

This study was considered exempt by the IRB because the data are deidentified.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1	Ziegler DW, Agarwal NN. The morbidity and mortality of rib fractures. J Trauma. 1994;37:975-9.
2	Bulger EM, Arneson MA, Mock CN, Jurkovich GJ. Rib fractures in the elderly. J Trauma. 2000;48:1040-6; discussion 6-7.
3	Barnea Y, Kashtan H, Skornick Y, Werbin N. Isolated rib fractures in elderly patients: mortality and morbidity. Can J Surg 2002;45:43-6.
4	Bergeron E, Lavoie A, Clas D, Moore L, Ratte S, Tetreault S, et al. Elderly trauma patients with rib fractures are at greater risk of death and pneumonia. J Trauma 2003;54:478-85.
5	Stawicki SP, Grossman MD, Hoey BA, Miller DL, Reed JF, 3^rd. Rib fractures in the elderly: a marker of injury severity. J Am Geriatr Soc 2004;52:805-8.
6	Joseph B, Pandit V, Zangbar B, Kulvatunyou N, Tang A, O'Keeffe T, et al. Validating trauma-specific frailty index for geriatric trauma patients: a prospective analysis. J Am Coll Surg. 2014;219:10-7 e1.
7	Ondeck NT, Bovonratwet P, Ibe IK, Bohl DD, McLynn RP, Cui JJ, et al. Discriminative Ability for Adverse Outcomes After Surgical Management of Hip Fractures: A Comparison of the Charlson Comorbidity Index, Elixhauser Comorbidity Measure, and Modified Frailty Index. J Orthop Trauma. 2018;32:231-7.
8	National Inpatient Sample (NIS). Healthcare Cost and Utilization Project (HCUP) [Internet]. Agency for Healthcare Research and Quality. 2012. Available from: www.hcup-us.ahrq.gov/nisoverview.jsp.
9	Baker SP, O'Neill B, Haddon W, Jr., Long WB. The injury severity score: A method for describing patients with multiple injuries and evaluating emergency care. J Trauma. 1974;14:187-96.
10	Elixhauser A, Steiner C, Harris DR, Coffey RM. Comorbidity measures for use with administrative data. Med Care 1998;36:8-27.
11	Chu YT, Ng YY, Wu SC. Comparison of different comorbidity measures for use with administrative data in predicting short- and long-term mortality. BMC Health Serv Res. 2010;10:140.
12	Clark DE, Black AW, Skavdahl DH, Hallagan LD. Open-access programs for injury categorization using ICD-9 or ICD-10. Inj Epidemiol. 2018;5:11.
13	Bolorunduro OB, Villegas C, Oyetunji TA, Haut ER, Stevens KA, Chang DC, et al. Validating the Injury Severity Score (ISS) in different populations: ISS predicts mortality better among Hispanics and females. J Surg Res. 2011;166:40-4.
14	Chapman BC, Herbert B, Rodil M, Salotto J, Stovall RT, Biffl W, et al. RibScore: A novel radiographic score based on fracture pattern that predicts pneumonia, respiratory failure, and tracheostomy. J Trauma Acute Care Surg. 2016;80:95-101.
15	Holcomb JB, McMullin NR, Kozar RA, Lygas MH, Moore FA. Morbidity from rib fractures increases after age 45. J Am Coll Surg. 2003;196:549-55.
16	Hardin KS, Leasia KN, Haenel J, Moore EE, Burlew CC, Pieracci FM. The Sequential Clinical Assessment of Respiratory Function (SCARF) score: A dynamic pulmonary physiologic score that predicts adverse outcomes in critically ill rib fracture patients. J Trauma Acute Care Surg. 2019;87:1260-8.
17	Coughlin TA, Ng JW, Rollins KE, Forward DP, Ollivere BJ. Management of rib fractures in traumatic flail chest: a meta-analysis of randomised controlled trials. Bone Joint J. 2016;98-B(8):1119-25.
18	Kasotakis G, Hasenboehler EA, Streib EW, Patel N, Patel MB, Alarcon L, et al. Operative fixation of rib fractures after blunt trauma: A practice management guideline from the Eastern Association for the Surgery of Trauma. J Trauma Acute Care Surg. 2017;82:618-26.
19	Simon B, Ebert J, Bokhari F, Capella J, Emhoff T, Hayward T, 3^rd, et al. Management of pulmonary contusion and flail chest: An Eastern Association for the Surgery of Trauma practice management guideline. J Trauma Acute Care Surg. 2012;73(5 Suppl 4):S351-61.
20	Pieracci FM, Leasia K, Bauman Z, Eriksson EA, Lottenberg L, Majercik S, et al. A multicenter, prospective, controlled clinical trial of surgical stabilization of rib fractures in patients with severe, nonflail fracture patterns (Chest Wall Injury Society NONFLAIL). J Trauma Acute Care Surg. 2020;88:249-57.
21	Fitzgerald MT, Ashley DW, Abukhdeir H, Christie DB, 3^rd. Rib fracture fixation in the 65 years and older population: A paradigm shift in management strategy at a Level I trauma center. J Trauma Acute Care Surg. 2017;82:524-7.
22	Beks RB, Reetz D, de Jong MB, Groenwold RHH, Hietbrink F, Edwards MJR, et al. Rib fixation versus non-operative treatment for flail chest and multiple rib fractures after blunt thoracic trauma: a multicenter cohort study. Eur J Trauma Emerg Surg 2019;45:655-63.